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HYDROGRAPHIC PERFORMANCE STANDARDS

HYDROGRAPHIC

PERFORMANCESTANDARDS

JUNE 2003

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TABLE OF CONTENTS

Page

Table of contents.........................................................................................................................2

What are standards? ....................................................................................................................3

Uncertainty management ............................................................................................................5

Summary.........................................................................................................................6

Expressing uncertainty ....................................................................................................7

The IHO S44 standards...............................................................................................................8

The US Army corps of engineers standards.................................................................................9

CHS Survey Standing Orders.................................................................................................... 10

NOS Specifications and deliverables.........................................................................................11

NOS Statement of Work ...........................................................................................................14

CLCS Guidelines......................................................................................................................15

NAVO hydrographic procedures............................................................................................... 16

LINZ provisional mulibeam specifications................................................................................ 17

DGPS Data format standards: RTCM SC-104.......................................................................... 18

DGPS Data format standards: NMEA 0183 ..............................................................................19

The standards of competence for hydrographic surveyors .........................................................20

The International organization for standards (ISO).................................................................... 21

International Marine Contractors Association (IMCA).............................................................. 22

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WHAT ARE STANDARDS?

The word standards implies something which can be used as a basis for comparison, such as amodel or a set of rules, or an authorized measure of some kind. Along these lines, theInternational Organization for Standards (ISO) defines the term standards as

Rules, guidelines, and definitions of characteristics, which ensure that materials,

products, processes and services are fit for their intended purposes.

Standards can have one of a number of objectives, and thus be labeled as a particular type ofstandard:

aproduct standardspecifies characteristics for a specific product (hydrographic example: theproduct specification for the Electronic Nautical chart, contained in IHO Special Publication S-57, version 3, Appendix B.1);

aperformance standardspecifies the functions which a particular product or service mustprovide (hydrographic example: the performance standard for Electronic Chart Display andInformation Systems (ECIDS), approved at the 19th biennial assembly of the InternationalMaritime Organization (IMO) in November 1995).

aprocedural standardspecifies the methods and procedures which must be rigorouslyfollowed to achieve a particular result (geomatics example: the survey standards required toachieve first order horizontal or vertical geodetic control). Generally speaking, proceduralstandards are rather inflexible, and are less in vogue now than they once were, and are graduallybeing replaced by performance standards.

a data standardspecifies the format and content of data. This may be very specific, such as theNational Marine Electronics Association (NMEA) 0183 Standard for interfacing marineelectronic devices. Or this may be generic, such as the ISO/IEC 8211 Specification for a datadescriptive file for information interchange, which provides a file-based mechanism for thetransfer of data of any kind from one computer system to another, independent of computer typeor operating system.

a quality standard, which most recently has implied generic management systems standardsfor ensuring the quality of products and services, commonly referred to as ISO 9000 family ofstandards. Many hydrographic organizations have adopted ISO 9000 quality management.

As indicated by these examples, there are a number of international, national, and enterprise(company) standards which prescribe acceptable and competent hydrographic practices andprocedures. We will not attempt a comprehensive review of all such standards during thiscourse. We will look at a few of the more important ones.

This course is about multibeam sonar data acquisition and processing. The relevant standards inthis case provide rules and guidelines for design and execution of a multibeam survey, and forthe assessment of the quality of the resulting information. Key quality factors in survey design

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are coverage and resolution each of which will be considered in later lectures. The keyquality factor in data assessment is uncertainty - what are the uncertainties in the resultingbathymetric, positioning, and sonar backscatter information, and how do these uncertaintiescompare with international standards and with end-use requirements?

In other words, the point of view from which we consider standards for this lecture is their rolein uncertainty management.

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UNCERTAINTY MANAGEMENT

Hydrographic information, whether from a multibeam survey or otherwise, is used to makeinformed decisions. Vessel navigation decisions. Resource management decisions. Coastaldevelopment decisions. Environmental management decisions.

The confidence with which such decisions can be made depends on the confidence which can beplaced on the hydrographic (and other) information available to assist in making informeddecisions. This confidence is usually expressed as a quantitative uncertainty. Other terms whichare sometimes used are accuracy, reliability, and errors, although the term uncertaintyseems to be a better, more generic, and neutral term than these alternatives.

The uncertainty associated with hydrographic measurements will affect both: (a) uncertainty inthe location of a hydrographic data point; and (b) the depth associated with a hydrographic datapoint. Hydrographic uncertainty can be calculated, represented and modeled in subsequent

calculations.

Uncertainty management involves both the design of a hydrographic system and the evaluationof results and products which are derived from hydrographic data.

Measurements are always uncertain, to some degree. Uncertainties are of three fundamentallydifferent types: accidental, systematic or random, and each type must be dealt with differently.

In this course, we use the term data cleaning to describe methods which are used to deal withaccidental uncertainties, (also called mistakes, blunders, or outliers).

In this course we use the terms artifact to describe systematic uncertainties (at least thosesystematic uncertainties for which we suspect a cause), and we refer to artifact detection and,if possible artifact removal as further steps in the data-cleaning process.

Once we have done our best in data cleaning and artifact removal, we are left with randomuncertainties, or noise, in the data. Sometimes it is appropriate and possible to reduce the noiselevel in our data by use of suitable filtering and smoothing of the data, but this requires caution.It is always a danger that such filtering will re-introduce systematic uncertainties, due to thefiltering process itself, rather than to the measurement process in which we are primarilyinterested.

In any case, when we have done our best, if we are fortunate, we will be left with some

remaining random uncertainties. If we are unfortunate, we will still have residual systematicuncertainties which we cannot remove. If we are really unfortunate, there may still be blundersor outliers which we cannot remove with certainty, because it is impossible to decide whetherthese data points represent real features, or are accidents of measurement.

To meet the requirements for informed decision making, mentioned above, we must be able todescribe these remaining uncertainties in some standard way. One variety of such an uncertaintydescription is precision which describes the consistency our data. Another variety of such an

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uncertainty description is accuracy, which in a perfect world indicates agreement of our datawith the truth (whatever that may be).

In either case, these descriptions of uncertainty are based on statistical principles and standards.The mean and the standard deviation are the two most common statistical descriptors ofmeasurement uncertainties. The mean is the average value of a series of measurements. If wesubtract the mean value (or perhaps a true value if such is known) from every measurement,we have a series of residuals or deviations from the mean. If we calculate the square-root ofthe sum of the squares of these residuals, we obtain the standard deviation for that measurementseries. When discussing measurements which have a number of dimensions or time-correlatedquantities (as we most certainly are for a multibeam survey), then these simple concepts can beextended into several dimensions by considering a mean vector and a covariance matrix inplace of the sample mean and standard deviation.

Data-sets of many measurements tend to have a special statistical character, known as a Gaussiandistribution (the familiar bell-shaped curve), provided all accidental and systematicuncertainties have been removed, so that the uncertainties are purely random. This Gaussiancharacter is an approximate model of reality, and becomes a better model the larger the numberof values which are being considered (something called the Central Limit Theorem).

But what does all this have to do with the confidence we can place in our information ormeasurements? It is another statistical principle that we can predict, under specific statisticalconditions, how often our measurement uncertainties (or more specifically our measurementresiduals) are likely to exceed a certain value. The value (or values) in question are referred to asthe confidence region, and the likelihood that our measurements lie inside this confidenceregion is referred to as the confidence level.

The international standard for confidence level is 95% in other words 19 times out of 20. 95%

is confidence level associated with weather predictions. 95% is the confidence level associatedwith election outcome predictions or public polling results. And 95% has become the standardfor expressing the confidence level for results derived from hydrographic measurements.

If data has a Gaussian distribution, the 95% confidence region is related to the standard deviation(in one dimension) or the covariance matrix (in several dimensions) by a simple scale factor.

SUMMARY

Hydrographic uncertainty management consists of the following steps:

Establishing what size confidence region is required for hydrographic measurements, in orderthat the hydrographic results upon which decisions of a particular type (e.g. following a safenavigation route) can be made with acceptable confidence.

Designing a measurement system (e.g. multibeam equipment, operating procedures, and datacleaning methods) which is intended to achieve this required confidence region.

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Assessing the confidence region actually achieved, after data cleaning, and comparing thiswith the required confidence region.

Presenting these uncertainties (or confidence regions) in an easily-understood way to thosewho will be making decisions based on hydrographic information.

Guidelines for the first step are embodied in the IHO S44 standard, and several alternativesstandards documents. Guidelines for the positioning part of the second step are embodied inRTCM and NMEA standards for DGPS. Uncertainty management specifically for multibeamsonar surveys are addressed by some of these documents as well. Analysis of the discrepanciesamong redundant data is the standard tool used for the third step. The fourth (presentation) stepis still in its infancy, represented by such objects as source diagrams on nautical charts, and thecatzoc attribute specified in IHO S57.

EXPRESSING UNCERTAINTY

In recognition of the growing international consensus on the evaluation and expression ofmeasurement uncertainty, the International Bureau for Weights and Measures (BIPM) conveneda Working Group on the Statement of Uncertainties, which in 1980 recommended thepreparation of what became theISO Guide to the Expression of Uncertainty in Measurement.This guide, commonly referred to as ISO GUM, was completed in 1995. A United Statesversion, which differs only using a dot rather than a comma as the decimal marker, and usesAmerican rather than British spelling, was completed in 1997. These efforts also contributed toa standardized vocabulary, which was captured in theISO International Vocabulary of Basic andGeneral Terms in Metrology, commonly known as ISO VIM, and published in 1993.

Complementary documents are available from several other sources, for example, the United

States National Institute of Standards and Technology website

The references mentioned are:

ISO VIM 1993, The International Vocabulary of Basic and General Terms in Metrology ($71)

ISO GUM 1995, The ISO Guide to the Expression of Uncertainty in Measurement, internationaledition ($92)

American National Standard for Expressing Uncertainty--U.S. Guide to the Expression ofUncertainty in Measurement, ANSI/NCSL Z540-2-1997 101 pages ($50)

Taylor, Barry N. and Chris E. Kuyatt (1994) Guidelines for evaluating and expressing theuncertainty of NIST measurement results. NIST technical note 1297.

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THE IHO S44 STANDARDS

The purpose of the International Hydrographic Organization Special Publication No. 44 (oftenreferred to IHO S44, or simply S44): IHO standards for hydrographic surveys is stated to be:

To specify minimum standards for hydrographic surveys in order thathydrographic data collected according to these standards is sufficiently accurate

and that the spatial uncertainty of data is adequately quantified to be safely usedby mariners (commercial, military or recreational) as primary users of this

information.

S44 was first published in the 1960s. The most recent edition, the Fourth Edition, waspublished in early 1998. S44-4th Ed marks a dramatic change in the content and approach takenby the IHO in setting standards.

To set the stage, S44 3rd

Ed was published in 1987, and, like the earlier editions, it specified asingle standard for hydrographic surveys. This single standard was based on the requirementsfor a nautical charting survey, the main concern of the IHO member organizations at that time. Itwas also based on the assumption that paper charts are the sole method of deliveringhydrographic information. The particular standards required for high density bathymetricsurveying methods were not considered, such as Lidar, multi-transducer boom-sweep, andparticularly multibeam swath systems. And finally, the S44 3rd Ed did not take into account theimpact of widely available Differential GPS positioning, both for hydrographers, and formariners using hydrographic products.

IHO policy has been to review and update publications like S44 on a five-year cycle. This

process began in 1992 for S44. However, mere updates and modifications were not consideredto adequately address the major changes occurring in hydrographic technology, and there wasmuch debate about what should and should not be included in the standards. Hence, preparationof S44 4th Ed took over five years to complete.

A copy of S44-4th

Ed is provided with this unit.

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THE US ARMY CORPS OF ENGINEERS STANDARDS

The US Army Corps of Engineers defines hydrographic surveying as follows:

Hydrographic surveying is performed to determine the subsurface topography (orbathymetry) of a site which affects the planning, acquisition, design, construction,operation, and maintenance of various types of planned or previously constructed

projects. The basic principles and techniques of hydrographic surveying are alsoemployed in positioning other marine construction and investigative platforms.

The USACE Hydrographic Surveying Engineer Manual was first published in 1991, revised in1994, and revised again in 2002. It is Publication Number EM 1110-2-1003. A catalog of allUSACE Engineer Manuals can be found at

http://www.usace.army.mil/inet/usace-docs/eng-manuals/em.htm

The USACE Hydrographic Surveying Engineer Manual is located online at

http://www.usace.army.mil/inet/usace-docs/eng-manuals/em1110-2-1003/toc.htm

and can be downloaded chapter by chapter and appendix by appendix from that site (a total of 29files).

The purpose of this manual is stated to be:

provides technical guidance for performing hydrographic surveys that supportthe planning, engineering design, construction, operation, mainenance, and

regulation of navigation, flood control, river engineering, charting, and coastalengineering projects. Accuracy standards and quality control critewria are

defined to establish USACE-wide uniformity in performing surveys involvingdredging measurement, payment and acceptance.

This manual has 22 chapters and 5 Appendices. We will consider mainly the following fourchapters.

Chapter 3: Corps Accuracy Standards, quality control, and quality assurance requirements

Chapter 4: Survey accuracy estimates for dredging and navigation projects

Chapter 6: Planning and processing surveys for civil works projects

Chapter 22: Contracted survey Specifications and cost estimates.

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CHS SURVEY STANDING ORDERS

A set of 41 modular specifications, or standing orders for the design and execution ofhydrographic surveys within the Canadian Hydrographic Service, which had been revisedbetween 1985 and 1988, were issued in March 1988.

These capture a typical set of specifications from that era before the revolutions of DGPSpositioning, high-density bathymetric methods, and the conversion to digital data acquisition andproducts. However, it is an indication of the forward-looking approach of the CHS in the case ofdigital data, that some of these standing orders deal specifically with digital data issues.

These standing orders are organized under 11 headings1 Field instructions and reports2 Field sheets3 Surveys horizontal and vertical control

4 Positioning systems5 Sounding6 Reporting dangers7 Fixed and floating aids8 Revisory and special surveys9 Miscellaneous survey requirements10 Management of field records11 Provision and acquisition of technical information and servcies to and from other

agencies

Although many of these standing orders are out of date, many are still relevant (e.g. those under

headings 6 to 9).

Copies of these standing orders, as a set of Acrobat format files, is provided in a sub-directoryfor this unit.

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NOS SPECIFICATIONS AND DELIVERABLES

The latest version of NOS Hydrographic surveys specifications and deliverables was issued inMarch 2003. The introduction reads:

These technical specifications detail the requirements for hydrographic surveys to beundertaken either by National Oceanic and Atmospheric Administration(NOAA) fieldunits or by organizations under contract to the Director, Office of Coast Survey (OCS),National Ocean Service (NOS), NOAA, U.S. Department of Commerce.

The specifications described herein are based in part on the International HydrographicOrganizations Standards for Hydrographic Surveys, Special Publication 44, FourthEdition, April 1998, specifically for Order 1 surveys. Hydrographic surveys classified asOrder 1 is intended for harbors, harbor approach channels, recommended tracks, inlandnavigation channels, coastal areas of high commercial traffic density, and are usually inshallower areas lower than 100 meters water depth. Additional details for the specific

project areas, including any modifications to the specifications in this manual, will beprovided in Hydrographic Survey Letter Instructions for NOAA field units or theStatement of Work for contractors.

This document is available for downloading athttp://nauticalcharts.noaa.gov/hsd/specs/specs.htm

Here is outline of its contents:1. Introduction

1.1. Definition2. Datums

2.1. Horizontal Datum2.2. Sounding Datum

2.3. Time3. Hydrographic Position Control

3.1. Horizontal Position Accuracy3.2. Differential Global Positioning System (DGPS)

3.2.1. DGPS Specifications3.2.2. DGPS Site Confirmation

4. Tides and Water Levels Requirements (Sections 4.1 through 4.4.3)4.1. General Project Requirements and Scope

4.1.1. Scope4.1.2. Objectives4.1.3. Planning and Preliminary Tidal Zoning4.1.4. NOS Control Stations and Data Quality Monitoring4.1.5. General Data and Reference Datum Requirements4.1.6. Error Budget Considerations

4.2. Data Collection and Field Work4.2.1. Water Level Station Requirements4.2.2. Water Level Measurement Systems and Data Transmissions4.2.3. Station Installation, Operation and Removal4.2.4. Tide Staffs4.2.5. Bench Marks and Leveling4.2.6. Water Level Station Documentation4.2.7. Additional Field Requirements

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4.3. Data Processing and Reduction4.3.1. Data Quality Control4.3.2. Data Processing and Tabulation of the Tide4.3.3. Computation of Monthly Means4.3.4. Data Editing and Gap Filling Specifications

4.4. Computation of Tidal Datums and Water Level Datums

4.4.1. National Tidal Datum Epoch4.4.2. Computational Procedures4.4.3. Tidal Datum Recovery4.4.4. Quality Control (Sections 4.4.4 through 4.7)4.4.5. Geodetic Datum Relationships

4.5. Final Zoning and Tide Reducers4.5.1. Water Level Station Summaries4.5.2. Construction of Final Tidal Zoning Schemes4.5.3. Tide Reducer Files and Final Tide Note

4.6. Data Submission Requirements4.6.1. Station Documentation4.6.2. Water Level Data4.6.3. Tabulations and Tidal Datums

4.6.4. Tide Reducers and Final Zoning and Final Tide Note4.6.5. Submission

4.7. Guidelines and References5. Depth Sounding

5.1. Sounding Units5.2. Accuracy and Resolution Standards

5.2.1. Accuracy Standards5.3. Multibeam Sonar Requirements

5.3.1. General5.4. Corrections to Echo Soundings

5.4.1. Instrument Error Corrections5.4.2. Draft Corrections5.4.3. Velocity of Sound Corrections5.4.4. Heave, Roll, Pitch, Heading, and Navigation Timing Error Corrections5.4.5 Error Budget Analysis for Depths

5.5. Quality Control5.5.1. Multibeam Sonar Calibration5.5.2. Positioning System Confidence Checks5.5.3. Crosslines5.5.4. Multibeam Sun-Illuminated Digital Terrain Model (DTM) Images

6. Towed Side Scan Sonar6.1. Coverage6.2. Side Scan Acquisition Parameters and Requirements

6.2.1. Accuracy6.2.2. Speed

6.2.3. Towfish Height6.2.4. Horizontal Range6.3. Quality Control

6.3.1. Confidence Checks6.3.2. Significant Contacts6.3.3. Contact Correlation6.3.4. Identification of Potential Field Examinations

7. Other Data7.1. Bottom Characteristics7.2. Aids to Navigation

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8. Deliverables8.1. Field Reports

8.1.1. Progress Sketch8.1.2. Danger to Navigation Report8.1.3. Descriptive Report8.1.4. Descriptive Report Appendices

8.2. Preliminary Smooth Sheet8.2.1. Specifications8.2.2. Cartographic Specifications and Conventions

8.3. Shallow-Water Multibeam Sonar Swath Coverage Plot8.4. Side Scan Sonar

8.4.1. Side Scan Sonar Coverage Plot8.4.2. Side Scan Sonar Contact List and Plot8.4.3. Sonargrams

8.5. Digital Data Files8.5.1. Media8.5.2. Single-beam Data8.5.3. Shallow-Water Multibeam Data8.5.4. Side Scan Sonar Data

AppendicesAppendix 1 NOAA Form 77-12 Tide Station Report & N/OMA121 Form 91-01 Next

Generation Water LevelAppendix 2 NOS Cartographic Codes and SymbolsAppendix 3 NOAA Form 76-35A Descriptive Report Cover SheetAppendix 4 NOAA Form 77-28 Descriptive Report Title SheetAppendix 5 NOAA Form 76-40Appendix 6 Abstract of Times of Hydrography For Smooth Tides or Water LevelsAppendix 7 Example Request for Smooth Tides/Water Levels LetterAppendix 8 Standard Depth Curve Intervals and ColorAppendix 9 Danger to Navigation ReportAppendix 10 Data Acquisition and Processing Reports

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NOS STATEMENT OF WORK

This document Statement of work: shallow water multibeam sonar and side scan sonar surveyservices is provided on the NOAA website at

http://chartmaker.ncd.noaa.gov/staff/prodserv.htm

as an example of a typical Statement of Work (SOW) that NOAA uses for specifying

hydrographic surveying requirements.

The stated purpose of a typical contract is:

The purpose of this contract is to provide NOAA with modern, accurate hydrographicsurvey data acquired using shallow water multibeam and side scan sonar technology

with which to update the nautical charts of the assigned area. Numerous obstructions

have been reported in this area. Side scan sonar shall be used to locate theseobstructions and a shallow water multibeam sonar system shall be used to determine the

least depth over the obstructions as well as determine the depths over the entire projectarea. Because the results of this survey will be portrayed on nautical charts, the survey

products must be traceable to and reconstructible from the original raw data.

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CLCS GUIDELINES

On 13 May 1999, the United Nations Commission on the Limits of the Continental Shelf (CLCS)adopted the Scientific and technical guidelines which it had been developing over the previousyear or so. These guidelines are intended for those coastal states which are preparing extendedcontinental shelf claims to be submitted to the commission.

This 91-page document is organized into 10 chapters1 Introduction2 Entitlement to an extended continental shelf, and the delineation of its outer limits3 Geodetic methodologies and the outer limits of the continental shelf4 The 2500 m isobath5 Foot of the continental slope determined as the point of maximum change in the gradient

at its base6 Foot of the continental slope determined by means of evidence to the contrary to the

general rule7 Ridges8 Delineation of the outer limits of the continental shelf based on sediment thickness9 Information on the limits of the extended continental shelf10 References and bibliography

The guidelines can be downloaded from the CLCS website

http://www.un.org/Depts/los/tempclcs/docs/clcs/CLCS_11A1.htm

A copy, in Acrobat format, is provided on the directory for this unit.

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NAVO HYDROGRAPHIC PROCEDURES

This document was prepared between 1988 and 1990, and much of it is out of date, althoughsome sections are still relevant. It was for the use of employees of the US Naval

Oceanographic Office, using NAVO vessels and equipment. It was not meant toi replace the

hyhdrographers judgement, but any deviation from these procedures had to be explained anddocumented. It was designed to amplify the then-current NOAA hydrographic manual, which is

also now out of date.

The ten sections in the original document were

1 Survey planning2 Hydrographic project instructions and specifications development

3 Geodesy

4 Tides

5 Positioning systems

6 Survey operations7 Manual data processing

8 Automated data processing

9 Administrative requirements10 Hydrographic procedure forms

A few parts from sections 2, 3, 6, 7 and 9 are considered still applicable, and have been scanned

into a single Acrobat document (149 pages long). This is provided on the directory for this unit.

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LINZ PROVISIONAL MULIBEAM SPECIFICATIONS

IHO S44 specifications are performance standards, and are not intended to describeappropriate procedures by which the required performance can be achieved. This is left up toeach hydrographic organization to define. Many sets of such procedures have been developedfor IHO S44 (3rd edition 1987), but so far very few for IHO S44 (4th edition, 1998). Also,although the document claims otherwise, IHO S44 is developed almost exclusively for SOLAStype surveys, although IHO S44 is often cited (inappropriately in my opinion) for many otherkinds of survey.

Land Information New Zealand (LINZ) has responsibility for administering the purchase ofhydrographic and bathymetric information (but not to perform any of the surveys). The RoyalNew Zealand Navy (who once had total control over NZ hydrography) now submits bids onhydrographic survey work funded by LINZ, in competition with any other commercial (orforeign government) contractor who wishes to compete for the work.

LINZ mandate is broader than nautical charting. In July 1997, LINZ assumed responsibility forNew Zealand's Continental Shelf Delimitation Project, including surveys in preparation for aclaim to the United Nations for an extended continental shelf, according to UNCLOS-III Article76. Multibeam sonar is likely to be used (RNZN recently outfitted a vessel with a multibeamsystem, and other potential contactors have proposed using multibeam sonar as well).

LINZ asked John Hughes Clarke to prepare specifications particularly for the design andassessment of a survey using multibeam sonar echosounders. Specifications for other requiredsurvey measurements, such as positioning, tides and operator competence were not addressed.Johns report (LINZ TH Technical Report #2, August 1999) is available on his website

A copy of this 46-page report, in Acrobat format, is provided in the directory for this unit.

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DGPS DATA FORMAT STANDARDS:

RTCM SC-104

The Radio Technical Commission for Maritime Services (RTCM) is an organization of industryand user stakeholders, which addresses issues concerning radio communications at sea.

Starting in the early 1980s this organization began discussing the data structures, which would

be needed to provide effective real-time differential corrections for GPS navigation. Sub-Committee 104 was formed, known as RTCM SC-104, and the data structure specifications

which they developed have come to be known as the RTCM SC-104, or simply RTCM formats.

The RTCM SC-104 message formats are designed to broadcast real-time differential GPS

correction data from a reference station to a DGPS user (rover receiver), using any convenientradio link. Version 1.0 of these standards was published in 1986. The current version is 2.2,

dated January 1998.

Because they were involved in the discussions from the beginning, most major GPS

manufacturers adopted the RTCM standard as soon as DGPS products began to be produced.This has contributed to the widespread success and adoption of DGPS services, since any

(RTCM-capable) brand of GPS receiver can use DGPS corrections measured and broadcast

using any other (base-station-capable) brand of receiver.

The RTCM standard defines formats for a few dozen different message types. However theprimary DGPS message type is Type 1 (or the more efficient equivalent Type 9) messages,

which provide range and range rate corrections for pseudoranges measured for each of the

satellites being tracked at the base station.

The RTCM specification document can be obtained from:

Radio-Technical Commission for Maritime Services

P.O.B. 19087

Washington, D.C. 20036

(202) 639-4006

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DGPS DATA FORMAT STANDARDS:

NMEA 0183

The National Marine Electronics Association states that

We are the unifying force behind the marine electronics industry. Bringing

together all aspects of the industry for the betterment of all is our business.

The NMEA 0183Standard for Interfacing Marine Electronics Devices is a

voluntary industry standard, first released in March of 1983. The NMEA 0183Standard defines electrical signal requirements, data transmission protocol,

timing and specific sentence formats for a 4800 baud serial data bus.

The Standard has been updated from time to time and the latest release, in July

2000, is Version 3.0.

More details about NMEA and its products can be found at:

http://www.nmea.org/

We will be considering data formatted according to some of the NMEA sentences later in thecourse.

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THE STANDARDS OF COMPETENCE FOR

HYDROGRAPHIC SURVEYORS

This standard is published by the IHO as Publication No. M-5, and has evolved through eighteditions since first appearing in 1978. It is prepared and revised by an eight-memberFIG / IHOInternational Advisory Board on Standards of Competence for Hydrographic Surveyors. Thepurpose of these standards is stated to be:

To provide guidance whereby individual surveyors may be trained and qualified in accordancewith internationally accepted levels of competence.

The document has several pages of preamble describing the procedures for recognizing that aparticular training program achieves the standards contained in this publication. This is followedby a detailed model syllabus for the training of hydrographic surveyors. This syllabus is in three

parts. For the Ninth Edition (release date Spring 2001) these parts contain:

Four Basic subjects (Mathematics and statistics; Computing; Physics, Nautical Science).

Seven Essential subjects (Bathymetry; Water levels and flow; Positioning; Hydrographicpractice; Hydrographic data management; Environmental science; and Legal Aspects).

Seven Optional units (Nautical charting, Coastal Zone Management; Offshore Seismic;Offshore construction; Remote sensing; Military; Inland waters).

A copy of the current (Eighth) edition of M5 is provided in the directory for this unit.

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THE INTERNATIONAL ORGANIZATION FOR

STANDARDS (ISO)

The ISO is the lead organization in the World Standards Services Network, which also includethe International Electrotechnical Commission (IEC) and the International Telecommunications

Union (ITU), as well as another 40 or so international standardizing bodies (for example the

International Maritime Organization).

Most ISO standards are technical or engineering standards, for example, those which specify the

dimensions and tolerances for bolts, nuts, screws, pins and rivets, allowing the world to

standardize the supply and use of these fasteners, keeping much of our world from falling apart.

Recently (1987) ISO ventured into a very different kind of standard: generic managementsystems standards, which are applicable to any organization (private company, government

agency, public administration), large or small, providing either products or services.Management system standards provide a model to follow in setting up and operating a

management system, using state-of-the-art practices. These standards are known as the ISO9000 family, and consist of standards and guidelines relating to management systems, and

related supporting standards on terminology and specific tools, such as auditing.

ISO 9000 is primarily concerned with "quality management". The ISO definition of "quality"

refers to all features of a product (or service) which are required by the customer. "Qualitymanagement" means what the organization does to ensure that its products conform to the

customers requirements. ISO 9000 is NOT concerned with products and product standards

(directly at least), but is rather concerned with an organizations (management) processes, which

will affect whether or not everything has been done to ensure that the product meets thecustomers requirements.

ISO 9000 is generic. No matter what the organization is or does, the essential features of a

quality management system are spelled out in ISO 9000.

An informal description of the ISO 9000 process is Say what you do. Do what you say.Document it.

For more details, see

http://www.iso.ch/

ISO/IEC 8211:1994Information technology -- Specification for a data descriptive file for information interchange

Edition: 2 (monolingual)

Number of pages: 69Price code: V

Technical committee / subcommittee: JTC 1

ICS: 35.080

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INTERNATIONAL MARINE CONTRACTORS

ASSOCIATION (IMCA)

In November 2001, IMCA published

IMCA S 003 Guidelines for the Use of Multibeam Echosounders (MBES) for Offshore

Surveys

Having the following contents1. Preface

2. Introduction

3. Multibeam echosounders

4. Sub-sea vehicles and systems5. Calibration tests

6. MBES data processing7. Standards for MBES surveys

8. Survey planning9. Terminology

10. Bibliography

This publication is available for purchase from IMCA at 60 / copy (15 for IMCA members).

The IMCA guidelines were prepared by Ed Danson, Andy McNeill, Eric Primeau, and WillPrimavesi, with input from Carl Sonnier, Gordon Johnston, Bent Warming Hansen, Graham

Cooper, Richard Green, and David Shand. It draws on the following publications (some of

which are discussed earlier in these notes):

Mike Brissette and John Hughes Clarke Sidescan versus multibeam echosounder objectdetection

Mike Brissette The applications of multibeam sonars in route survey

S Cowls and B Fogg How to chose a multibeam

B W Hansen Seabed mappingLloyd Huff Shallow water multibeam systems

Lloyd Huff HPR and dynamic vessel corrector

John Hughes Clarke Provisional swath sonar survey specifications. (for Land Information New

Zealand)John Hughes Clarke Field calibration; the patch test and the reference surface

IHO Special Publication No 44: Standards for Hydrographic Surveys, 4th edition

Mike Kalmbach Multibeam patch testLand Information New Zealand Hydrographic MBES Survey Standards. TH23 Version 2.2

National Ocean Service Hydrographic Surveys Specifications and Deliverables

I Sinclair and P Edge Swathe bathymetry systems: practical experience in deriving operating

standards

C Sonnier Calibration of multibeam echosounders

US Army Corps of Engineers & NOAA Multibeam Surveying Workshop

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US Army Corps of Engineers Calibration procedures for multibeam sonar systems-Technical

letter 1130-2-1US Army Corps of Engineers Hydrographic Surveying, Engineer Circular 1130-2-210

Following is a review of this publication, taken from the IMCA website at

Although multibeam echosounders (MBES) have been in use since the 1960s, their track recordin commercial marine operations has can be traced back only as far as the 1990s. The growth in

their use has been, in part, due to the ability of these instruments to cover wide swathes of the sea

floor in a single pass.

With high-resolution bathymetry obtainable over wide areas and with acoustic frequenciesranging from 10kHz to over 500kHz, multibeam echosounders offer the potential for great

accuracy and provide detailed sea floor imagery with scales of economy unavailable from

traditional single-beam echosounders.

At the time of publication, some 700 systems had been built by at least ten manufacturers world-wide, of which more than 40% had gone into commercial operations.

However, no specifications or guidelines could be found that specifically addressed the use of

MBES for offshore surveying. IMCA's Offshore Survey Division Management Committee

established a workgroup to oversee the development of these guidelines, as a means ofaugmenting existing (in the main more general) documentation and to provide a guide for future

specifications.

The guidelines draw heavily on a number of existing standards and published papers by persons

eminent in their field and were distributed widely for consultation among key users and clientgroups prior to publication. IMCA was particularly pleased to receive the endorsement of

UKOOA's Survey & Positioning Committee following its valuable collaboration, review and

input.

It is intended to review and update the guidelines on a regular basis - users of the document are

encouraged to forward their comments to IMCA.

Documents

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