INTERNATIONAL HYDROGRAPHIC ORGANISATION HYDROGRAPHIQUE

ORGANIZATION INTERNATIONALE

NAUTICAL CARTOGRAPHY WORKING GROUP

(NCWG)

[A Working Group of the Hydrographic Services and Standards Committee (HSSC)]

Chair: Jeff WOOTTON
Australian Hydrographic Service
8 Station Street, Wollongong, NSW, 2500
Australia / Secretary: Andrew HEATH-COLEMAN
United Kingdom Hydrographic Office
Admiralty Way, Taunton, Somerset
United Kingdom
Tel: +61 2 4223 6508 / Tel: +44 1823 337900 ext 3656
Email: / Email:

NCWG Letter: 11/2015

UKHO ref: HA317/010/031-12

AHS ref: fAA158624; fAA155641

Date 08 October 2015

Dear Colleagues

Subject: Low water line or drying line? Clarification to S-4 (Follow-up to Letter 05/2015).

Thank you to the 19 Working Group members and ESRI who responded to NCWG Letter 05/2015. All responses supported the proposed clarifications to S-4 which will therefore be included in the next revision.

Only two comments were added to the response form. These are recorded in Annex A, with my response.

There is no need to respond to this letter.

Yours sincerely,

Jeff Wootton,

Chair NCWG.

Annex A: Further comments received to NCWG Letter 05/2015


Annex A to NCWG 11/2015

Low water line or drying line? Clarification to S-4

Further comments received to NCWG Letter 05/2015

IRAN

In all Nautical Charts (both electronic and paper charts) which are provided by I.R of Iran, the zero meter contour refers as a Low water Line (not drying line). So we would suggest a unique format for all national and international charts.

Chairman: I believe this is precisely why we are making this clarification

US

Since NCWG Letter 05/2015 has compelled all of us to take a closer look at INT1 H-20, I thought I would take the opportunity to show how the diagram in U.S. Chart No. 1 differs from INT1.

We have found the diagram useful to show other height related features, such as the use of underlined numbers for drying heights, the typical depiction of heights on islets (bare rocks), as well as topographic contours, index contours, and spot heights. The U.S. also uses a wavy line to distinguish the moving "sea surface at any time" for the various "fixed" datum lines.

U.S. Chart No. 1, H-20

INT1, H-20

Chairman: The INT1 subWG could consider whether it is useful to add more detail to H-20. A couple of inconsistencies between the US Chart 1 version of H20 and conventions specified in S-4 have also been noted, which I will discuss with US offline.