1

The two main websites I check CRS info disagree about what the CRS EPSG:2901 is intended for.

Curious whether anyone can shed some light on this conflict.

https://epsg.io/2901-area says Australia

https://spatialreference.org/ref/epsg/2901/ says Montana in the United States

Improve this question
6
  • 1
    they don't disagree. See here. Note that this link is for the projection, while yours is for "area"
    – JGH
    Commented Jul 8, 2021 at 15:14
  • so the string "EPSG:2901" is ambiguous between an area and a projection? What exactly is an area?
    – Hugh_Kelley
    Commented Jul 8, 2021 at 15:17
  • 1
    I will leave that to EPSG database expert, I can only speculate the "area" is a predefined bounding box. I don't see them being ambiguous though since they refer to different things, they just happen to share the same ID. The "area" is not a projection so it is not possible to use it as such
    – JGH
    Commented Jul 8, 2021 at 15:22
  • seems like it might be australia specific epsg.io/?q=Australia%20kind%3AAREA
    – Hugh_Kelley
    Commented Jul 8, 2021 at 15:26
  • no, there are 3500 of them, everywhere
    – JGH
    Commented Jul 8, 2021 at 16:45

1 Answer 1

Reset to default
3

EPSG.io and spatialrefenece.com are third party web sites, for definitive information on EPSG codes you should probably use the official EPSG registry ~ EPSG Geodetic Parameter Dataset

Searching with 2901 on the EPSG registry shows us that the code is used for both a CRS

https://epsg.org/crs_2901/NAD83-HARN-Montana-ft.html?

and an Extent

https://epsg.org/extent_2901/Australia-138-E-to-144-E-8-S-to-12-S-SC54-onshore.html

In the EPSG registry, all geodetic parameters are codified, not just CRS, you can see from the search results parameters that have codes.

List of EPSG parameters

So if we look at the CRS NAD83-HARN-Montana-ft

NAD83-HARN-Montana-ft

We can see that the code for the CRS is 2901, that it is projected, that it acts on an Extent USA - Montana which has a code 1395

and if we explore further in the HTML page we can see that the coordinate system used is Cartesian 2D CS. Axes: easting, northing (X,Y). Orientations: east, north. UoM: ft. which has a code 4495.

It uses a BASE CRS NAD83(HARN) with code 4152

it uses the SPCS83 Montana zone (International feet) CONVERSION which has a code 15338

etc. etc.

The WKT2 gives us a summary of this too:

https://epsg.org/crs/wkt/id/2901

PROJCRS["NAD83(HARN) / Montana (ft)",BASEGEOGCRS["NAD83(HARN)",DATUM["NAD83 (High Accuracy Reference Network)",ELLIPSOID["GRS 1980",6378137,298.2572221,LENGTHUNIT["metre",1,ID["EPSG",9001]],ID["EPSG",7019]],ID["EPSG",6152]],ID["EPSG",4152]],CONVERSION["SPCS83 Montana zone (International feet)",METHOD["Lambert Conic Conformal (2SP)",ID["EPSG",9802]],PARAMETER["Latitude of false origin",44.25,ANGLEUNIT["degree",0.0174532925199433,ID["EPSG",9102]]],PARAMETER["Longitude of false origin",-109.5,ANGLEUNIT["degree",0.0174532925199433,ID["EPSG",9102]]],PARAMETER["Latitude of 1st standard parallel",49,ANGLEUNIT["degree",0.0174532925199433,ID["EPSG",9102]]],PARAMETER["Latitude of 2nd standard parallel",45,ANGLEUNIT["degree",0.0174532925199433,ID["EPSG",9102]]],PARAMETER["Easting at false origin",1968503.937,LENGTHUNIT["foot",0.3048,ID["EPSG",9002]]],PARAMETER["Northing at false origin",0,LENGTHUNIT["foot",0.3048,ID["EPSG",9002]]],ID["EPSG",15338]],CS[Cartesian,2,ID["EPSG",4495]],AXIS["Easting (X)",east],AXIS["Northing (Y)",north],LENGTHUNIT["foot",0.3048,ID["EPSG",9002]],ID["EPSG",2901]]

Improve this answer

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.