New ellipsoids

New ellipsoids are stored in a text file named ellips.txt that can exist either locally or in the $PROHOME/etc directory, or both. The following is the top portion of the file.

!
!       NOTE: The range of E908 to E998 is reserved for
!             local customer development.
!
!             New ellipsoid definitions can be submitted to
!             [email protected]
!
"E009","Airy 1830",6377563.396,6356256.91
"E011","Modified Airy",6377340.189,6356034.448
"E910","ATS77",6378135.0,6356750.304922
...

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:

Field No.	Example Value	Description
1	E910	A unique code for the ellipsoid that does not already exist in this file. The first character is E (or e), for ellipsoid, followed by an integer (maximum of three characters).
2	"ATS77"	A descriptor string for the Earth ellipsoid. This descriptor is not currently used in the software. An empty character string can be used.
3	6378135.0	The ellipsoid semi-major axis, in meters.
4	6356750.305	The ellipsoid semi-minor axis, in meters.

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 can be added to $PROHOME/etc/ellips.txt.

To make the definition locally available only, add it to a local copy of the file. A local copy of ellips.txt is searched before $PROHOME/etc/ellips.txt.

At the operating-system level (for example, on a UNIX platform), you can copy the files as follows:

% cp $PROHOME/etc/ellips.txt .
% chmod 644 ellips.txt

If datum shifts are involved, the datum that uses the new ellipsoid must be defined. To do this, see Defining new datums.