Resolving an unrecognized Esri Coordinate System Exception

FME and Esri Coordinate Systems

FME maintains a list of naming associations between Esri and FME coordinate systems in an exceptions file at FME_HOME\Reproject\Exceptions\esriwkt.db.

Exceptions are a list of coordinate system naming associations that match FME coordinate systems to their Esri equivalents.

Unrecognized Coordinate Systems

Sometimes FME encounters an Esri coordinate system it does not recognize, and sometimes ArcGIS encounters an FME-generated coordinate system it does not recognize. When this happens you can:

• Check the exceptions file to see if the coordinate system is properly defined there.
• Upgrade your version of FME. You may find that older versions don’t contain all the up-to-date coordinate system definitions for Esri.
• Contact Safe's support team so that we can check if we have the latest definitions from Esri.
• Add the required information yourself to an exceptions file.

Adding a New Exception

For Esri coordinate systems that FME does not know about, you can add your own Esri - FME coordinate system association in a file called MyExceptions.db, located in the same directory as esriwkt.db. Keeping a separate exceptions file will make it easier to maintain your own exceptions independent of FME upgrades. Steps:

1. View the source Esri data in the FME Data Inspector. Select any feature, then click on the coordinate system in the Feature Information panel (which will likely be named FME_0 since no match was found). In the description copy the value of the ESRI_WKT string.
2. Create or edit a file called MyExceptions.db in the same directory as esriwkt.db.
3. Add a line to name the new coordinate system: ESRI|<fme coordinate system name>|
4. At the end of the line paste the ESRI_WKT string from the FME Data Inspector and save.

You should end up with an entry that looks like this example:

 ESRI|LL84|GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137,298.257223563]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]]

Considerations

• You may need to double check the Esri coordinate system list from within ArcGIS to make sure you have the right association.
• The exceptions association is done as an exact string match, so decimals and capitals will make a difference. e.g. 1 != 1.0.
• You can also get the ESRI_WKT from the .PRJ component of a shapefile, although there may be slight differences and you may need to try both. Make sure you change all whole numbers to decimals as .PRJ typically stores zero as '0' whereas FME will usually require a 0.0.
• Remember you can have multiple entries or associations for a particular FME coordinate system, but the first one encountered is the one that will be used for writing.
• If you still have trouble, try creating a shapefile or geodatabase file with the appropriate coordinate system from within ArcGIS, and then use the FME Data Inspector to read the ESRI_WKT from the Esri-generated file. A file created by ArcGIS explicitly sets the ESRI_WKT, whereas a file created from an FME translation to an Esri format using a custom coordinate system may have a slightly different ESRI_WKT.

Testing the New Exception

Its a good idea to thoroughly test your new coordinate system referencing as follows:

1. Try reading existing data with FME, and make sure it is now correctly recognized.
2. Write out the same data with the projection set to be the same as the source.
3. Read the data you just exported with FME to make sure it can read its own data you just generated.
4. Make sure you can read and recognize the new FME generated data with ArcCatalog.
5. Make sure data modified or created by ArcGIS can be recognized by the FME Data Inspector.