Projection parameters made easy

Fri, 10/30/2009 - 23:00 — Robert

Here is a website that makes it easy to get the proj4 coordinate reference system descriptions that DIVA-GIS now uses.

First find the projection you want by browsing or searching in any of the lists (EPSG, ESRI, ...). If you have selected one, click on the "Proj4" link in the gray box.

For example, click the ESRI references link. Search for "Robinson", select "World Robinson", and click on the Proj4 link to get:

+proj=robin +lon_0=0 +x_0=0 +y_0=0 +ellps=WGS84 +datum=WGS84 +units=m +no_defs

Une très heureuse initiative by Howard Butler, Christopher Schmidt, Dane Springmeyer, and Josh Livni. Thanks a lot!

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Mon, 03/14/2011 - 17:07 — Emma (not verified)

Trouble with projections

Hi
I've used the above instructions to try and change my projection from WGS84 to British National Grid and get a 'dest projection error'. Is there something obvious I'm doing wrong?

I use the following output from the site to populate the 'to' section-

+proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 +x_0=400000 +y_0=-100000 +ellps=airy +datum=OSGB36 +units=m +no_defs

the 'from' is already populated with

+proj=longlat +datum=WGS84

Any help would be great as I'm quite new to DIVA and used to more automated systems such as MMG3 and Active.
Thanks

Mon, 03/28/2011 - 22:24 — Anonymous (not verified)

Actually, the program used in the background is probably cs2cs (Frank Warnerdam's extension), not proj. The original proj command does not support datum conversions. Both programs are included in the Proj4 distribution.

Anyway, the parameters seem to be correct. No errors reported from command line test, using an external Proj4 installation:

cs2cs +proj=longlat +datum=WGS84 +to +proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 +x_0=400000 +y_0=-100000 +ellps=airy +datum=OSGB36 +units=m +no_defs

So, is something, e.g. datum definition for OSGB36, missing, from DIVA?

DIVA-GIS

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