Talk:Admiralty chart

Maps Low‑importance

	This article is within the scope of WikiProject Maps, a collaborative effort to improve the coverage of Maps and Cartography on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.MapsWikipedia:WikiProject MapsTemplate:WikiProject MapsMaps articles
Low	This article has been rated as Low-importance on the project's importance scale.

Oceans Low‑importance

This article is within the scope of WikiProject Oceans, a collaborative effort to improve the coverage of oceans, seas, and bays on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.OceansWikipedia:WikiProject OceansTemplate:WikiProject OceansOceans articles

Low

This article has been rated as Low-importance on the project's importance scale.

WikiProject Oceans To-do List:

Here are some tasks awaiting attention:

Article requests : List of oceanographers, create a comprehensive article on Concentrations of marine debris out of all the gyre and "garbage patch" articles
Copyedit : Draft:Terrance (octopus)
Expand : Coral Sea, Endeavour Strait, Greenland Sea, Solomon Sea
Photo : find images for Category:Wikipedia requested photographs in the oceans
Stubs : Oceanography stub articles, Marine geography stub articles, Aleutian Trench, Bellingshausen Sea, Caernarfon Bay, Gerlache Strait, Gulf of Oman, Iceland Sea, Draft:Terrance (octopus)
Update : Botany Bay, Wilkins Sound, Mariana Trench, Challenger Deep
Verify : Antarctic Circumpolar Current, Bering Sea, Gulf of Aden, Iceberg B-15, Ionian Sea, Japan Trench, Moreton Bay, Sound (geography), Timor Sea
Other : add ISBNs and remove excessive or inappropriate external links from Aral Sea; check La Belle (ship) for GA status; improve citations or footnotes and remove excessive or inappropriate external links from MS Estonia

External links modified

Hello fellow Wikipedians,

I have just modified 2 external links on Admiralty chart. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:

When you have finished reviewing my changes, please set the checked parameter below to true or failed to let others know (documentation at {{Sourcecheck}}).

This message was posted before February 2018. After February 2018, "External links modified" talk page sections are no longer generated or monitored by InternetArchiveBot. No special action is required regarding these talk page notices, other than regular verification using the archive tool instructions below. Editors have permission to delete these "External links modified" talk page sections if they want to de-clutter talk pages, but see the RfC before doing mass systematic removals. This message is updated dynamically through the template {{source check}} (last update: 5 June 2024).

If you have discovered URLs which were erroneously considered dead by the bot, you can report them with this tool.
If you found an error with any archives or the URLs themselves, you can fix them with this tool.

Cheers.—InternetArchiveBot (Report bug) 12:02, 4 October 2016 (UTC)[reply]

Transverse Mercator Projection

The article states: In contrast, coastal charts use the transverse Mercator projection, in order to depict the shape of the shoreline with greater accuracy.[2] This does not sound right at all. In general standard and transverse Mercator (SM, TM) maps should have the same amount of distortion, but differently distributed. For SM, the scale is constant along a line of latitude (E-W), but changes as you go N or S away from that line. For TM, the scale is constant along the central meridian (N-S) but changes as you go E or W away from that line. So TM has an advantage for areas that have greater N-S extent than E-W. This is the case for the National Grid (Great Britain) which uses a rectangle that is 1300 km from N to S and 700 km from E to W, and the grid uses transverse Mercator for that reason.

The reference cited in the article (The RYA navigation handbook, Bartlett) states that Admiralty large scale maps such as harbour plans use the TM projection, but does not give a reason. It's unlikely to have anything to do with distortion, which is minimal for a map covering a few km whether SM or TM is used. I suspect that these large scale charts use Ordnance Survey mapping, and so just use the same projection as the OS maps on which they are based. I haven't found a source to support (or refute) this yet. I'll keep looking. Kognos (talk) 13:00, 2 September 2019 (UTC)[reply]

I've checked in both the 1938 and 1987 editions of the Admiralty Navigation Manual, which has answered some of my questions. I've modified the text accordingly and added references Kognos (talk) 21:15, 20 January 2020 (UTC)[reply]

History

I've added a history section, dealing with chart production and surveys over the years since the establishment of the Hydrographic Office. I've removed the list of survey ships - this topic is covered by the separate article List of survey vessels of the Royal Navy. I've removed the chart of Somalia, which doesn't seem to connect to anything. I've not changed the section on features except for an introductory sentence. This could use some expansion, but it would need to be by someone whe knows more about electronic charts than I do. All comments welcome. Kognos (talk) 20:33, 23 December 2021 (UTC)[reply]