How many CRS / EPSG codes are there?

Question

I assume the answer to the number of CRS is "nobody knows", given that everybody can define their own CRS willy-nilly.

So maybe it's better to ask: How many EPSG-registered CRS are there? I haven't found an easy way to scrape the total number of EPSG codes in the various lookup tools.

Are there other well-endowed libraries of CRS such as EPSG? If so, how many CRS do they entail?

Answer 1

As of EPSG Geodetic Parameter Dataset v9.3 (it's now up to 9.4.1 online), there are 5822 coordinate reference systems. This includes projected, geographic/geodetic, vertical, and a few engineering ones. Newer geographic/geodetic will include 2D, 3D, and geocentric/3D Cartesian versions.

There are also 760 deprecated CRS.

Disclosure: I'm on the subcommittee that maintains the EPSG Registry.

Answer 2

If you want a lookup tool, you might want to consider looking at the Open Geospatial Consortium (OGC) CRS Definition Resolver, which is implemented using Rasdaman SECORE (Semantic Coordinate Reference System Resolver).

The OGC CRS Name Resolver is accessible at the following service endpoints: ​

• http://www.opengis.net/def/axis (for Axis Identifier URLs)
• ​http://www.opengis.net/def/crs (for CRS Identifier URLs and CRS Template URLs)
• ​http://www.opengis.net/def/crs-compound (for Compound CRS URLs)
• ​http://www.opengis.net/def/equal (for semantic CRS URL comparison)
• ​http://www.opengis.net/def/crs-query (for general XQuery requests)

Ref: http://rasdaman.org/wiki/SecoreUserGuide

Note it doesn't resolve all EPSG code versions, or URN identifiers generally. It gives access to EPSG codes and OGC codes inter al.

Answer 3

There are 9.906 different spatial references on http://spatialreference.org/ref/?page=199 available. The front page says "4362 EPSG references" but also the last update was in year 2013.

Answer 4

epsg.io is a modern webservice, which is "Powered by EPSG database 9.4", the current registry, but also has other CRS definitions. You can browse the source code, including their SQLite database gml.sqlite, which contains the URN identifier (e.g. urn:ogc:def:crs:EPSG::4326), and the source xml used to define each CRS.

Here is my tally query for the different CRS types:

SELECT substr("xml", 6, instr("xml", ' ') - 6) AS crs_type,
       deprecated, count(*) AS count
FROM gml
WHERE id LIKE '%crs%'
GROUP BY crs_type, deprecated
ORDER BY crs_type, deprecated;

crs_type     deprecated  count     
-----------  ----------  ----------
CompoundCRS  false       269       
CompoundCRS  true        7         
Engineering  false       20        
Engineering  true        2         
GeodeticCRS  false       778       
GeodeticCRS  true        400       
ProjectedCR  false       4666      
ProjectedCR  true        350       
VerticalCRS  false       207       
VerticalCRS  true        1   

There are extra codes from PROJ, including 474 from esri.extra, and 21 in other.extra. So I guess the full tally of CRS definitions at http://epsg.io is 7195.

Answer 5

This helps explain why at least three of the CRS registers exist: https://committee.iso.org/files/live/sites/tc211/files/Resources/GuideToCRSRegistries3.pdf

(Peter Parslow, chair of ISO/TC 211)

Answer 6

Spatialreference knows 4362 EPSG-codes.

Answer 7

Esri, as of ArcGIS Pro 2.3 alpha and ArcGIS Desktop 10.7 alpha (so far only a few new objects have been added), has:

projected crs: 5467
geographic crs: 734
vertical crs: 305

I think the counts omit deprecated objects.

Note: Esri only has 2D geographic CRS (unlike EPSG) but does have ellipsoidal height-based vertical CRS that are combined with a 2D geographic CRS to make the equivalent of an EPSG 3D geographic CRS. Esri also have a bunch of custom Minnesota geographic CRS. They're used in a set of county-level projected CRS that try to minimize the grid-vs-ground differences due to the projections.

Disclosure: I work for Esri.