The search for a settlement and buildings related to the grave mounds hadbeen fruitless until archaeologist Terje Gansum, head of the MidgardHistoric Center, decided to invest in a GPR survey to investigate atopographic low area just outside the boundary of the park. He speculatedthat a large house could have once been located at this site and that theelevation change is caused by a so-called house terrace.

The site is located in a flat field covered with shallow vegetation.Theweather had been dry and windy, resulting in good humidity contrasts inthe topsoil which contains relatively little clay. The survey was conductedusing a Noggin plus 500 MHz GPRsystem mounted on a SmartCart.Within an afternoon and thefollowing morning an areameasuring 100 m x 25 m wassurveyed at a 0.25 m line spacingwith 0.05 m trace spacing (stepsize) along 50 m profile lines.

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SSuubbssuurrffaaccee VViieewwssGPR technologyVol 5, No. 19 July 2009

EKKO_Mapper now has moremapping power. Depth slicesand cross-sections are easilydisplayed, with GPS and depth slicesexported to Google Earth!

Using the GFP_Edit utility program thataccompanies EKKO_Mapper V4, globalpositions in Latitude/Longitude or UTMcan be added to the GPR Grid (GFP)file. There are two ways to add GPS tothe grid data:

using GPS acquired during datacollection of the grid oradding global positions later.

GPS collected during GPR SurveyIf GPS data were acquired during theGPR grid survey (Figure 1 - page 2),GPS positions are added to each GPRline using the GFP_Edit program. TheGPS position of the grid is determinedby a best-fit calculation of the GPR gridlines to the GPS data (Figure 2 - page 2).

GFP_Edit displays both the GPR gridlines and the raw GPS lines to providea visualization of the accuracy of theGPS positions. "Whiskers" indicate theaccuracy of the GPS line compared to theGPR line (Figure 2 - page 2); the longerthe whisker, the poorer the GPS accuracy.

Many people are surprisedat the inaccuracy of their lowto moderately-priced GPS,despite the best-case claimsof GPS manufacturers. Thebest-fit calculation providesthe most accurate placementof the grid in global coordi-nates so even relatively poor

Viking Royalty in Norway

Sensors & Software Inc.

Noggin SmartCart reveals:

(continued on page2)

EKKO_Mapper V4 Software: New GPS features

In This IssueEKKO_Mapper V4 . . . . . . . . . . 1,2Viking Royalty in Norway . . . . . .1,3

See us at . . . . . . . . . . . . . . . . . . . 4Ask the Expert . . . . . . . . . . . . . 3,4

(continued on page3)

Noggin SmartCart surveying in the field just outside Borre park for a Viking longhouse.

The archaeological prospection unit of the Swedish National HeritageBoard recently conducted a GPR survey on behalf of the MidgardHistoric Center and Vestfold County administration in southernNorway. The Center is located next to Borre National Park, home to the Borremound cemetery and known for its exceptional collection of burialmounds dating to the early Viking age. Seven large andtwenty five smaller mounds and one cairn are foundin the area.

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SSuubbssuurrffaaccee VViieewwss Page 2July 2009Sensors & Software Inc.

Figure 1: Collectinga grid with GPS.

GPS data should provide reasonablepositioning of the grid.

Adding Global Coordinates inPost-PProcessingGlobal coordinates can be added to gridseven if simultaneous GPS was notcollected during data acquisition. If twoGPS positions in or near the grid areknown or one GPS position and theY-axis heading, the GPS locations for allthe lines in the grid can be calculated.

One way of getting global (GPS) coordi-nates is using Google Earth. If the gridlocation can be found on Google Earth,the Global position (in Latitude/Longitudeor UTM) can be extracted and enteredinto GFP_Edit (Figure 3).

Global coordinates may also be availablefrom government maps of the grid areaor from a hand-held GPS.

More Export OptionsEKKO_Mapper V4 also offers moreexporting options. When EKKO_Mapper V4opens a grid (GFP) file with added GPS,the GPS data are displayed on theStatus Bar as the mouse cursor is movedover the depth slices and cross-sections.The positions of targets in the depth sliceor cross section are saved to theclipboard by placing the mouse cursor onthem and then pressing the F8 key. Thismakes it very easy to paste significantpoints into an Excel spreadsheet, Worddocument or other files (Figure 4).

As well as exporting depth slice data toComma Separated Values (CSV) files,depth slices can now be exported toSurfer GRD files, 3D HDF data files andGoogle Earth KMZ files.

When depth slices are saved to a GoogleEarth KMZ file, Google Earth is auto-matically launched (if available) and"flies" to the location of the grid. Thedepth slice is superimposed over theground image (Figure 3). The user canselect slice images from different depths.

For more information about EKKO_Mapper V4or to request a trial version, contact us.

Figure 2: GFP_Editcalculates a "best-fit"ofthe raw GPS data to theGPR grid lines anddisplays the differencewith "whiskers".

EKKO_Mapper V4 (continued from page 1)

Figure 4: Positionalinformation of targets inthe GPR data are easilyexported to Excel andother file types.

Figure 3: Depth slice displayed in GoogleEarth. The GlobalPosition of a GPR gridcan be determined usingGoogle Earth

SSuubbssuurrffaaccee VViieewwssPage 3July 2009Sensors & Software Inc.

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Will the metal in my steel-toed bootsaffect my GPR data?

Small bits of metal around the GPRsystem, like the metal in yourboots or belt buckle, do nottypically affect the GPR data. In fact, theSmartCart used with our pulseEKKOPRO and Noggin products containsseveral metal parts including axles,screws and pins.

Ask-tthe-EExpert Longer metal wires and objects withlengths similar in length to the antennasmay in fact be a problem if they areparallel to the antennas or are close toor touching the antennas, transmitter orreceiver. In this case signals can leakfrom the GPR system onto the metalitem producing noise visible in theGPR data. Unshielded, low frequencyantennas are especially susceptible tonearby metal wires and cables.

The cabling associated with a GPSreceiver is a common problem. Thecable should have RF loading added, (continued onpage4)

Using a trace stacking factor of 4 and atime window of 99 ns, a total of 203profile sections (over 10 km) wererecorded under almost perfect surveyconditions.

When the data was processed and thefirst depth slices appeared on themonitor, the results were surprising.Below the diffuse reflection pattern ofthe approximately 35 cm thick ploughlayer, the clear anomalies caused by thepostholes of two early Viking age longhouses became visible. Between 50and 60 large anomalies (70cm - 120cmdiameter) indicate the former location oflarge wooden postholes which, duringthe early Viking age, formed twoimpressive longhouses. The outer rowsof postholes are bent like the sides of aboat while the inner rows of postholesindicate where the roof bearing postshad been located. These longhouseshave a length of about 40-50 m, were12 m wide in the centre and presumablyup to 13 m high. They are considered tohave been the precursors for theNorwegian wooden stave churches.

While the postholes appear as darkanomalies, we can see reflections ofstones deeper down in the postholes.Faint linear anomalies indicated outer

walls and subdivisionsin the hall buildings aswell as entrance areas.

The new discovery isthe most excitingViking-age find in thearea since a Vikingship was discoverednearby over 150 yearsago, and may rewriteViking history. Thelarge hall buildings arebelieved to havebelonged to a royalpower center at Borre,which has so far onlybeen known as acemetery.

Many exciting newdiscoveries are likelyto be made at this site,both with high-resolutionGPR measurementsand through targetedarchaeologicalexcavations.

Story and images courtesy ofImmo Trinks, Swedish NationalHeritage Board.

GPR depth-slice (60-70cm)

Viking Royalty in Norway (continued from page 1)

GPS cable noise visiblein the GPR data.

post-hole anomalies

Interpretation of the GPR data showing thetwo Viking age long houses and related post-holes, a modern pipe and vehicle tracks.

Artist's concept of the Viking longhouses

SSuubbssuurrffaaccee VViieewwss Page 4July 2009Sensors & Software Inc.

ss uu bb ss uu rr ff aa cc ee ii mm aa gg ii nn gg ss oo ll uu tt ii oo nn ssSensors & Software Inc.1040 Stacey Court Tel: (905) 624-8909 Email: sales@sensoft.caMississauga, ON L4W 2X8 Canada Fax: (905) 624-9365 Website: www.sensoft.ca

See us at ...

OSP EXPO 2009Minneapolis, MNSeptember 2 - 3, 2009http://www.ospmag.com/expo/

ICUEE 2009Louisville, KYOctober 6 - 8, 2009http://www.icuee.com/index.asp

GSA 2009Portland, OROctober 18 - 21, 2009http://www.geosociety.org/

ASNT Fall ConferenceColumbus, OHOctober 19 - 23, 2009http://www.asnt.org/

Technical Papers1. Joint time-frequency analysis of

GPR data over layered sequences,The Leading Edge - Special Section:Near-Surface Geophysics, November '08Issue, Page 1454 -1460By: S. Guha, S. Kruse, P. Wang2008 ref 386

2. A Comparison of ElectricalResistivity, Ground PenetratingRadar and Seismic RefractionResults at a River Terrace Site,Journal of Environmental & EngineeringGeophysics, Volume 13, Issue 4, pp. 325-333By: M. Hirsch, L.R. Bentley, P. Dietrich 2008 ref 388

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Ask-tthe-EExpert (continued from page 3)excess cable tightly coiled and be rundirectly from the GPS receiver to theDVL, making sure it does not drapenear the GPR electronics orantennas. The GPR power andodometer cables should also be keptaway from the GPR transmitter,receiver and antennas.

Noise from metal cables is whySensors & Software's innovation ofusing fibre optic cables for low fre-

quency data collection dramaticallyimproved data quality. Other GPRsystems relied on long metal cableswhich produced strong, unwantedartifacts in the data.

Higher frequency antennas (above200 MHz) are shielded so nearbymetal is less of an issue but it isalways good field practice to keepmetal as far away as possible.

pulseEKKO PROConquest

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ConquestViewNoggin SystemsOEM Nogginplus

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EKKO_MapperEKKO_View3 Day GPR Short Course1 Day Noggin Short Course1 Day Conquest

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Imaging Concrete with GPR workshopsOther (please specify)

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One Day Noggin Short Course

September 14, 2009November 2, 2009

Our Noggin short courses are offered throughout the

year to anyone interested in learning more about GPR

and subsurface imaging.

One Day Conquest Course

September 15, 2009November 3, 2009

Our Conquest courses are offered to anyone

interested in learning more about our concrete

imaging instrument.

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Imaging Concrete with GPR - September 29, 2009 - Mississauga, ON

- October 14, 2009 - Chicago, IL

Ability to survive the toughestand most extreme environments

A rigid yet flexible, more durablematerial for longer life

Improved module interconnectfor 25 and 12.5 MHz

Improved quick-release handleand support mechanics

NEW pulseEKKO dipole antennas