topic Change linear unit of spatial reference for geometry in cursors? in Python Questions

Change linear unit of spatial reference for geometry in cursors?

ZachLiu1 — Mon, 09 Dec 2013 22:21:55 GMT

Hi, I want to change the spatial reference linear unit for geometry calculations.

I know you can pass the sr object in cursor, so I tried this:

I read from the document that linearUnitName is both readable and writable.

sr = arcpy.Describe(inLine).spatialReference sr.linearUnitName = "Foot" cursor = arcpy.da.SearchCursor(fc, ["SHAPE@"], "", sr)

but it looks not working.

Could anyone help?:D

I am trying to find points along polylines based on distance, so I need the distance in another unit.

What else could I do?

Re: Change linear unit of spatial reference for geometry in cursors?

ShaunWalbridge — Sat, 11 Dec 2021 20:09:58 GMT

cursor = arcpy.da.SearchCursor(fc, ["SHAPE@"], "", sr)

There are two separate SearchCursors, the top-level one, and the one within the data access module. The data access module one that you're using above is designed for performance, and in doing so loses some of the flexibility of the top-level one. Try changing the call to:

desc = arcpy.Describe(inLine)
sr = desc.spatialReference
sr.linearUnitName = "Foot"
shapefieldname = desc.ShapeFieldName

rows = arcpy.SearchCursor(fc, "", sr)

for row in rows:
    feat = row.getValue(shapefieldname) # this feature should be reprojected.
    # do further manipulations as needed with the feat

That should work, and the documentation for arcpy.SearchCursor states "spatial_reference: When specified, features will be projected on the fly using the spatial_reference provided.".

cheers,
Shaun

Re: Change linear unit of spatial reference for geometry in cursors?

ZachLiu — Sat, 11 Dec 2021 20:10:00 GMT

Thanks for help. It is still not working for some reason.
I tried to test if I can change the linearUnitName of the spatial reference by

 sr = desc.spatialReference
 sr.linearUnitName = "Meter"
 print sr.linearUnitName

but it is not changed at all.

Re: Change linear unit of spatial reference for geometry in cursors?

ZachLiu1 — Tue, 10 Dec 2013 13:36:27 GMT

All right, thanks to the post on Arcpy Cafe, I figured this out.

http://arcpy.wordpress.com/tag/spatialreference/

It looks like changing sr.linearUnitName doesn't change the spatial unit,

but this solution works!