Talk:Geographic coordinate system

Too many reverts

I see a bit too many reverts, which I suggest end. There are some useful and unuseful bits, so I don't want to add add another revert. Here are a few notes:

• Use of en dash for "west–east" is correct (MOS:ENDASH), so keep these edits.
• There is no primary English variation for this article. Not sure what's best: use all US English, use all British English, or mixed, as this is a globally-focused article. I think it is OK to have it mixed in context, as it was before. So use British English for "but neighbouring Scotland" and American English for "cartographical organization include the North American Datum". More on this MOS:ENGVAR.

+mt 21:00, 25 March 2020 (UTC)

The top of the talk page contains a US English template. Presumably the UK spelling snuck in after the template was added.Jc3s5h (talk) 21:24, 25 March 2020 (UTC)

Thanks, I normally look for {{Use American English}} on the main article, but I see this now on the Talk page. This is fine with me. +mt 23:27, 25 March 2020 (UTC)

Figure is wrong

The figure with the caption "Earth centered, Earth fixed coordinates in relation to latitude and longitude" is wrong -- since this is for an ellipsoid, the radius vector $r$ should not pass through the center of mass of the ellipsoid. See here: https://en.wikipedia.org/wiki/Geographic_coordinate_conversion#/media/File:Geodetic_latitude_and_the_length_of_Normal.svg — Preceding unsigned comment added by 205.204.46.102 (talk) 01:45, 30 August 2020 (UTC)

The diagram is for ECEF, which is not geodetic coordinates. As stated in the article,

The Earth-centered Earth-fixed (also known as the ECEF, ECF, or conventional terrestrial coordinate system) rotates with the Earth and has its origin at the center of the Earth.

Strebe (talk) 03:14, 31 August 2020 (UTC)

Rename??

The name of this page can be confusing, as the specific term GCS is commonly used only for the spherical (lat/lon) coordinates, as opposed to planar or projected coordinate systems (e.g., in ArcGIS and some textbooks). The generic term is just "coordinate system" in geography, so perhaps it should be Coordinate System (Geography), with a section or separate page focusing on GCS (lat/lon). That said, I've always thought such a co-option of the generic term GCS for one type is unfortunate, but it is not my decision. Maybe we should just follow the crowd and start calling lat/lon "GPS coordinates" ;-) Bplewe (talk) 16:01, 22 November 2021 (UTC)

Oppose. Bplewe has not offered sufficient proof, with citations to reliable sources, that the term "geographic coordinate system" only applies to latitude and longitude, and excludes other terrestrial coordinates such as projected coordinates, Cartesian coordinates coordinates etc. Also, it is not clear tom me that "Coordinate System (Geography)" would be any better than "Geographic coordinate system".

Support. “Geographic coordinate system” as used in GIS these days refers to spherical coordinates with a datum. I think this is an Esri convention that has pretty much taken over. The literature, historically, refers to “geographic(al) coordinates” (without “system”) to mean latitude and longitude; no such term as “geographical coordinate system” seems to have been in common use before GIS. Yes, we need references, but the reference will support this change. Strebe (talk) 19:11, 22 November 2021 (UTC)

It's not clear that we should decide only on the basis of GIS nomenclature. Some other points of view are astronomy and geography as an academic subject. Looking around, I discovered that Earth-centered, Earth-fixed coordinate system essentially covers (or should cover) the same material, but is a bit more astronomy-oriented. The two articles should probably be merged. Jc3s5h (talk) 21:51, 22 November 2021 (UTC)

If the term “geographic coordinate system” was not defined before it came into use in GIS, and is in use nowhere else, then I think we should decide “only on the basis of GIS nomenclature”. The closest I can find routinely in the literature before GIS is “geographic coordinate(s)”, which always seems to refer to latitude/longitude. I don’t think ECEF the should get merged with this one. The ECEF article is woefully incomplete and inadequate; I think it should get fleshed out. Strebe (talk) 01:55, 23 November 2021 (UTC)

I totally agree with not changing the terminology solely because ArcGIS does so, and thanks Daan for making me do my homework (and also thanks for being the watchdog over this subdiscipline, every one should have someone as conscientious). There does seem to be an emerging consensus, encapsulated in EPSG, ISO 19111 and the corresponding OGC AS-2, and I would propose that we should conform to their terminology as the baseline. As annoyed as I am about the confusing way that ArcGIS uses these terms in its interface, it does technically conform to these standards. These all define the following (OGC AS-2 Section 9):

• Coordinate system is a generic term for a framework for measuring locations, not necessarily geographic
• Coordinate reference system is a standardized coordinate system for measuring geographic locations, a coordinate system along with a choice of horizontal datum. Spatial reference system is also used a lot here.
• Geographic CRS measures location using ellipsoidal coordinates (lat/lon on a choice of ellipsoid model, maybe + HAE)
• Geocentric CRS = Earth Centered Earth Fixed
• Projected CRS measures location on a planar surface created by a map projection
• and a bunch of others including local-context "Engineering CRS", image coordinates, etc.

So my revised proposal is to improve Spatial reference system to be the overall umbrella, and focus this page on lat/lon+datum, with the existing title. Grid reference system should probably be revised slightly to conform; should it be renamed to Projected Coordinate System?Bplewe (talk) 00:33, 24 November 2021 (UTC)

Refocused

Since there was no objection to my proposal, I have refocused this page with respect to Spatial reference system, Grid reference system, and Earth-centered, Earth-fixed coordinate system, so that this page focuses specifically on latitude/longitude, which is how the term is used in the international standards mentioned above. It could still use some improvement, though. Bplewe (talk) 02:44, 18 December 2021 (UTC)

Geography

What is meant by geographic coordinate system?who introduced it? 2405:EC01:1001:2B61:FEF:BAB5:6097:67FC (talk) 04:52, 12 June 2022 (UTC)

@2405:EC01:1001:2B61:FEF:BAB5:6097:67FC its a worldwide corrdinates and idk either who introduced it 2601:680:8300:3870:ACD0:3995:CC1D:3CEF (talk) 05:28, 25 January 2024 (UTC)

North South East West

One often sees e.g. +/-Y° and +/-X° instead of °N/S and °E/W. If there are one or more standards for this, I think it might be helpful to discuss this topic on the page. 142.92.29.46 (talk) 19:05, 12 February 2024 (UTC)

Good point. Strebe (talk) 23:04, 12 February 2024 (UTC)

Do you have some example sources? –jacobolus (t) 23:46, 12 February 2024 (UTC)

Not off the top of my head. But I have encountered it in the past. I came here looking to confirm which is "standard" (I think + is usually N and E) and found nothing. 142.92.29.45 (talk) 14:35, 13 February 2024 (UTC)

Found one. Look at the +/- values given for lat/lon here:

https://geopandas.org/en/stable/docs/reference/api/geopandas.points_from_xy.html 142.92.29.45 (talk) 14:59, 13 February 2024 (UTC)