To add the definition once so it is globally available to all users (and if you have write-permission to the file), the new definition would be added to $PCIHOME/etc/ellips.txt.
Or the new definition may be added to a local copy of the file. (This would not be globally available to all users.) At the operating system level (on a Unix platform in this example), you could copy the files as follows:
% cp $PCIHOME/etc/ellips.txt . % chmod 644 ellips.txtNOTE: A local copy of ellips.txt will be searched before (and so has priority over) $PCIHOME/etc/ellips.txt.
To define a new ellipsoid, add the new ellipsoid definition as one line of text to the ellips.txt file. For example:
"E910","ATS77",6378135.0,6356750.305
Where the fields of the new ellipsoid record are as follows:
1. "E910" - A unique code for the ellipsoid.
This would be one that doesn't exist already
in this file. The first character would be
E (or e) for Ellipsoid followed by an integer
(maximum of 3 characters).
2. "ATS77" - A descriptor string for the earth ellipsoid.
This descriptor isn't used at present in the software
but a field is expected. An empty character string ""
could be used.
3. 6378135.0 - The ellipsoid semi-major axis in metres.
4. 6356750.305 - The ellipsoid semi-minor axis in metres.
If datum shifts are involved, the datum that uses the new ellipsoid
would have to be defined. To do this see the NEW DATUMS topic.