topic Re: Correcting Drift in ArcGIS Pro Questions

Correcting Drift

Maps-Berlin — Wed, 15 Mar 2023 09:18:05 GMT

Hey everyone,

I am working with shapefiles which in part contain the same points but I assume due to reprojections in the past or possibly recalculations of geometries with different accuracies, those points drifted apart and i am now left with files that plot like this:

Is there any tools availible to identify and correct this drift so I can properly identify the matching points? Sadly the drift is not completely uniform across all points so simply moving all points by x/y is not an option.

Any ideas appreciated. Thanks a lot.

Re: Correcting Drift

JohannesLindner — Wed, 15 Mar 2023 10:01:56 GMT

If you have a unique id field with the same values in the wrong and correct layers, you can use a little Python script:

# parameters wrong_geometries_fc = "TestPoints" # layer name or path to the shapefile wrong_geometries_id_field = "IntegerField2" # name of the id field correct_geometries_fc = "TestPointsAGOL" correct_geometries_id_field = "IntegerField2" # read the correct geometries correct_geometries = {i: shp for i, shp in arcpy.da.SearchCursor(correct_geometries_fc, [correct_geometries_id_field, "SHAPE@"])} # iterate over the wrong geometries with arcpy.da.UpdateCursor(wrong_geometries_fc, [wrong_geometries_id_field, "SHAPE@"]) as cursor: for i, shp in cursor: # find the correct geometry and update try: correct_geometry = correct_geometries[i] cursor.updateRow([i, correct_geometry]) except KeyError: print(f"No correct geometry found for {wrong_geometries_id_field} = {i}")

Re: Correcting Drift

Maps-Berlin — Wed, 15 Mar 2023 11:18:58 GMT

Hey Johannes,

thank you for your reply. Sadly I have nothing in the Attributes to reference those two files with one another. Plus (I am guessing) this would only correct the matching points and leave all non matching points as is, the drift is affecting all points though and I was hoping to find a tool which identifies the drift based on the matching points and then applies a correction to all points. Now that I write that out I realize that I should maybe look into machine learning.