Some datasets may require a datum that is not predefined in FME. In such a case, a custom datum may be created. Datum definitions may occur in an FME mapping file, as well as in the FME_HOME/Reproject/MyCoordSysDefs.fme file. The syntax of a datum definition is:
DATUM_DEF <datumName> \
[DESC_NM <descriptive name>] \
[SOURCE <source>] \
ELLIPSOID <ellipsoid name> \
[USE <use type>] \
[DELTA_X <x value>] \
[DELTA_Y <y value>] \
[DELTA_Z <z value>] \
[BWSCALE <bwscale>] \
[ROT_X <rotX>] \
[ROT_Y <rotY>] \
[ROT_z <rotz>]
Examples
See examples in FME_HOME/Reproject/MyCoordSysDefs.fme. Note that at least one transformation should be added for most datums. See Adding a Custom Transformation for more details.
Datum Definition Parameters
|
Name |
Range |
Description |
Optional |
|---|---|---|---|
|
DATUM_DEF |
CS-Map identifier name, as described in FME_HOME/Reproject/LocalCoordSysDefs.fme |
The name of the datum being defined. |
No |
|
DESC_NM |
any string |
A descriptive name for the datum. |
Yes |
| SOURCE | any string | The individual or agency providing the datum parameters. | Yes |
| ELLIPSOID | valid ellipsoid | The ellipsoid upon which the datum is based. |
No |
| USE | See Datum USE Methods |
Not used in FME 2013 or later workspaces. The type of approximation used when the datum is involved in a datum conversion. |
Yes |
| DELTA_X |
Floating-point value |
Not used in FME 2013 or later workspaces. The X component of the vector from the geocenter
of the datum being defined to the geocenter of the WGS-84 datum. Units: meters. |
Yes |
| DELTA_Y | Floating-point value |
Not used in FME 2013 or later workspaces. The Y component of the vector from the geocenter of the datum being defined to the geocenter of the WGS-84 datum. Units: meters. |
Yes |
| DELTA_Z | Floating-point value |
Not used in FME 2013 or later workspaces. The Z component of the vector from the geocenter of the datum being defined to the geocenter of the WGS-84 datum. Units: meters. |
Yes |
| BWSCALE | Floating-point value |
Not used in FME 2013 or later workspaces. The scale factor employed by the BURSA use-type, in parts per million. Not used in FME 2013 or later workspaces. |
Yes |
| ROT_X | Floating-point value |
Not used in FME 2013 or later workspaces. The X rotation factor employed by the BURSA use-type. Units: Seconds of arc. |
Yes |
| ROT_Y | Floating-point value |
Not used in FME 2013 or later workspaces. The Y rotation factor employed by the BURSA use-type. Units: Seconds of arc. |
Yes |
| ROT_Z | Floating-point value |
Not used in FME 2013 or later workspaces. The Z rotation factor employed by the BURSA use-type. Units: Seconds of arc. |
Yes |