Locate SRIDs in the database system to ensure they match after migration

Summary

An SRID, or Spatial Reference Identifier, is an identifier that gets generated in a Relational Database Management System (RDBMS) and is associated with a unique coordinate system.

In most cases, the SRID shows up as the EPSG code and is stored within the geometry of the feature class in a database. The screenshot below shows the results of querying the SRID in an Enterprise Geodatabase inside SQL Server Management Studio: 

In the image above:

• 3857 is the ESPG code for the default coordinate system that feature classes in ArcGIS Pro are created in, Web Mercator.
• https://epsg.io/3857

After running the Project tool on this feature class and setting it to NAD 1927 StatePlane California, we can see that the newly projected feature class shows up with a different SRID in SQL Server Management Studio, as shown in the next image:

• 26741 is the EPSG code for NAD27 / California zone I.
• https://epsg.io/26741

Cause

SRIDs are good to keep in mind because, if they do not match when migrating databases, the user may run into errors when executing processes such as Data Pump in Oracle. 

Sometimes, if the RDBS does not recognize the coordinate system, such as in the case where a custom geographic transformation was used, it creates a custom SRID that is not associated with a EPSG code. This can get confusing because, even if the data shows up as Web Mercator in ArcGIS Pro, it may show up with a different SRID when queried in the database. 

Procedure

To verify whether the SRIDs of two feature classes match, we can first check their projections in ArcGIS Pro by right-clicking the  feature class in the Enterprise Geodatabase and navigating to Properties > Spatial Reference, as shown in the next image:

• If checking here shows that the spatial reference is the same in on the ArcGIS Pro side, we can run queries in the RDBMS to check the SRID. Here is an example of the query we would use to find the SRID of a feature class in SQL Server Management Studio:

SELECT TOP 1 shape.STSrid AS SRID
FROM SchemaName.FeatureClassName;

If the SRIDs do not match and errors are occurring due to an unrecognized projection, the following workaround can be implemented to "reset" the SRID in the database so it reads it properly:

1. Copy the feature class to new feature class in same database.
2. Rename the original feature class.
3. Define projection of the copied feature class.
4. Rename the copied feature class to what the original feature class name was.
5. The database should now recognize projection.