Topic:
Where can information on datums and ellipsoids be found?

Description:
It is sometimes necessary to add a datum or ellipsoid to GeoFrame that is not
on the coordinate system or projection list for the project parameters.  There
are many sites to select from.  Is there one site that provides more information
than others?  

Solution:
On the internet, go to:
http://www.agileimage.com/html/GeoTiff.html

This site has information on eight topics associated with datums:

CTRANS - Coordinate Transformations
DATUM - Reference Datums
ELLIPS - Ellipsoids
GEOGCS - Geographic Coordinate Systems
PMERID - Prime Meridians
PROJ - Complete Cartographic Projections
PROJCS - Projected Coordinate Systems
UNITS - Angular and Linear Units
VERTCS - Vertical Coordinate Systems

This site is operated by Agile Image Movers.  Their Image Editor makes all the
Silicon Graphics ImageVision(r) operators available for image manipulation and
provides some additional additional operators.

Data is presented in a GeoTiff format that provides geographic information as
additional TIFF Tags in a normal TIFF file. The georeferencing information is
encoded within the GeoTiff keys and refers to values found in the European
Petroleum Survey Group (EPSG) tables of common cartographic projections.

The first line of each file has column headings using the EPSG names. The second
line is a short name for each field, or a reference to a field in another table.
UNITS.code refers to the code field of the UNITS table.  Hence these tables are
suitable for conversion to a spreadsheet format.

(The curent tables are available as a MicroSoft Access v7 database from EPSG.
The current tables are delimited by tabs rather than commas.)



Last Modified on: 14-SEP-00