OIL POLLUTION MONITORING - European Space Agency · oil dumped during cleaning operations). Approximately 2 million tons of oil are introduced annually by such operations, equivalent

OIL POLLUTIONMONITORING

Estimate of the sourcesof oil spills at sea The Need for Better

InformationThe search for oil reserves offshore ismoving into deeper and deeper waters,and crude oil and oil products are beingtransported across the globe inincreasingly larger tankers. As a result, oilspills pose a serious threat to the ecologyof the World’s oceans. The amount of oilspilled annually worldwide has beenestimated at more than 4.5 million tons.

The biggest contributor to oil pollution inthe World’s oceans (some 45%) isoperational discharges from tankers (i.e.oil dumped during cleaning operations).Approximately 2 million tons of oil areintroduced annually by such operations,equivalent to one full-tanker disasterevery week. Only 7% of the oil in the seacan be directly attributed to accidents.Land-based sources such as urban wasteand industrial discharges, which reachthe ocean via rivers, are also a majorcontributory factor.

International Commissions have beenformed and Conventions agreed in anattempt to curb marine pollution. TheOslo-Paris Commission (OSPARCOM) forthe environmental protection of theNorth East Atlantic, and the UnitedNations Convention on the Law of theSea (UNCLOS) in which more than 150countries participate, are just twoexamples of such co-operative efforts. Allof the countries bordering the Baltic Seaand the members of the EuropeanEconomic Community signed the HelsinkiCommission (HELCOM) Agreement in

1992 to protect their coasts. In addition,the North Sea countries have committedthemselves to intensifying the battleagainst oil pollution. In the framework ofthe Bonn Agreement (1969), almost dailysurveillance is carried out to check forpollution on the North Sea ContinentalShelf. The signatories of the InternationalConvention for the Prevention ofPollution from Ships (MARPOL 73/78)Agreement are obliged to ensure thatports provide reception facilities for ships’waste, and limitations are imposed to tryto protect ecologically sensitive areasagainst oil discharges.

Although the oil industry is fully aware ofthe international laws and the risksconnected with marine pollution, there isstill ample evidence of numerous repeatoffenders. Many countries cannot affordan adequate surveillance programme.Coast-guard personnel and ship and

OIL POLLUTIONMONITORING

A ship discharging oil

The Limitations of TraditionalTechniquesAn operational pollution-monitoringscenario based only on aircraft and shipsurveillance has several drawbacks:• The time delay between an illegal

discharge and its detection does not permit a successful prosecution in most of the cases, unless the culprits are caught “red-handed”.

• Poor weather conditions can prevent an aircraft from flying over the area.

• The resources available for airborne surveillance often allow only a small fraction of coastal waters to be surveyed.

• Evidence based only on SLAR data is often deemed insufficient in a court of law.

aircraft crews frequently report sightingsof oil spills, but the percentage of spillsdetected is still relatively low. Surveillanceis carried out in some areas usingremote-sensing aircraft. The Side-LookingAirborne Radar (SLAR) and radiometerson these aircraft detect pollution underdifferent conditions and over wider areasthan ships’ observations.

National Pollution Control Authoritiessuch as the National Coast Guard orcentres for environmental protection havethree main roles in terms of oil-spilldetection:• early warning• legal prosecution• provision of pollution statistics.

Identification of the discharge source andphotographic documentation arerequired quickly both for the legalprosecution and the prevention ofenvironmental damage.

The Benefits of Space-BasedMonitoringToday, the availability of data from Earth-observation satellites offers the possibilityto complement and optimise surveillancestrategies, allowing a more cost-effectiveapproach to oil-pollution monitoring.Space-acquired Synthetic Aperture Radar(SAR) data can complement current aerialsurveillance strategies both by providingcoverage over areas not easily surveyedwith aircraft, and also by providingsynoptic views of large areas. This raisesthe likelihood of immediate interventionbeing feasible, makes the operations as awhole more cost-effective, anddramatically increases the size of the areathat can be routinely surveyed.

The introduction of satellite data as anadditional information source has severaldistinct advantages:• The combined use of satellites, ships

and aircraft for surveillance increases the chances of early detection of oil spills and fast clean-up operations, preventing further environmental damage.

• By regularly monitoring large areas, deeper analysis can be performed and more accurate statistics on the occurrence of oil slicks can be provided.

• Oil seeping naturally from the sea floor can be detected, and its occurrences carefully monitored.

• A better overview of oil spreading, and therefore a source of input to oil drift models, can be obtained.

Confirmed oil slicks inthe North Sea detectedby the ERS-1 SAR on 31 March 1996

The Contribution of ERS SARWith the advent of the European RemoteSensing Satellite (ERS) missions inparticular, the Earth is orbited once every100 minutes at an altitude of 780 km.The “nominal” spatial resolution of theERS data is 25 m x 25 m, but for oil-spilldetection “low-resolution” images of 100 m x 100 m are more than sufficient,reducing the data content of each imageto about 2 Mbytes. This type of image caneasily be made accessible via the Internet.

Experiments have been carried out toassess qualitatively and quantitatively thepotential of ERS SAR data for oil-spilldetection. It can be stated as a result thatthe detection capability of the space-borne SAR is comparable to that of theSLAR systems used in today’s maritimeairborne surveillance programmes.

The presence of an oil film on the seasurface damps out the small waves dueto the increased viscosity of the top layerand drastically reduces the measuredbackscattered energy, resulting in darkerareas in SAR imagery. Use of the ERS SARlow- resolution images has demonstratedthe satellites’ ability to detect even verythin pollution layers for low wind speedsof 3-4 m/s and thick oil emulsions for windspeeds up to 12 m/s. Slicks as small as0.1 km2 in area can be detected. Pollutantsthat can be identified by ERS SAR includecrude-oil emulsions, run-off water fromacidic pitch deposits on land, drillingfluids from offshore oil rigs, waste from fish-production plants, and fish fat remainingon the sea surface from trawler catches.

N 58° 17´ E 017° 36´

NFLIGHTDIRECTION

LOOKDIRECTION

SCALE: 1 cm = 7.4 km

An oil slick off theDutch coast asobserved simultaneouslyby a SLAR-equippedsurveillance aircraft(top), and by the ERS-1SAR (bottom). Theshape of the slickappears identical in thetwo images

Examples of Space-BasedApplicationsAn operational spill-monitoringservice in Norway*Since the launch of ERS-1 in 1991, aservice affording near-real-time access toERS SAR data has been offered by theTromsø Satellite Station in northernNorway, as part of the Norwegian SpaceCentre’s national ERS-l programme. Basedon this activity, a near-real-time oil-spillmonitoring service has been establishedfor the Norwegian Pollution ControlAuthority (SFT), a governmental expertagency belonging to the NorwegianMinistry of the Environment.

* The development ofthe service provided bythe Tromsø SatelliteStation has beensupported by a numberof institutions, includingthe Norwegian SpaceCentre (NSC), theNorwegian PollutionControl Authority(SFT), the NorwegianDefence ResearchEstablishment (NDRE),the US Marine SpillsResponse Corporation(MSRC), the oilcompanies Statoil andESSO, and ESA.Recipients of near-real-time data include theDutch North SeaDirectorate (NSD), SFT,and pollution-controlauthorities in Sweden,Finland, the UnitedKingdom, Poland andEstonia.

The Norwegian oil-spill-service coverage area(blue) and nationalhigh-priority area (red).ERS SAR data for theblue and red areas areanalysed in near-real-time

However, SAR (and airborne SLAR)scenes require careful interpretationbecause:• with low wind speeds, dark areas

might not be oil slicks but merely local wind effects or natural oil films, causingfalse alarms unless experienced image interpreters or well-tuned classification algorithms and wind information are employed

• with very high wind speeds, the pollutant may mix rapidly with the sea water, leaving no surface effect to be detected.

On a SAR image, a polluting ship can bespotted but not identified, for which anaircraft overflight or knowledge of theship’s positional record is needed.Confirmation of a slick detected bysatellite is also needed for prosecutionpurposes in a court of law (spilling ship)or for implementing pollutioncountermeasures (large slicks).

The concept of theNorwegian oil-spilldetection service, fromreception and analysisof the data at theTromsø Satellite Station,through early-warningalerts, and aircraftoperations by theNorwegian PollutionControl Authority (SFT)

The Tromsø Satellite Station serviceincludes the near-real-time analysis of ERSSAR data collected over Norwegianwaters and the provision to the PollutionControl Authority of relevant oil-spilllocation information within one hourafter satellite overpasses. A 100 km x 100 kmSAR image is generated at the station in6-8 minutes. An average of 300 such ERSscenes from the service area are analysedper month by the highly trainedoperators. The reporting is based onhuman, computer-supported analysis andinterpretation. Reliability is furtherimproved through the use of additionalmeteorological, geographical andhistorical information.

The Pollution Control Authority’ssurveillance-aircraft operations are

planned and co-ordinated based on thetimings of the ERS overpasses. The Stationoperators are in direct contact with theaircraft crew, which allows flight-pathdeviations to be made to verify satellite-detected slicks.

The extent of the area monitored, incombination with the near-real-timedelivery of information, are just two ofthe advantages of the service beingprovided. ERS SAR data collected over theneighbouring waters of other NorthernEuropean countries are also analysed atthe Tromsø Station and the relevantnational authorities are notified eitherdirectly or via the Norwegian PollutionControl Authority of any oil spillsdetected.

All slicks detected by ERS-1 inthe Dutch North Sea duringthe second half of 1993 (inred). Green points mark thepositions of the oil platforms,whilst blue crosses show thepositions of the monitoringstations. A clear correlation isapparent between thepositions and directions of theslicks and the locations of theshipping lanes

inspections can be performed at shortnotice, but are also carried out randomly.Restrictions are imposed, however, bythe number of possible flights, the areathat can be covered, and the prevailingweather conditions.

NSD currently receives low-resolution ERSimages on an operational basis from theTromsø Satellite Station two or three timesper week, with a delay of just one to oneand a half hours after data reception atthe Station. Such information isfundamental for coordinated interventionby modifying the flight plans of theremote-sensing aircraft to verify featuresdetected in ERS data.

The Dutch experienceSince the nineteen sixties, the extractionof oil and gas has become an importantNorth Sea industry. Over 450 fixedproduction platforms have been installed,which are connected to production wells,to distribution points and to the shore.More than 650 pipelines have alreadybeen laid, ranging in length from 100 mto 1500 km.

The Dutch part of the North Sea ispatrolled daily by an aircraft operated bythe North Sea Directorate (NSD) of theRijkswaterstaat, with the aim of detectingoil spills and discharges from ships andplatforms. About 1200 flight hours aretypically scheduled per year, and

“Quick look” imagederived from the ERS-2 SAR. Based onnight data acquisition,the image reveals illegaloil discharges in theMediterranean as darklinear structures

Cost/Benefit ConsiderationsCost/benefit ratios and cost-effectivenesshave been shown to improve when oil-pollution surveillance is based on acombination of spaceborne and airborneoperations. The use of one aircraft, twoaircraft, and a combination of ERS SARdata (covering 8.4 million km2) and oneaircraft (9.6 million km2) were consideredfor oil-spill monitoring of the 18 millionkm2 area covered annually in the NorthSea. An aircraft equipped with a SLAR canmonitor roughly 15 000 km2 per hourunder nominal conditions. The localweather conditions permit an average offour days of coverage per week, withapproximately four flight hours per day,resulting in a daily coverage of about 60 000 km2. The costs, the time horizon(set to twenty years), as well as the socialimpact have been taken into account inthe evaluation. Social costs and benefitswere calculated for all involved groups ofservice providers, end users, potentialpolluters (e.g. oil companies, shipping,coastal industry).

The results of conservative nett-benefitcalculations show that the benefit-to-costratio varies from 2 to 15 using two aircraft,and from 3 to 22 for the combinedsatellite plus one aircraft scenario, withthe most probable figures lying in theupper ranges of these intervals. Theranking of the two alternatives wasconfirmed by the cost-effectivenessanalysis, which gave estimated costs persquare kilometre of 0.09 and 0.06 ECUfor two aircraft and the aircraft/satellitecombination, respectively.

Future OutlookNew technologies for fast SAR processingare being developed which will reducethe delivery time for satellite imagery stillfurther. Constant improvement of slick-detection algorithms implemented ondedicated work stations will increase thelevel of confidence in spill detection andhence reduce the likelihood of falsealarms.

The combined use of data from the ERSsatellites and Radarsat already providesdaily coverage of a large percentage ofthe coastal oceans. ESA’s forthcomingEnvisat mission, carrying among otherinstruments an advanced SAR, willprovide images covering areas of up to160 000 km2, both contributing to aneven more cost-effective oil pollutionmonitoring service and securing datacontinuity for the years to come.

AcknowledgementsThe support provided by the TromsøSatellite Station, the North Sea Directorateof Rijkswaterstaat (NL), the NetherlandsRemote-Sensing Board (BCRS), and theMunich Re insurance company (D) isgratefully acknowledged.

Contact Addresses For further information on projectsreferred to in this fact sheet:

Tromsø Satellite StationPrestvannveien 38N-9005 Tromsø NorwayPhone: (47) 77 68 48 17Fax: (47) 77 65 78 68Internet Home Page: http://www.tss.no/

North Sea Directorate RijkswaterstaatKoopmansstraat 1Postbus 58072280 HV Rijswijk, The NetherlandsPhone: (31) 70 3366600Fax: (31) 703900691Internet Home Page:http://www.minvenw.nl/

For further information on ERSdata applications:

Remote Sensing Exploitation DivisionData Utilisation SectionESRINVia Galileo Galilei00044 Frascati, ItalyTel: +(39) 6 94180626 or 625

For further information on the ERSProgramme, mission planning, datacatalogues:

Remote Sensing Exploitation DivisionERS Help DeskESRINVia Galileo Galilei00044 Frascati, ItalyTel: +(39) 6 94180666Fax: +(39) 6 94180272e-mail:[email protected]

For information on ERS productsand services (ERS Consortium):

EURIMAGE Customer Services Via Galileo Galilei00044 Frascati, ItalyTel.: +(39) 6 94180741/752/760/776 Fax: +(39) 6 9416772e-mail: [email protected] WWW: http://www.eurimage.it

SPOT Image 5 rue des Satellites31030 Toulouse, France Tel.: +(33) 562194040 Fax: +(33) 562194011 WWW: http://www.spotimage.fr

RADARSAT INTERNATIONAL3851 Shell Road, Suite 200 Richmond, British Columbia Canada V6X 2W2 Tel: (1) 604 2314970Fax: (1) 604 2440404e-mail: [email protected]: http://www.rsi.ca

ESA Publications Divisionc/o ESTEC, PO Box 299, 2200 AG Noordwijk, The NetherlandsTel. (31) 71 565 3400 - Fax (31) 71 565 5433

Prepared by:Remote Sensing Exploitation DivisionESRIN

BATHYMETRICMAPPING

A survey ship engagedin a traditionalbathymetric survey

The Need for BetterInformationBathymetric surveys are required for avariety of purposes at widely ranginglocations. End users include construction,oil, pipeline and cable companies as wellas local and national government users(harbour and shipping control authorities,resource-mapping agencies, coastal-protection agencies, etc.). The market istherefore considerable. The continuingneed for accurate bathymetricinformation, for example by harbour-control authorities which require shippinglanes to be checked every few months,means that the demand for such servicescan be expected to remain high for theforeseeable future.

Typical requirements for coastalbathymetry data are:

• Depth accuracy: better than 30 cm r.m.s. error, although for particular users this can be relaxed (e.g. 1-2 m for Admiralty charts)

• Position accuracy: better than 40 m • Updating: dependent on particular

end-user - some surveys must be repeated every four to six months, whilst others need only be repeated every few years .

This level of performance is alreadyattainable, but the cost to the end-usercan be extremely high when usingcurrent survey practices.

The Limitations of TraditionalTechniques Conventional sonar surveys involvededicated vessels deploying fragileinstrumentation such as sonar arrays andsubmersible survey vehicles, controlled byand attached to the survey ship.Operating such equipment requiressufficiently calm sea states and operationsmust be suspended if the weatherdeteriorates, leading to delays andadding to the already high overall cost.Operating close to shore, which a highproportion of surveys require, can also bedangerous, due to the lack ofmanoeuvring options available and thegreater risk of damaging expensivesurvey equipment on underwaterobstacles.

BATHYMETRICMAPPING

Accurate maps of sea-bottom topography likethis one are used formany offshoreapplications, includingnavigation, fishing andconstruction. They arecurrently generated byconducting expensiveshipborne echo-sounding campaigns

The Benefits of Space-BasedMonitoringBy using Synthetic Aperture Radar (SAR)images like those provided by ERS, asignificant improvement in the quality ofthe interpolation of depth valuesbetween survey tracks can be achieved.The incorporation of SAR imagery meansthat surveys can be completed morequickly, leading to significant costsavings. SAR data can also be used inregions such as estuaries, where surveyships could experience difficulties. Thesurveys can therefore be completed witha reduced level of risk to equipment andcrew.

ERS’s frequent revisiting cycle allows theregular updating of maps for areas wherethe bathymetry is prone to rapid change,such as shipping channels subject tostrong sediment deposition.

To ensure that data quality is sufficient tomeet customer needs, accuratepositioning of both the mother ship andthe various measuring instruments isnecessary, which requires the use of GPStechnology. In addition, accurateunderwater telemetry is needed to fixrelative positions between RemotelyOperated Vehicles (ROVs) and the mothership in order to accurately locatemeasurement points.

One possibility for reducing the costs oftraditional bathymetric mapping methodsis to increase the spacing between surveytracks. However, this requiresinterpolation between the remainingtracks, thereby reducing the accuracy ofthe final product.

An ERS SAR imageillustrating thebathymetric features ofan area off the Belgiancoast. The proposedroute of an oil pipeline issuperimposed on theimage

*Advisory and ResearchGroup on ObservationsSystems and Services

Examples of Space-BasedApplicationsThe Bathymetry Assessment System(BAS): An overviewThe Bathymetry Assessment System,provided by the Dutch companyARGOSS*, consists of a suite of numericalmodels which calculate a synthetic SARimage from a first-guess bathymetry. Thedifference between the synthetic imageand the actual image is minimised insuch a way as to generate an update ofthe bathymetry. This process is repeateduntil the depth values converge.

The principal models, as indicated in theaccompanying diagram (bottom left), are: • two-dimensional shallow-water

hydrodynamic equations to determine current perturbations generated by the bathymetry

• a current-profile model to determine how these perturbations propagate to the sea surface

• a wind-wave model to determine how the perturbed currents modify the sea-surface roughness

• a backscatter model to translate the surface modulations to a SAR image.

The system requires the following inputdata: • sonar sounding data along calibration

tracks to calibrate the system • tidal data related to the acquisition time

of the SAR image • wind speed and direction related to the

acquisition time of the SAR image • SAR Precision Imagery (PRI) of the area.

Bathymetric Imaging withERS SARVariations in water depth perturb tide-generated currents, and theseperturbations can propagate upwards tomodulate the pattern of sea-surfaceroughness. If the wind speed is between3 and 9 m/s and the magnitude of thetidal current is sufficiently large (greaterthan 0.5 m/s), then these surfacemodulations can affect the backscatterobserved in SAR images of the region,allowing the observation of certainbathymetric features. The characteristicbackscatter intensity pattern associatedwith such surface perturbations isillustrated in the accompanying figure(above) .

To retrieve water-depth values, the SARinformation must be further analysed,which requires accurate models of thelocal hydrodynamics and wave evolutionas well as information regarding theprevailing environmental conditions, suchas wind speed.

The BAS package is very flexible in termsof hardware requirements and can be runeither on a PC under Windows NT or ona standard UNIX platform. An image-processing package is required togeolocate and transform the SAR data tothe local projection coordinates.

Using standard tidal and meteorologicaldata in the numerical models, theBathymetry Assessment System producesa chart with an r.m.s. depth accuracy ofbetween 20 and 30 cm. This iscomparable with traditional methods ofdepth echo-sounding, and substantiallymore accurate than data available fromstandard Admiralty charts. In addition tomeasurement accuracy, end users areinterested in location accuracy ofmeasurements. Using a georeferencingtechnique implemented by the TNO-FELInstitute in The Netherlands, each pixelwithin the SAR image can be locatedwith an accuracy of better than 30 m.The BAS-provided product is thereforecomparable in accuracy withconventional survey data, but is availableat a fraction of the cost.

Mapping the Plaatgat ChannelThe Plaatgat channel lies betweenthe Dutch islands of Ameland andSchiermonnikoog in the Wadden Sea areaoff the Northern Netherlands coast. Itconstitutes the main shipping routebetween the North Sea and the harbourof Lauwersoog. Owing to naturalsedimentation and erosion processes, thischannel moves eastwards and siltsregularly. At the same time, theneighbouring channel of Westgat getsdeeper. In view of the morphologicaldynamics of the area, Rijkswaterstaat(responsible for managing waterresources in the Netherlands) has decidedto survey the bottom topography of thearea every three months.

A demonstration project has beenundertaken using the BathymetryAssessment System, based on theassimilation of ERS SAR imagery. The SARimage of the Plaatgat channel shown

was then calculated and subtracted fromeach pixel, leaving a matrix of intensityvariations.

Tidal phase data were used to calculatethe displacement of the sea surface fromthe reference value, and hence thesurface current vectors within areas ofinterest. Finally, echo-soundings madealong a number of tracks wereassimilated into the system. Althoughsurvey tracks were spaced at a nominaloffset of 200 m for the purposes of thedemonstration, the ERS SAR data wereassimilated using a spacing of 600 m inorder to illustrate the utility of the BAS.The remainder of the data were used toevaluate the system’s performance.

here (above) was acquired on 3 August1995. As a first step, the image was geo-registered. Land features were identifiedand masked out and an “average”backscatter intensity for the entire image

The area of interest was split into tworegions, each corresponding to a reduced case of the two-dimensionalhydrodynamic flow equations, allowing afaster inferral of the water depth. A mapof data points was produced for the area(right), with a spacing corresponding tothe pixel spacing within the SAR image(i.e. 12.5 m). The accuracy of the depthestimates calculated by the BAS packagewas compared with the depth estimatesobtained from the conventional surveywith a track spacing of the order of 200 m (below right). The error within thearea surveyed was found to lie within the30 cm upper limit required by the enduser.

way, it will become a potential source ofinformation for all coastal engineers,harbour authorities, etc. who are requiredto integrate information from differentsources to ensure effective decisionmaking. In addition, the rise in demandfor digital charts is creating a furthergrowth market for BAS applications.

A further stimulus to the operational useof SAR information for bathymetricapplications will be provided by thelaunch at the end of 1999 of ESA’sEnvisat mission.

AcknowledgementsMuch of the information presented herewas supplied by ARGOSS. Theircontribution and the support ofRijkswaterstaat, the UK HydrographicOffice and Horizon Exploration, whosupplied images and illustrations, aregratefully acknowledged.

Contact AddressesFor further information on projectsreferred to in this fact sheet:

G.J. WensinkARGOSSPO Box 618325 ZH VollenhoveThe Netherlands

Tel: (31) 527 242299Fax: (31) 527 242016e-mail: [email protected]: http://www.argoss.nl

Cost/Benefit ConsiderationsThe following comparison is based on1995-estimated survey prices, comparingthe costs of traditional survey methodswith the BAS approach for an area of 300km2 and a survey track spacing of 200 m:

Traditional Methodology (excl. breakdown and weather-delay costs)

Total survey line 1500 kmAverage survey speed 6 knotsTotal survey time ~135 daysCost per day ~US$ 5000Approximate total cos US$ 675 000

BAS MethodologyCost of SAR imagery ~US$ 60 000(acquisition, processing, reporting, etc.)Field surveys ~US$67 500Total survey time 13.5 days of operationApproximate total cost US$ 127 500

Future OutlookThe Bathymetry Assessment System hasnow been implemented within theRijkswaterstaat Survey Department as afirst step towards the routine monitoringof Dutch coastal waters. Further testingof the system is planned and currentwork centres on the development of anoperational two-dimensional assimilationscheme to allow complex bathymetricgeometries to be measured moreprecisely.

In the longer term, the incorporation ofBAS output into standard GeographicInformation Systems is envisaged. In this










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WIND & WAVEFORECASTING

A fishing trawler in highseas. Precise wind andwave information areessential for these kindsof operations

The Need for BetterInformationIn many areas of marine activity,including the domains of ship navigationand routing, deep-sea fishing, oil and gasexploration, etc., the availability of timelywind and wave forecasting can be crucialto safe and economic operation.

With global reserves of oil and gasforever diminishing and demandincreasing, exploration companies arelooking to frontier areas offshore toprovide new and viable sources ofhydrocarbons. The wind and waveforecasting is often sketchy to say theleast in such areas due to the lack ofreliable meteorological data.Unanticipated downtime during seismicsurveys to pinpoint sites for exploratorydrilling can result in considerable financialloss.

When a rig is deployed at a newlydiscovered reserve, it is essential to beaware of any imminent extremeconditions such as unusually large swellwaves, etc., which can result indangerous resonant motions. Many ofthe associated operations such as cranelifts, tanker loading and drilling, involvethe coupling of structures or unevenlydistributed weightings. Excessive wave-induced motion can easily cause collisionsand capsizes. During pipeline-layingoperations, for example, which can onlybe carried out when there will be wavesno higher than 3 m for at least 6 hours,the costly crane lifts needed are totally atthe mercy of the elements.

All types of ocean vessels are vulnerableto wave-induced damage. There issignificant growth in both the size andnumber of ships navigating key routesacross the North Atlantic, around thePacific Rim and in the Persian Gulf.Currently, an average of three ships withdisplacements of over 500 tons are sunkevery week. The dry-dock refit costs forrepairing wave-induced slamming fatiguein those that survive such incidents canbe enormous.

As coastal fish stocks become furtherdepleted due to pollution and over-fishing, the fishing industry too is havingto move into more inaccessible andhostile waters.

WIND & WAVEFORECASTING

Crane heavy-liftingactivities around anoffshore oil rig

dedicated buoy networks, large parts ofthe oceans remain unobserved, includingkey frontier areas where marine activitiesare experiencing rapid development.

Today’s wind and wave informationrequirements are also rather diverse,depending on the specific application.Sometimes a “point-to-point” forecastalong a particular ship route may beneeded for a specific time period; inother cases regular forecasts are requiredwith a precise frequency of updating.

The Benefits of Space-BasedMonitoringClear benefits in the domains of marinewind and sea-state forecasting areobtainable through the use of theinformation collected from modern andsophisticated space instrumentation suchas that carried by the European RemoteSensing Satellites (ERS). Homogeneous,global and continuous coverage as wellas an improved resolution are some ofthe advantages over conventionalobservations from ships and buoys thatactive microwave sensors operating fromspace (i.e. ERS’s Altimeter, Scatterometerand Synthetic Aperture Radar (SAR)) canprovide.

Limitations of TraditionalTechniquesForecasts of marine wind conditions aretraditionally provided by nationalmeteorological agencies. Atmosphericmodels are usually driven by the few in-situ measurements available, which aregathered either by ships navigating alongmajor routes or by dedicated networks ofbuoys. Consequently, these atmosphericmodels may well not accurately representatmospheric cyclonic featurescharacteristic of storms that have notbeen measured directly. In order togenerate accurate wave forecasts, precisewind information is needed. As acomplement to the wave models used forthe sea-state forecasting, reliableinformation on wave height, period anddirection is required if the wave fields areto be accurately represented.

Expensive buoy network systems arecommonly used in areas with dense shiptraffic, such as Europe’s northwest shelf,to measure both winds and wave heightswith the spatial and temporal samplingneeded for modelling. Besides their highcost (over 1.5 million ECU per annum fora ten-buoy network), such networkssuffer from incompatibilities (i.e. themeasurements are not standardised) thatprevent neighbouring countries fromsharing the data, seriously limiting thesystem’s usefulness. Even with these

Surface wind vectors(dark arrows) andsurface pressuresaround tropical cycloneOliver, derived fromERS-1 Scatterometerdata and from ECMWFdata at 12 UTC on 11 February 1993. The cyclone waslocated in the SouthernPacific, where in-situobservations are sparse.The improvement withERS data in describingsuch features is self-evident

The Contribution of ERSOwing to the high revisit frequency ofERS, the global wind fields derived fromits Scatterometer are likely to allow thedetection of at least three or four of theten or so major cyclonic depressionsaffecting the Earth’s surface at any giventime, thereby improving both theatmospheric and resultant wave-fieldforecasts.

Wave-height observations provided byERS’s Altimeter, and measurements of theperiod of swells generated by evendistant storms thousands of kilometresaway, can be used to substantiallyimprove local wave forecasting. The highquality and reliability of ERS’s dataproducts, which have been thoroughlyvalidated, are important factors whenaccurate metocean and sea-state forecaststhat provide a true representation ofanticipated wind/wave fields have to begenerated.

Examples of Space-BasedApplicationsImproving meteorological forecastsIn various studies by the UKMeteorological Office (UKMO) and theEuropean Centre for Medium-RangeWeather Forecasts (ECMWF), assimilationof Scatterometer data was observed toproduce a marked improvement inmeteorological forecasts. Weatherforecasting reliability measures showedan improvement of 6-10% in surfacepressure fields and 2-4% in temperatureand wind-fields in the four-day forecastcompared with the global models derivedwithout the Scatterometer data.

Producing wave forecasts Every wave forecast is produced using aninitial state obtained by assimilating(blending) wind and wave data into anumerical model. The data are usuallygathered into six-hour windows centredaround the assimilation times. At eachtime increment, sea spectra arecalculated, using an action balanceequation where the evolution of theenergy spectrum of the waves is drivenby three contributory effects: energyinput from wind forcing (produced by anatmospheric model), nonlinear wave-wave interaction which transfers energybetween long and shorter wavelengthwaves, and energy dissipation frombreaking waves. The wave-model outputis then corrected locally withmeasurements of wave height using anoptimal interpolation scheme.

Wind measurements made by ships and satellites. Above: Ship in-situ wind measurements for the three-day period 31 October - 3 November 1990, each dot representing one wind-speed/direction report. Below: One day of ERS-1 Wind Scatterometermeasurements in March 1992

Impact of the inclusionof Scatterometer wind-field data on wave-forecasting accuracy.The output from a wavemodel when usingScatterometer windfields and wind vectorsderived from the Meteo-France operationalweather model wascompared with windvectors from driftingbuoys and Altimeterwave heights. The errorcurves obtained indicatea clear improvementdue to the inclusion ofthe Scatterometer input

The availability of global high-qualitywind- and wave-field data in near-real-time from ERS means that a suitablescheme is needed for assimilating thisvery large volume of data within the lifecycle of the operational forecast. Incontrast to conventional observingsystems which provide wind and wavedata at fixed times and locations, satellitedata are generated continuously atvariable locations, requiring a four-dimensional (both space- and time-dependent) assimilation technique andthe assignment of weightings to thevarious types of data. ERS Scatterometerdata are already being used to correctthe wind- field inputs for the atmosphericmodels of several meteorological officesaround the World, and the accuracy ofwave forecasts has been greatlyincreased.

Correcting wave fields with ERS waveheightsThe slope of the increase in the SARbackscatter signal from 10% to 90% offull energy correlates with the roughnessof the sea as measured by the satellite.It can therefore be used as a tool forsignificant-wave-height measurement.

Altimeter and Scatterometer data areassimilated into the ECMWF’s wave model(WAM) in order to produce its wind andwave forecasts.

Satellite data must be carefully cross-calibrated against in-situ wave-buoy andweather-station measurements

Operational use of ERS dataSince 1992, a number of customers,predominantly shipping operators andoffshore oil-production companies, haveavailed themselves of information derivedfrom ERS in the form of products tailoredto their needs and regularly provided bythe UK Meteorological Office (UKMO).

Scatterometer, Altimeter and SAR Wave-Mode data are incorporated into thegeneral forecasting products such as thefive-day ocean weather forecast. Thesedata are assimilated into numericalmodels which provide initial analysisfields of wind and wave data, uponwhich the forecasts are subsequentlybased.

Differences betweenwave-height outputsfrom the WAve Model(WAM) derived usingsimulated wind fields(no Scatterometer dataused), and themeasured significantwave height from theERS-1 Altimeter for July1993. This chartillustrates the magnitudeof the correctionsneeded. The new wavefield produced withAltimeter data includedwas validated withwave-buoy data; areduction in standarddeviation of 3% in theWestern Atlantic,increasing to 15% in theEastern Pacific wherethere are fewer in-situobservations, isapparent

Calibration of ERS-2wave heights with in-situmeasurements. Acomparison with buoydata for the period June1995 to August 1996shows that ERS-2underpredicts waveheights by about 8%,which is easily correctedfor before assimilation ofthese data

For the oil industry, the model outputsare extrapolated to the shallow watersaround the UK to provide operationalsupport in the planning and execution of such tasks as drilling and liftingoperations.

A third customer area is the coastalprotection and engineering industry,where users are supplied with dataextrapolated from the nearest grid pointto the location of interest via a transformincorporating the local coastalbathymetry. Companies operating in thisdomain, such as Delft Hydraulics and HRWallingford, buy such products from theUKMO in order to provide sea-defencedesign services to local authorities.

The “Neptune” service operated by theFrench national weather service Meteo-France is based on its own numericalwave forecasts and those from theECMWF, both of which incorporate ERSAltimeter and Scatterometer data. TheMeteo-France forecast is generated usingits own model of the atmosphere,ARPEGE, which ingests data from shipsand buoys and infrared satellite data. ERSScatterometer data are used to correctthe wind fields.

In addition to its general marine forecastproducts, the UKMO provides specificsupport for ship routing, with around1000 such contracts serviced annuallyand with 30-40 customers at any onetime. The modelling predictions areanalysed by experienced master marinersand the optimal routes recommended tothe ships’ masters.

Northeast Atlantic waveswell (left) and pressureand wind (right)forecasts provided aspart of the “Neptune”service

The data are transmitted via the Inmarsat-Csatellite to an onboard desktop computerequipped with the appropriateinterpretation software. The informationcan be viewed either in the form of achart, or in a user-defined format if theextraction of particular information, suchas waves exceeding a particular height, isrequired.

Depending on the customer’s particularrequirements, the “Neptune” serviceprovides pressure, wind speed anddirection, swell height, direction andperiod, and sea-surface temperatureanalyses. Forecasts are provided with aspatial resolution of 0.5 deg longitude fora five-day period. A chart of fronts andisobars containing both an analysis of thecurrent situation and a forecast for thefollowing three-day period is provided.

The “Neptune” service also allowsmariners to receive forecasts for a specificsea area, for example for delicate offshoreoperations (test drilling, pipelinedeployment) or for fishing purposes. Itcan also provide ship operators or yacht

racers with “point-to-point” forecasts innear-real-time during the course of avoyage.

Offshore-operations supportOffshore heavy-lifting operations can onlybe carried out if wave heights remainreasonably low for the duration of theoperation. In addition, the period of theswell must be sufficiently different fromthe natural periods of oscillation of thevessels involved.

Correct decisions about the suspension ofwork, for example if the risks to man andequipment are becoming too high, canonly be taken if accurate short- andmedium-term wave forecasts areavailable, particularly for the directionalwave spectra at the site of the operation.This is only feasible if both the temporalresolution and quality of the forecast aresufficient.

As a demonstration of the operationalapplicability of space-gatheredinformation, sea-state forecasts based onsatellite data were provided to the Dutch

wave and wind fields (from the UKMO)for the PHIDIAS numerical sea-stateforecasting model covering the North Seaand the Northeast Atlantic. An improvedforecast was thereby generated, whichwas validated using waverider anddirectional wave-buoy measurements. Theassimilation of ERS significant-wave-heightdata was found to be particularly usefulin the presence of strong swells.

The forecast contained information onsignificant wave height, period, wavelength and direction, as well as winddirection and strength. In addition,longer term forecasts on approachingswells were provided. These data werethen used to compute parameters suchas crane tip motions for lifting operations,to prevent pronounced tension variationswithin the lifting equipment anddangerous impact forces between theobjects being lifted and the other vessels.In one particular case, the improvedforecast predicted a peak in crane-tipmotions which was missed by the “first-guess” fields which did not include ERSdata.

offshore-engineering company HeeremacEngineering Services for a DelftHydraulics and Netherlands RemoteSensing Board project involving heavylifting and exploratory drilling operations.ERS-1 Altimeter and Scatterometerproducts were used to correct “first-guess”

Effect of the assimilation of ERS Altimeter data on wave prediction: the forecastprovided matched the reality very well

The further development of the waveforecasting system is currently beingcarried out by ARGOSS (Advisory andResearch Group on Geo-ObservationsSystems and Services) and is aimed atproviding fully operational systems andservices. To reduce the risk of damage tovessels and platforms etc. under tow, anonboard decision support system is alsounder development that includes bothtraditional onboard measurements andsatellite data

Cost/Benefit ConsiderationsThe scale and immediacy of the risksfacing industries which depend on thesea creates enormous potential for theapplication of accurate meteorologicaland sea-state forecasts. However, like allprivate-sector industry, these customersare extremely cost- and service-sensitiveand will only invest in the necessaryinfrastructure if the data products beingprovided meet their needs in terms ofaccuracy, reliability, timeliness and cost.

Where satellite data really comes into itsown as a source of information is infrontier regions for offshore operationssuch as the North Western Approachesor Southeast Asia, or for fishing activitiesin the Southern Oceans. In areas wherethere are insufficient in-situ measure-ments being made, ERS-2 data are anessential element for the production ofaccurate wind and wave forecasts.

Accurate wave forecasts are crucial forthe avoidance of extreme wave heightsand certain dangerous wave periodswhen planning so many critical marineoperations. The true benefits from theavailability of such services are still hardto quantify, however, as dangerousconditions do not occur during everyoperation. They are therefore often notfully accounted for in cost-benefitanalyses. Nevertheless, the human safetyaspect alone provides a substantialjustification for the economic investment,and the tangible financial cost-savingbenefits of using wave-forecastingservices are comparatively easy to assess.

Crane barge hoisting drilling andaccommodation facilities into place

Contact AddressesFor further information on projects referred to in this fact-sheet:

J.S. Hopkins UK Meteorological Office London Road Bracknell Berkshire RG12 2SZ (UK) Tel.: (44) 1344 856684 Fax.: (44) 1344 854906

J. Poitevin Meteo-France 42 avenue Gustave Coriolis 31057 Toulouse CedexFrance Tel: (33) 5 61 07 80 80 Fax: (33) 5 61 07 80 09

H. Wensink ARGOSS PO Box 61 8325 ZH VollenhoveThe NetherlandsTel: (31) 527 242299 Fax: (31) 527 242016

P. Janssen European Centre for Medium-RangeWeather Forecasts (ECMWF)Shinfield Park Reading Berkshire RG2 9AXUnited KingdomTel.: (44) 118 9499116 Fax.: (44) 118 9868450

Future OutlookThe efficiency of the assimilation of thesatellite-provided data is improvingsteadily. The European Centre forMedium-Range Weather Forecasts(ECMWF), which produces wave forecastsbased on the assimilation of ERS datausing the WAM model, has improved theoutput resolution of its global model from1.5 to 0.5 deg by means of technicaladvances within the system. This newresolution extends the wave forecastsfrom the open ocean to the coastal regionswithout the limitations of regional models.

Currently, ERS-2 satellite data is the onlysource of wide-area wave information innear-real-time. ESA’s next generation ofEarth-observing satellite Envisat, to belaunched in 1999, will have the ability tomeasure wave height, period anddirection using advanced versions of theERS SAR and Radar Altimeter sensors. TheScatterometer measurements presentlybeing made by ERS-2 will be continuedby the ASCAT instrument to be flown onthe METOP spacecraft due for launch in2001 for Eumetsat.

AcknowledgementsThe assistance of the followingorganisations in providing material isgratefully acknowledged: Shell UKExploration & Production, EuropeanCentre for Medium-Range WeatherForecasts (ECMWF), Jet PropulsionLaboratory, Meteo-France, ARGOSS,Heeremac Engineering Services, UKOffshore Operators Association.










><Prepared by:Remote Sensing Exploitation DivisionESRIN

MARINECLIMATOLOGY

The magnitude of theforces at work on theBrent Charlie rig duringa storm. Severedamage can be causedto offshore structures ifmarine climateinformation is notadequately consideredin their design

The Need for BetterInformation A wide range of users take advantage ofthe information contained in charts suchas those on the front page of this folder.They are just one example of the kind ofservices provided for many locationsaround the World by specialisedcompanies which produce estimates ofwave height and wind-speed climatologyfrom satellite data.

Climatological information is importantfor marine activities and operatorsworldwide. Recent research conductedby the Southampton OceanographyCentre (UK), for example, has shown thataverage wave heights over much of theNortheast Atlantic have increasedconsiderably in the past decades. In areaswhere marine activities are increasing,such as Southeast Asia and the east coastof South America, the need to improveon today’s sparse knowledge ofclimatological conditions is critical.

In such activities as offshore oilexploration (ship surveys, exploratorydrilling) and production (pipeline laying,jacket installation), bulk cargo shippingand trans-ocean towing, the largestforces suffered by the ocean-going vesselsinvolved are the result of wave activity.Knowledge of prevailing environmentalconditions is therefore crucial for sounddecision-making regarding the type ofvessel to be assigned to a specificoperation and the manner in which thatoperation is to be carried out. This isparticularly important when there are

likely to be extreme weather conditions,for instance during the winter months orduring the monsoon season.

Marine warranty companies also rely onclimatology information for a particularoperating area when they have to certifyoffshore structures and vessels foroperation. Certification involves ensuringthat a vessel is capable of operatingsafely under any conditions likely to beencountered, both nominal and extreme,and in compliance with local/national

MARINECLIMATOLOGY

The spread in designcriteria for offshorestructures caused bylack of reliableclimatological data,which means that largemargins must beincorporated

The Limitations of TraditionalTechniquesIn order to derive information about theclimatology of a particular marine area, astatistical analysis is performed on a longtime series of data on wave height,period, and direction, as well as windspeed and direction. Using these data,the climate of the area can be derived interms of the statistical likelihood ofencountering winds and waves of aparticular size, direction or period on amonthly or seasonal basis. Also derivedare the properties of the average waveexpected at a particular time of the year,and the maximum wave recorded in a 50or 100 year period. The longer the timeseries of observations, the moreconfidence engineers can place in thepredicted climatology.

regulations. The statistical criteria appliedusually include the highest wave heightsto be expected over a period of 100years, over a one-year period, or for theduration of the operation.

Being able to rely on precise marineclimatology information in new frontierregions is vital to the oil and gasindustries, in order for them to plan allphases of their operations safely and costeffectively, including:• initial exploratory seismic surveys,

where a day lost can represent a financial loss of thousands of ECUs

• engineering and maintenance work ondrilling rigs and production platforms

• establishing design criteria for offshore installations, where costly over-engineering can be avoided if precise climatological information is available atan early stage.

Reliable and accurate climatologicalinformation brings directeconomic benefits as well asimproved safety and efficiency.Pipeline contractors, forexample, who have to ceaseoperations in bad conditions,cost in a percentage of down-time when they bid for fixed-price work. Overestimation ofanticipated down-time raisesthe bid price, whilst under-estimation reduces the profitmargin.

Average significant waveheight (left) and windspeed (right) in the northIndian Ocean duringJuly, derived from ERS-1, Geosat andTOPEX data obtainedbetween 1986 and1996. Careful calibrationof each of thesealtimeters against USNDBC buoys ensurestheir mutual accuracy

In some cases, it is possible to split theseas and the oceans into “climate-coherent” areas which have a particularprevailing climate in terms of winds andwaves, so that measurements at onelocation can be considered representativefor the whole area. How large theseareas are depends on their geographicallocation and their proximity to currentsand coastlines. However, in some areasthere can be great variations over just ahundred kilometres, putting into questionthe validity of the climatologicalinformation supplied to a customer if thewave measurements were not madeclose to the location of interest.

As with forecasts of sea state, untilrecently wave data used in the extractionof climatological information have beenlargely unavailable outside the majorshipping routes, where a ship’s masterwould stand on deck and estimate thesize of the waves. Subjective observationsgathered in this way make the quality ofthe data, and thus the quality of theclimatological information derived from it,difficult to assess. One means ofimprovement is the extended deploymentof wave-measuring buoys, but theirmeasurements are still highly localisedand they are expensive to operate.

Another major drawback of conventionaldata sets is that the measurements arehighly localised in time as well as space,and extrapolations for extended periodsor for extreme values can beunrepresentative. Moreover, waveclimatology information has traditionallybeen provided in atlases or maps for aspecific area, based on data from in-situobservations. Increasingly, information isrequired on frontier areas for which theseatlases have inadequate accuracy.

The Benefits of Space-BasedMonitoringThe principal advantage offered by asatellite system is the greatly improvedspatial and temporal coverage that itprovides. Space-based observationsinclude every ocean, with frequentrevisits (periodicity depending on theorbit configuration of the satellite),allowing global archives to be built up. Inaddition, the greater accuracy of the dataensures the reliability of the climatologicalinformation that is ultimately produced.

An example ofcalibration of ERSsignificant wave heightwith buoy data for theNorwegian Seaperformed by Oceanor,the Norwegianoceanographiccompany

In addition, a global atlas of ready-madeproducts can be generated and stored ona CD-ROM or floppy disk. The climatologycan be presented as histograms or scatterdiagrams to illustrate the distribution ofdifferent measured values, or as mapsand charts similar to traditional atlases.

The Contribution of ERS SAR A substantial contribution has beenprovided since 1991 by the radarinstrumentation onboard the EuropeanRemote Sensing (ERS) satellite series,specifically the Radar Altimeter, the WindScatterometer, and the Synthetic ApertureRadar (SAR). These instruments have beencontinuously providing not only wide-area wind speed and direction(Scatterometer) data, but also wave-height (Altimeter), period and direction(SAR) measurements, even over regionsnever previously explored.

Examples of Space-BasedApplicationsThe on-line climatology databaseWith other satellite missions operating inparallel with ERS, such as Geosat andTOPEX/Poseidon, a time series of ten yearsof significant-wave-height measurementshas now become available. Each of thethree altimeters onboard the abovemissions has its own bias, requiringcalibration with other data sets.

These data are sorted by geographicalarea for ease and speed of extraction,and stored as an on-line database, whichis regularly updated with new data.

Pre-defined areas of quasi-homogeneousclimate, for which CLIOSat provides climatologyinformation

The quality of the derived climatology isheavily dependent on the accuracy andreliability of the data, with an additionalreliance on the coherence of themeasurements, related to the length oftime series these data represent. Bothaverages and the extrapolation toextreme values can be valid only whenthe data are representative enough topoint to a consistent result.

CLIOSat - a PC-based wave atlas One example of the operational use ofsatellite-derived information is CLIOSat, aPC-based system developed in France byMeteoMer (a meteocean informationcompany) and the National MarineResearch Institute.

CLIOSat makes available worldwidemarine climatology information in theform of a floppy disk or CD-ROM with a“point-and-click” interface. Histograms forpre-defined areas of reasonablyhomogeneous climate are provided.

CLIOSat provides a number of differentdata products and two main presentationformats: histograms and scatter diagrams.The products are derived from an archiveand retrieval system which stores allexisting ERS Altimeter, Scatterometer andSAR Wave Mode data in processed form,and which is updated on a regular basis(daily in the case of ERS-2 altimetry).Climates have been elaborated using

measurements from Geosat, ERS-1 (ERS-2for updates) and TOPEX/Poseidon. All ofthese measurements have been calibratedand validated with in-situ measurements,including those from Meteomer wavebuoys.

A variety of parameters can be selectedfrom the CLIOSat data, including windspeed, wind direction, significant waveheight (Hs), wave period and direction.The user is provided with eitherhistograms of the distribution of thesewind/wave parameters or with extremalvalues of wave height. These values areonly indicative (pre-project information)but offer a first impression of the range ofestimated extreme Hs values that couldbe encountered within an area ofinterest.

Users can obtain similar basic statistics(except extreme Hs values) on an area ofinterest (specified location and size) for aparticular period (year, season, month,combination of months) within 48 hoursvia the CLIOSat on-line service, using thefully up-to-date satellite database. Todetermine the precise metoceanconditions (extreme Hs value, wavestatistics) at a specific location (e.g. anoffshore or coastal site), more involvedanalysis methods are necessary, such asthe combination of satellite data withstochastic and meteo-oceanic models.

Two sample products from CLIOSat: a histogram of the distribution of the wavedirection on an annual basis for an area in the Central Atlantic (above) and ahistogram of the wave heights for the same area on an annual basis (below)

Both the CLIOSat software and the on-line service have a wide customer basethat includes the major oil companiessuch as Total (France), Shell (USA), ELF-Aquitaine (France) and Chevron Oil(USA). The CLIOSat service has alsoprovided data for frontier areas such asSoutheast Asia and West Africa, as well asfor such shipping routes as Taranto -Istanbul.

WAVSAT - an operational serviceCompanies engaged in offshore designand operational planning work can takeadvantage of the marine climatologyinformation provided by WAVSAT, aservice set up in the United Kingdom bySatellite Observing Systems (SOS) to meetspecific user needs.

From the WAVSAT database, whichpresently holds over 10 Gbytes of datawith regular updatings from newmeasurements, estimates of wave heightas well as wind-speed climatology derivedfrom satellite altimeter data can beobtained. The combination of datastorage by geographical location andpermanent on-line access facilitatesinformation extraction by the usersaround the World. A wide range of otherstatistics are also readily available fromthe WAVSAT database.

A cumulative probabilitydistribution of waveheight during Januaryfor an area north of theFalklands (48-50°S, 54-60°W), one of arange of productssupplied to ShellInternational Explorationand Production. TheFalklands is a frontierregion where little dataexists apart fromsatellite measurements.The line drawn on thecumulative distributionplot is the fit to the data,estimated by maximumlikelihood; the point atwhich it intercepts thetop of the plot is the100-year return valuefor that month

Cost/Benefit ConsiderationsClimatology information is primarily ofuse in optimising the decision-makingprocess regarding the design of structuresfor, and the planning of operations inthe global marine environment. Althoughit is hard to separate the benefits ofmeteocean data from those deriving fromother information sources, it is clear thatan engineering design team requires aprecise and reliable source ofclimatological information if it is tofunction efficiently. Without it, anoffshore structure may be over-engineered or, far worse, may not besufficiently resilient to withstand thewinds and waves to which it willeventually be exposed.

Especially in new frontier areas, access tosatellite-derived climatology information isundoubtedly a cost-effective tool forcompanies involved in the design andsafe operation of engineering structures.In the long term, the benefits of avoidingmishaps and unnecessary financialoutlays by taking advantage of modernsatellite-derived information sources faroutweigh the cost of the informationitself.

The users of this service include suchpublic bodies as the French MarineHydrographic Service and the UKDefence Research Agency. Both provideoceanographic information to theirrespective navies and to other bodiessuch as the French Maritime InsuranceCouncil and the French PetroleumInstitute.

Future OutlookAs the reliability of all wave climatologyinformation increases with the time seriesof the measurements, continuity of datais important. In addition, as the climatesof some areas are clearly changing,regular updates for already reasonablywell-known areas are required, makingcontinuity of measurement all the moreimportant.

Contact AddressesFor further information on theservices covered in this fact sheet:

P. Lasnier MeteoMer Quartier Les Barestes R.N. 7 F-83480 Puget-sur-Argens, France Tel: +33 94 45 66 11 Fax: +33 94 45 68 23 e-mail: [email protected]

J. P. Stephens Satellite Observing Systems Ltd. 15 Church Street Godalming Surrey GU7 1EL, United Kingdom Tel: +44 1483 421213 Fax: +44 1483 428691 e-mail: [email protected]

The next generation of ESA Earth-observing satellite Envisat, carryingbesides other instruments a RadarAltimeter and a Synthetic Aperture Radar,will be launched in 1999. Until then,continuity is being assured by ERS-2, which is making observations ofwind fields and wave heights andspectra, and by the wave-heightmeasurements from the TOPEX/Poseidonaltimeter. The eventual availability ofwave heights also from TOPEX andGeosat follow-on missions will mean thatwe will be able to rely on a much greaterdensity of sampling measurements in thefuture, and thus on an improved qualityfor the end products.

AcknowledgementsThe illustrative material used here wasprovided by: Shell UK Exploration &Production, Shell International Exploration& Production, Oceanor, Meteomer, andSatellite Observing Systems Ltd. ESA gratefully acknowledges theircontributions.











SEA–ICE MONITORING

The Need for BetterInformationSea-ice information is required by a widespectrum of users involved in maritimeoperations at high latitudes. Greaterexploitation of Arctic offshore oil and gasreserves has led to a requirement notonly for accurate and timely icemonitoring, but also for reliable designinputs in terms of ice statistics for offshoreconstructions. Other users, specifically incoastal regions, include coast-guard andharbour authorities. Operationalinformation on sea-ice status is alsorequired by the fishing industry for suchareas as the Barents Sea and the regionaround Svalbard, and by merchantvessels crossing ice-infested regions in theBaltic or the Canadian, Alaskan andEuropean Arctic.

Ice-breakers play an essential role in ice-infested waters by keeping the Baltic-Seaports open in the winter months andchaperoning vessels not adapted to icyconditions. These services are oftenprovided free-of-charge, but sometimesalso on a fixed-price basis so thatoptimisation of the routings can directlybenefit both operators and customers.

The ice-monitoring requirements forsupporting each activity overlapconsiderably, but differ in detail. Theextent of the ice provides safety limits forthose concerned with avoiding icealtogether. Ice-strengthened vesselsrisking navigation within the ice packrequire information on the ice-agedistribution and on pack motion in orderto avoid high-pressure ridges and identifynavigable leads. The end-productrequired is therefore a service thatincorporates all available data andcombines it with expert analysis.

SEA–ICE MONITORING

Precise knowledge ofsea-ice conditions isvital when offshoreoperations at highlatitudes are involved

critical requirements such as strategicinformation prior to operations in ice-infested waters, multi-temporalinformation on ice-pack drift, and spatiallydetailed nowcasts and forecasts forcritical areas such as straits are not met bythese services.

Useful but sparse information is providedin the form of reports from vessels alreadyin the ice, and from ice-breakers andweather stations. Other data sourcesinclude airborne-radar surveys, but theseare expensive and still provide onlylimited coverage. Although the radarsensor itself may be insensitive to theprevailing weather conditions, the aircraftupon which it is flown can be groundedfor days or even weeks at a time byadverse weather.

The Benefits of Space-BasedMonitoringSatellite image data have proved to be ofmajor benefit for regional ice surveillance.Large-scale monitoring of sea ice isroutinely performed using Special SensorMicrowave Imager (SSM/I) data, whichhave a coarse spatial resolution of around50 km. These data are independent ofcloud cover and the whole Arctic regionis covered twice daily. The NOAAinfrared/optical Advanced Very HighResolution Radiometer (AVHRR) has ahigher ground resolution (1 km), butboth cloud cover and darkness imposeconstraints on its operation.

The Limitations of TraditionalTechniquesMany countries already maintain ice-monitoring and forecasting services,including China, Russia, the USA, theScandinavian countries, Canada and theBaltic States. These services are essentiallytactical in nature, providing informationon conditions for planning within currentoperations and for the optimal routing ofice-breakers. A typical forecast serviceconsists of daily regional (500 km2

coverage) surveys in the form of ice typeand concentration maps. However, many

Ice chart derived fromNOAA AVHRR imagery,illustrating the impact ofcloud cover (white areas)

The Contribution of ERS SARThe ERS Synthetic Aperture Radar (SAR)instrument provides imagery of the Earthup to a latitude of 84ºN. It maintains ahigh radiometric accuracy at 100 mspatial sampling, which constitutes theoptimal trade-off between imageproperties and data size. This resolution isalso comparable to the Side-LookingRadar (SLR) data obtainable from aircraft.For ice monitoring, therefore, the SARrepresents a vital bridge between coarse-resolution satellite data and airborneradar, allowing leads and other featuresimportant for successful navigation athigh latitudes to be resolved. It operatesperfectly in all weathers and is unaffectedby the long dark polar winter. Ingenerating daily ice maps of regions thatare typically 500 km by 500 km in extent,it can be useful to combine the SAR’sdetailed high-resolution informationoutput (delivered just 2-3 hours afteracquisition) with other data sets such asSSM/I and AVHRR, when available.

Since the ERS SAR is an active microwaveinstrument that measures the energybackscattered from the Earth’s surface,one can distinguish the different ice typesand map leads, polynyas, shear zones,land-fast ice, drifting ice and the location

of the ice edge in the ERS imageproducts now commonly used for iceapplications.

The SAR can accurately identify the stateand condition of sea ice from thecombination of the backscatter from theice, the nature of the surrounding ice,the texture and the shape of the floes.Any ambiguities arising in thisclassification process can be resolvedthrough the use of expert regionalknowledge and auxiliary data sets, suchas meteorological information, ship andshore observations, aircraft and othersatellite data.

In addition to allowing the classificationof ice type, the delineation of the iceedge, the accurate determination of iceconcentration and the identification ofleads, the frequent repeat coverageprovided with the ERS SAR facilitates thedetection and monitoring of icemovements and floes, enabling thetracking of pack-ice and ice at the edgeof the Marginal Ice Zone.

The radarbackscatteringproperties of ice varywith its age. Theresponse from the iceis related to bothsurface and volumescattering propertiessuch as roughness,presence of meltponds, frost flowersand salinity anddifferent snow/ice types

This figure illustrates the SAR’s ability to provide high-resolution information. TheSAR swath cuts across the Odden ice tongue apparent in the coincident SSM/Iice chart. This tongue consists of small first-year and multi-year floes and locallyformed grease and pancake ice. These ice types were classified from the SARimagery and documented with in-situ ship observations (see photographs) fromaround area B. Dark signatures (above both B and C) are due to grease ice, whilebrighter signatures (below and around C, around B) indicate pancake ice

pancake ice

grease ice

The Northern SeaRoute, opened towestern shipping in1991

Examples of Space-BasedApplicationsThe “Icewatch” Service: Mappingthe Northern Sea RouteThe Northern Sea Route is thenavigational route along the north coastof Russia from the Barents Sea in the west to the Bering Strait in the east (see below). Taking this route can reducethe transit time between Europe and thePacific by approximately 10 days.However, the prevailing ice conditions inthe region restrict sea transportation toice-class vessels, as well as requiring ice-breaker assistance throughout the year.In summer, vessels ply the whole route,whereas in winter it is mainly the western

part that is used to serve the ports on theYenisei River. In addition, companiesinvolved in the offshore oil explorationand production activities in areas such asthe Eastern Barents and Kara Seas requireinformation on ice conditions for facility(rigs, etc.) structural design and formonitoring purposes.

An extensive ice monitoring andforecasting service has been built up overthe past 50 years in Russia for theNorthern Sea Route in order to providethe ice-breakers with information.Recently, a first joint project in Earthobservation between the Russian SpaceAgency (RKA) and ESA known as

Ice map derived from an ERS SAR imageand the coincident ice chart from theRussian Ice Service derived from SSM/Iand NOAA AVHRR data. Note areasaffected by cloud in the chart

maps were sent by telefax to the Frenchpolar-research vessel “L’Astrolabe” duringher voyage through the NortheastPassage from Norway to Japan.

“Icewatch” has been initiated. Its aim is toimplement satellite monitoring of theNorthern Sea Route, relying on thecombined use of ESA ERS SAR, RKAOKEAN SLR, and other remote-sensingdata. A pre-operational service has beenset up that provides users with ERS SARimages via NIERSC, an organisation basedin St. Petersburg that includes theMurmansk Shipping Company, theDickson Operational Centre and severaloil companies among its members.Several customers have already placedorders for regular satellite data, andoperational use of this promisingapplication is expected to growconsiderably, helped by the EuropeanUnion’s taking an interest in “Icewatch”.

The use of ERS-1 SAR data for near-real-time ice mapping in the Northern SeaRoute was demonstrated for the first timeby the Nansen Environmental andRemote Sensing Center (NERSC) inAugust 1991, just a few weeks after thesatellite’s launch. SAR-derived sea-ice

Other demonstrations have been carriedout by the Nansen Centers in Bergen andSt. Petersburg with several of the Russianice-breakers operating ice-convoy servicesalong the Siberian coast and rivers. A scientist from the Nansen Center in St. Petersburg travelled onboard the ice-breakers and analysed the SAR images inco-operation with the vessel’s captain andthe ice pilots.

The Inmarsat-A communications satellitehas been used to test new methods forthe near-real-time distribution of data toice-breakers operating in the NorthernSea Route. One of these experiments was performed on 25/26 January 1996,when the ice-breaker “Taymir” wassailing from Dikson to Beliy Island (70-80º E) in 100% ice. Using a PC and a modem connected to the Inmarsatstation onboard the vessel, processedERS-1 SAR images were received just 5 hours after the satellite overpass. Inthese images it was possible to clearlydistinguish areas of rough ice andhummocks (brighter signatures) fromsmooth undeformed ice (darkersignatures), allowing the ice-breaker tochange course accordingly and selectboth a faster and safer sailing route.

The UK Sea-Ice WorkstationexperimentIn the field of ice-charting, the mostcommon requirements that anoperational service has to meet are: • the production of precise and reliable

ice information derived from an efficient system capable of handling and merging heterogeneous data sets

• the dissemination of such information through optimal mechanisms tailored to user needs.

As an example of the efforts in thisdirection, a Sea-Ice Workstation has beendeveloped by Earth Observation SciencesLtd. (UK) with the support of the BritishNational Space Centre (BNSC) and theDefence Research Agency (DRA). The aimwas to prove the concept of usefullycombining different types of satellite data.Most of the processing was targeted atthe classification of ice into threecategories: open water, first-year ice andmulti-year ice. Contextual informationwas provided by data from the SSM/I andAVHRR sensors, but the detailed analysisof local areas was achieved using ERSSAR data.

The Sea-Ice Workstation was testedbetween 1994 and 1996 by supplyingproducts to operators engaged inoffshore activities in ice-infested waters.Charts were generated displaying ice-motion vectors, ice types, iceconcentrations and ice-edge locations,depending on the user’s requirements.The users to which the charts weresupplied, in digital form via Inmarsat or

SSM/I and NOAAAVHRR-derived icechart, with coincidentclassified SAR imagery

The Ice Prediction and AnalysisPlatform experiment An interesting experiment took place inAugust 1994, when Nuna Oil conducteda seismic survey in the ice-infestedGreenland Sea. Maps of local iceconcentrations and movements derivedfrom ERS SAR images were delivered innear-real-time by fax to the vessel carryingout the survey, by GEC-Marconi ResearchCentre (UK). The Canarctic ShippingCompany was also involved in theexperiment and had the task ofevaluating the satellite products from anoperational-user point of view.

Orbcomm receivers, included: an oilproduction platform operating in the Barents Sea; meteorologicalorganisations, for inputting intoforecasting models; and shippingoperators for route planning. A RoyalNavy submarine also received coded icecharts on a regular basis whilstsubmerged beneath the ice.

The result of these tests, a “ready-for-use”tool for ice pilots, is presently beingtested by weather-service authorities likethe VNN in Norway as a basis formodelling the movement of vesselsthrough sea ice.

Typical ice-edgeproduct from the IcePrediction and AnalysisPlatform (IPAP)experiment. The area tothe west in the imageconsists of first-year icewith a fringing of greaseice. The image isoverlaid by two edgelines, one generatedfrom the displayedimage, and one fromthe next overpass ofthe satellite three dayslater

Typical ice-concentration chartsoutput as part of theIPAP experiment. Theseice-concentration (andice-motion) maps werefaxed to the master ofthe ship via the Inmarsatcommunications satellitewithin 3 hours of thesatellite overpass. Thisallowed sufficient timeto revise operationaldecisions regarding thesurvey route and thedeployment of thehydrophone arrays

The ERS-1 SAR images were received atthe West Freugh ground station inScotland and transmitted viaconventional land lines to the GEC-Marconi Research Centre, where theywere processed automatically on adedicated system, the “Ice Prediction andAnalysis Platform” (IPAP). Ice-concentration and ice-movement mapswere derived and all data were stored forfurther use as multi-temporal ice edgeand pack-ice motion products. Avalidation study of the supervisedclassification algorithms available withinIPAP using coincident in-situ informationfrom the Canadian ice-breaker “MV Arctic”showed an accuracy of better than 98%for the area around the Bent Horn oilterminal

Cost/Benefit ConsiderationsThe ice workstations generate accurateand timely ice information thatconstitutes an immediate and tangiblecontribution to the activities of thestandard ice-charting service. Whenoperations have to be undertaken forextended periods in ice-infested waters,knowledge on pack movement androutes through leads is crucial to speedup transfers and minimise fuelconsumption. It also allows one to avoidusing ice-breakers unnecessarily.

In the Baltic Sea, for example, where ice-breakers are used extensively to keepharbours open in winter, approximately4000 ships visit the 23 Finnish harboursalone, each spending an average of fourdays in ice-infested waters. The cost ofdelays in this traffic amounts to $200million per year, in addition to the coststo harbour authorities and relatedindustry.

Contact AddressesFor further information on projectsreferred to in this fact sheet:

O. Johannessen Nansen Environmental and RemoteSensing Center Edvard Griegsvei 3aN-5037 SolheimsvikenBergen, NorwayTel.: (47) 55 29 72 88Fax.: (47) 55 20 00 50 e-mail: [email protected]

L. BobylevNansen International Environmental andRemote Sensing CenterKorpusnaya Str. 18,197110 St. Petersburg, RussiaTel.: (7) 812 235 7493Fax.: (7) 812 230 7994e-mail: [email protected]

Future OutlookOperational ice services need continuityof information flow and this is nowensured by the presence in orbit of boththe ERS and Radarsat satellites. Inaddition, the flow of satellite data willincrease considerably in 1999 with thelaunch of Envisat, the new ESA missioncarrying among other instruments anadvanced SAR instrument operating in awide-swath mode, which will be ideal forregional ice monitoring.

Acknowledgements Illustrative material used here wasprovided by the US Ministry of theInterior Minerals Management Service,the Danish Meteorological Institute,Nansen Environmental and RemoteSensing Center, Rand McNally &Company, Earth Observation SciencesLtd., and the GEC-Marconi ResearchCentre. ESA gratefully acknowledges allof their contributions

N. McIntyreEarth Observation Sciences Ltd.Farnham Business ParkFarnham, SurreyUnited KingdomTel.: (44) 1252 721444Fax: (44) 1252 712552e-mail: [email protected]

R. CordeyGEC-Marconi Research CentreWest Hanningfield RoadGreat Baddow, ChelmsfordEssex CM2 8HN, United KingdomTel.: (44) 1245 473331Fax.: (44) 1245 475244e-mail: [email protected]











OFFSHORE OIL ANDGAS EXPLORATION

The Need for BetterInformationThe Earth’s dwindling reserves of naturalhydrocarbons are obliging oil and gascompanies to expand their activities toever more remote and inhospitable areasof the globe. Harsh environmental

conditions and the lack of any surveysupport infrastructure combine to makeconventional prospecting techniques -marine seismic surveying, gravity- andmagnetic-anomaly mapping and testdrilling - extremely expensive in thesenew frontier areas. These methods ofdata collection are also very labour-intensive. The future viability andprofitability of the oil and gas industry istherefore strongly intertwined with thesearch for ever more efficient prospectingand surveying techniques that areoperable on a global scale.

The Limitations of TraditionalTechniquesThe costs associated with theidentification of new sources of oil andgas using traditional means are immenseeven in relatively accessible areas such asthe North Sea and the NorthwesternAtlantic. Additional costs must be metwhen tackling the more remote areassuch as the Arctic Ocean and inSoutheast Asia where hazards such as icefloes or severe storms can causeexpensive delays. Today, however, thedeployment of the such expensivesurveying resources can be optimised bythe judicious application of remote-sensing data.

OFFSHORE OIL ANDGAS EXPLORATION

Seismic profiles like the one shown here relatedto an area of the North Sea, reveal anticlinestructures which may indicate the presence of oiltraps.

Gravity-anomalyvariations over thePorcupine Basin area inthe Atlantic as derivedfrom ERS-1 Altimeterdata. These data clearlyshow a majortranscurrent fault (whitedotted line) which wouldbe difficult to detect inconventional seismicdata

Instantaneousmeasurement of satelliteheight above the seasurface provided by theERS-1 and ERS-2Radar Altimeter

satellite position data obtained from aworldwide network of tracking stations.In addition, the effects of tides, currentsand bathymetry on the sea-surface heightare determined and removed. Theresulting mean sea-surface height is thenconverted into variations in the gravityfield.

The Benefits of Space-BasedMonitoringIn the oil-prospecting domain, gravity-anomaly measurements are importantindicators of the presence of potentiallyoil-bearing structures beneath the seasurface due to the characteristicperturbations induced in the gravity fieldby the different rock types. Thesevariations in the gravity field causevariations in the shape of the sea surface,which represents a surface of constantgravity. Thus by precisely measuring theshape of the sea surface it is possible,once unwanted effects such as currentfeatures have been removed, to extractgravity anomalies and detect thepresence of hydrocarbon trap structures.

Satellite-borne radar altimeters, incombination with orbit-tracking data,allow such precise measurements of thesea surface to be made. The globalocean-surface height can be determinedby combining this measurement with the

Gravity field over the Falkland Islands, in the South atlantic, derived from Altimetermeasurements. Approximately 200 000 sq. km of the offshore area includessedimentary basins with significant hydrocarbon potential.

The Contribution of ERSThe ERS spacecraft carry a suite ofmicrowave instruments capable ofproviding geophysical explorationcompanies with valuable and timelyinformation, allowing them to achieveconsiderable reductions in their surveycosts. The two main ERS instrumentsrelevant for hydrocarbon exploration arethe Synthetic Aperture Radar (SAR) andthe Radar Altimeter.

The SAR provides an image ofapproximately 100 km x 100 km with aspatial resolution in the order of 25 m. Itallows the detection of oil slicks on thesea surface originating through seepagefrom subsea hydrocarbon deposits,thereby permitting the identification ofpromising areas for more extensivesurveying.

The Radar Altimeter measures the heightof the satellite above the sea surface toan accuracy of approximately 10 cm,allowing the inferral of gravity anomaliesarising from subsea geological structureswith oil-bearing potential.

Examples of Space-BasedApplicationsMarine gravity maps (Gravsat)Marine gravity maps based on RadarAltimeter data are already beingproduced for certain areas of the globe,including the Gulf of Thailand, the Gulfof Mexico, the East China Sea, the Bay ofBengal, the Falkland Islands and thenorthern seas off the coast of Russia.They are being generated and madeavailable to a number of oil and gascompanies, as well as to the BritishGeological Survey, by Satellite ObservingSystems (SOS) Ltd. (UK). Themeasurements also incorporate Seasatand TOPEX/Poseidon data and therecently declassified Geosat archives.Once the gravity anomalies have beendetermined, the necessary geophysicalinterpretations are performed andfeatures of interest highlighted for thecustomer.

SAR image acquired over the Gulf of Mexico. The naturally occurring seepageslicks have a characteristic “dog-leg” appearance. This image is part of a data setacquired and analysed by the GOSAP Consortium* as part of a major initiative inthe USA to exploit satellite remotely sensed data in the oil exploration andproduction industry

* A cooperation between universities (e.g. Texas A&M), national researchinstitutions (e.g. NOAA) and the oil companies (e.g. Shell and Marathon Oil).

Although in principle such seepage-slickdetection is also feasible with opticalinstruments such as the SPOT HRV, inpractice the need for cloud-free imagingand observation-geometry constraintslead to the ERS SAR being identified asignificantly better tool for detecting andmapping such phenomena.

Subsea hydrocarbon-depositlocationSmall amounts of oil leak into the oceanfrom subsea deposits giving rise todetectable surface slicks which can serveas an indicator of the presence of oil-bearing structures. Until now, there hasbeen no generally available, low-costmethod for identifying these seepageclues. During times of low to moderatewind speeds, the ERS SAR cansystematically detect these slicks overlarge swaths of ocean, regardless of theprevailing cloud or lighting (day or night)conditions. The backscatter levelsdetected by the SAR depend on smallcapillary waves on the sea’s surface whichare smoothed out by the presence of oil,causing a decrease in the surfaceroughness and making the slick areasappear darker than the surroundingocean in the SAR imagery. Compared toother oceanic surface features, theseseepage-slicks often persist over time, sothat multiple SAR images acquiredmonths apart during low-wind conditionscan be extremely informative.

Offshore basinscreening usually takesa few weeks and costsless than 0.5 ECU perkm2. Oil companiesuse the service toselect/rank explorationblocks offered bygovernments and toprioritise theacquisition/purchase ofseismic data

The offshore basin screening serviceThis is a service offered to the offshoreoil-exploration industry, by Nigel PressAssociates and TREICoL in the UK, whichsaves time and money by prioritisingseismic expenditure and focusingattention on the most prospective basins.

Radar Altimeter data from ERS-1/2 arecombined with similar data from othermissions, resulting in a track spacing thatcan be as close as 1 km. Othergeophysical information is alsoincorporated where available. Thealtimetry is converted to a gravity mapthat can outline the basins in which oilmight be present. These gravity maps arecombined with a map of sea-surface slicksresulting from natural oil seepages, asdetected and analysed in SAR images.

Cost/Benefit ConsiderationsThe space-based services currentlyprovided to the oil-exploration industryare not intended to replace conventionaltechniques such as seismic mapping andship-borne gravity-anomaly studies. Theaccuracy possible with conventionalsurveying techniques is presently severaltimes better than is possible with satellitemeasurements given that the ground-track resolution for Altimeter-basedgravity-anomaly studies is still in theregion of 7 - 10 km. With ship-bornegravity-anomaly mapping, the trackspacing can be made as close as onewishes. The advantage of the satellite-based techniques is that the costs aremany times lower than with conventionalmethods, offering exploration companiesthe opportunity to perform a preliminaryanalysis of a region before committingexpensive resources to any survey. Inaddition, the satellite coverage provideseasy access to remote basins without theneed for an expensive supportinfrastructure.

Contact Addresses

For further information on projectsreferred to in this fact sheet:

Mr J.P. StephensSOS Ltd.15 Church StreetGodalming, SurreyUnited Kingdom

Tel: (44) 1483 421213Fax: (44) 1483 428691

Mr N. PressNPA Group Ltd.Edenbridge, KentUnited Kingdom

Tel: (44) 1732 865023Fax: (44) 1732 866521

Future OutlookAlthough there has been considerableinterest from the oil industry in theexploitation of remote-sensing data forseveral years, it is only now, with theavailability of the ERS data products, thatthe services provided to the industry arebeginning to meet its requirements interms of precision and coverage. Many oiland gas companies are already activelyusing ERS data in their day-to-dayactivities - including British Gas, Statoil,Exxon, Shell, Marathon, Mobil, Amoco,Pecten, and Chevron - and their numbercan be expected to grow substantially inthe coming years.

Together with the anticipated progressiveimprovement in terms of quality, theservices already available will benefit fromthe continuous provision of data that willbe ensured by the launch of ESA’s Envisatspacecraft at the end of 1999, carryingamong other instruments both anAdvanced SAR and a Radar Altimeter.

AcknowledgementsThe illustrative material presented herewas provided by: Fugro, the GOSAPConsortium, Grant-Norpac, IntegratedGeophysics Corporation Inc., theTechnical University of Delft, Shell TheNetherlands, Elf Enterprises CaledoniaLtd., Western Geophysical, Nigel PressAssociates, and Satellite ObservingSystems (SOS) Ltd. ESA gratefullyacknowledges all of their contributions.










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