[Proj] Esri & EPSG Proj codes

Frank Warmerdam warmerdam at pobox.com
Sat Sep 10 11:39:54 EST 2011

On 11-09-10 09:12 AM, Irwin Scollar wrote:
> Melita Kennedy wrote in reply to my query concerning Esri proj codes:
>> There currently is not a complete list available online. The
>> ArcObjects enumeration lists are not complete. These are definitions
>> defined by Esri. Sometimes EPSG adds the definitions later, and then
>> Esri updates the well-known IDs to the EPSG one (as more authoritative).
> The Access database EPSG-v7_9.mdb contains 4924 COORD_REF_SYS
> codes.  4416 of these have Proj data which can be gleaned by
> combining the epsg and esri lists from the NAD directory out of a
> total of 6577 codes in these lists, eliminating "Unknown",
> "Unspecified" and searching for all correspondences between the NAD
> code numbers and the EPSG code numbers.
> How were the esri and esri-extra lists in that directory obtained?


I believe I generated these PROJ.4 init files.  I ran a script to
process a directory full of ESRI projection engine .prj files from
some ESRI product.  This was done a number of years ago and I have
not attempted to update them.

> When EPSG adds definitions defined by Esri, do these get new numbers
> in the EPSG Access database or is there a systematic relationship
> between Esri numbers prior to adoption by EPSG and after
> incorporating them in the EPSG database?

I can't say authoritatively, but I assume they are renumbered.  I believe
ESRI deliberately chooses numbers well outside the EPSG norm and EPSG
assigns numbers in their normal ranges when they incorporate the coordinate
systems into their master database.

Best regards,
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/warmerda
and watch the world go round - Rush    | Geospatial Software Developer

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