[Proj] Clarke 1866

Melita Kennedy mkennedy2 at earthlink.net
Fri Mar 10 19:29:19 EST 2006

In ArcInfo workstation which includes the ESRI coverage, GRID, and TIN 
data formats, if you don't explicitly use the DATUM keyword when defining
the coordinate system, the default spheroid is Clarke 1866. 

ArcGIS (desktop) which uses the projection engine library, requires a 'full' 
geographic coordinate system definition. Faced with a definition that only 
has "Spheroid Clarke1866", we expand it out into "GCS_Clarke_1866". 
There aren't any geographic/datum transformations for it of course.

If I see data with GCS_Clarke_1866, I know it was probably a coverage 
or a GRID at some point in its life. 


Melita Kennedy
ESRI Product Specialist
mkennedy at esri.com

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