Mariners’ Guide to Accuracy of Depth Information in Electronic Navigational Charts - Edition 1.0.0 - Published Edition September 2020

Oct 12, 2026

Edition 1.0.0 (September 2020) by the International Hydrographic Organization presents guidance on how depth information should be accurate in electronic navigational charts (ENC). The publication summarizes depth accuracy concepts, defines accuracy levels for paper charts and ENCs, and explains quality descriptions for charted objects affecting safe navigation. It also introduces Zones of Confidence (ZOC), discusses impacts on mariners, and provides assessment methods for evaluating survey quality and survey position accuracy.

LanguageEnglish

CategoryGeneral

FormatPDF

Pages28

Reading Time10 min

AccessFree to download

1 Introduction

1.1 Abbreviations

2 Executive summary and recommendations

3 Accuracy of depth information in paper charts

4 Accuracy of depth information in Electronic Navigational Charts

4.1 Generalized information

4.1.1 High accuracy depth information

4.1.2 Medium accuracy depth information

4.1.3 Poor accuracy depth information

4.2 Quality descriptions of individual objects dangerous to safe navigation

4.2.1 Obstructions

4.3 Survey reliability

4.4 Depth accuracy in relation to charted depth

4.4.1 Safety contour

5 Zones of Confidence symbols in ENCs

5.1 Impact of ZOC categories upon mariners

5.1.1 Effect of over-scaling

6 Assessment of the quality of a survey into a Zone of Confidence by the Hydrographic Office

6.1 Assessment examples

6.2 Position accuracy of a survey

S-67 Mariners’ Guide to Accuracy of Depth Information in Electronic Navigational Charts (ENC) Edition 1.0.0 – September 2020 Published by the International Hydrographic Organization 4b quai Antoine 1er Principauté de Monaco Tel: (377) [93.10.81.00](93.10.81.00) Fax: (377) [93.10.81.40](93.10.81.40)[ ](93.10.81.40)[info@iho.int](info@iho.int)[ ](info@iho.int)[www.iho.int](www.iho.int) © Copyright International Hydrographic Organization 2020 This work is copyright. Apart from any use permitted in accordance with the Berne Convention for the Protection of Literary and Artistic Works (1886), and except in the circumstances described below, no part may be translated, reproduced by any process, adapted, communicated or commercially exploited without prior written permission from the International Hydrographic Organization (IHO) Secretariat. Copyright in some of the material in this publication may be owned by another party and permission for the translation and/or reproduction of that material must be obtained from the owner. This document or partial material from this document may be translated, reproduced or distributed for general information, on no more than a cost recovery basis. Copies may not be sold or distributed for profit or gain without prior written agreement of the IHO and anyother copyright holders. In the event that this document or partial material from this document is reproduced, translated or distributed under the terms described above, the following statements are to be included: “Material from IHO publication [reference to extract: Title, Edition] is reproduced with the permission of the International Hydrographic Organization (IHO) Secretariat (Permission No / ) acting for the IHO, which does not accept responsibility for the correctness of the material as reproduced: in case of doubt, the IHO’s authentic text shall prevail. The incorporation of material sourced from the IHO shall not be construed as constituting an endorsement by IHO of this product.” “This [document/publication] is a translation of IHO [document/publication][name]. The IHO has not checked this translation and therefore takes no responsibility for its accuracy. In case of doubt the source version of [name] in [language] should be consulted.” The IHO Logo or other identifiers shall not be used in any derived product without prior written permission from the IHO Secretariat. Document Control Changes to this Product Specification are coordinated by the IHO Data Quality Working Group (DQWG) which is a Working Group of the IHO Hydrographic Services and Standards Committee (HSSC) . New editions will be made available via the IHO web site. | Edition
Number | Date | Author | Purpose | | --- | --- | --- | --- | | 0.4 | April 2017 | DQWG | Draft document for discussion (DQWG- 12) | | 0.5 | August 2017 | DQWG | Review by correspondence | | 0.6 | July 2018 | DQWG | Review by correspondence | | 0.7 | September 2018 | DQWG | Review results included | | 0.8 | May 2019 | DQWG | Australian comments included | | 0.9 | February 2020 | DQWG | Draft for WG approval | | 1.0.0 | March 2020 | DQWG | Version for approval by HSSC-12 | | 1.0.0 | July 2020 | DQWG | Final draft. | | 1.0.0 | September 2020 | DQWG | Published Edition 1.0.0 | | | | | | | | | | | Page intentionally left blank TABLE OF CONTENTS 1 Introduction ................................................................................................................................. 2 1.1 Abbreviations .............................................................................................................................. 2 2 Executive summary and recommendations................................................................................ 3 3 Accuracy of depth information in paper charts ........................................................................... 4 4 Accuracy of depth information in Electronic Navigational Charts ...........

FAQs

What is the purpose of the Mariners’ Guide in this edition?

It provides guidance on the accuracy of depth information in electronic navigational charts (ENC), including how accuracy levels and quality descriptions support safe navigation.

How does the guide treat depth accuracy for paper charts versus ENCs?

It covers accuracy of depth information in paper charts, then separately explains accuracy in ENCs and how generalized information and depth-related concepts (e.g., safety contour) relate to charted depth.

What are Zones of Confidence (ZOC) and how do they affect mariners?

The guide introduces ZOC symbols in ENCs and explains how ZOC categories influence mariners, including the effect of over-scaling.

Oct 12, 2026

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