[GIS] Is it possible to change spatial reference (and reproject) feature classes in-place, using ArcMap/GeoProcessing

arcgis-desktoparcmapcoordinate systemgeoprocessing

We have an Esri based system in production; a complicated data model with a large number of feature classes. We need to migrate the data to another spatial reference.

The feature classes have class extensions and relationship classes defined on them, so the behaviour of creating new feature classes for the reprojection result that the standard projection geoprocessing tool exhibits is very cumbersome (class extensions and relationships are lost).

If necessary, we'll code up a solution but would prefer not to. Is it somehow possible, using standard or 3rd party extensions, to do a bulk, in-place reprojection and setting of new spatial reference?

Best Answer

The answer will depend on your class extensions. In reply to George's Answer you have mentioned that

as the geometry will be projected back to the projection set on the feature class when persisted after the change

This leads me to believe that your custom class extension is validating the geometry and checking the spatial reference as well.

Related Solutions

[GIS] Checking if two feature classes have same spatial reference using ArcPy

Judging from comments, you might have it already :)

You could compare the Well-Known Text (WKT) descriptions of the spatial references.

sr1 = arcpy.Describe(dataset1).spatialReference
sr2 = arcpy.Describe(dataset2).spatialReference
sr1String = sr1.exportToString()
sr2String = sr2.exportToString()

matching = False

if sr1String == sr2String:
    # Exact string match
    matching = True
else:
    # difference
    pass

[GIS] Understanding unknown spatial reference warning in ArcMap

ArcMap (and ArcGIS Pro's map and scene) can change a data layer's coordinates in-memory or "on-the-fly."

A data layer that has no coordinate reference system / spatial reference cannot be projected on-the-fly. The layer's coordinates will just be displayed as they exist. No assumption is made on what the coordinate reference system might be.

If a data layer with no coordinate system is added to ArcMap as the first layer, the data frame itself will have no coordinate system and you will find that the map scale control is grayed out, and some features of the measure tool don't work, etc.

As several people commented, if the data layer with no coordinate reference system does line up with other data layers, it probably has the same coordinate reference system as the data frame's. Where this can get tricky is that the data could be in a similar geographic coordinate reference system (datum) but not exactly the same as the data frame's. For instance NAD 1983 (2011) versus any of the earlier. If you're not comparing against very accurate imagery (sub-meter) or very specific features that are common to both layers, you won't be able to determine beyond a doubt the exact geographic coordinate reference system.

If you're reasonably certain that the coordinate reference system of the 'unknown' data layer is the same as the data frame's, use the Define Projection tool or the data layer's property page in ArcCatalog to set the coordinate reference system.

Note: coordinate reference system is an ISO term; Esri uses coordinate system. ISO's coordinate system has a different meaning than how Esri is using it.

Disclosure: I work for Esri.

Best Answer

Related Solutions

[GIS] Checking if two feature classes have same spatial reference using ArcPy

[GIS] Understanding unknown spatial reference warning in ArcMap

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