3

I want to add latitude and longitude column and their values in decimal degrees to my shapefile (fishnet). How to use ArcPy for that?

I have added lat and long using arcpy.AddGeometryAttributes_management but the unit I need is degree decimal and I got it in meters. My code is as below:

arcpy.AddGeometryAttributes_management("fish_lyr","CENTROID")

When specifying degree decimal:

arcpy.AddGeometryAttributes_management("fish_lyr","CENTROID","DEGREEDECIMALS")

it gives the following error:

ExecuteError: Failed to execute. Parameters are not valid.
ERROR 000800: The value is not a member of FEET_US | METERS | KILOMETERS | MILES_US | NAUTICAL_MILES | YARDS.
Failed to execute (AddGeometryAttributes).
0
5

You can use the da.UpdateCursor with the SHAPE@ token:

import arcpy

fc = r'C:\Test\Buildings.shp'
latfield = 'lat'
longfield = 'long'

with arcpy.da.UpdateCursor(fc,['SHAPE@',latfield,longfield]) as cursor:
    for row in cursor:
        a = arcpy.PointGeometry(row[0].centroid, arcpy.Describe(fc).spatialReference)
        b = a.projectAs(arcpy.SpatialReference(4326)).centroid
        row[1], row[2] = b.Y, b.X
        cursor.updateRow(row)
-1

In the case where the OP or a future reader can use geopandas instead of arcpy, you would do the following:

shp = 'C:/users/gis/data/fish.shp'
gdf = geopandas.read_file(shp)
(
    gdf.to_crs({'init': 'epsg:4326'}
        .assign(lon=lambda df: df['geometry'].centroid.x)
        .assign(lat=lambda df: df['geometry'].centroid.y)
        .to_crs(gdf.crs) 
        .to_file(shp)
)
3
  • @BERA I forgot to add the coordinate conversion. But I'm well aware that the OP wanted arcpy. If you read initial the premise of my answer, you'll see that I clearly acknowledged that. However, this could be a case of an X-Y problem for a different reader in the future, which case geopandas could make their life much easier. – Paul H Mar 19 '19 at 14:47
  • In epsg:4326 the first axis (x) is lat, though – nmtoken Mar 19 '19 at 16:39
  • @mmtoken, With geopandas/shapely, that order doesn't matter. Latitude, then longitude may be how we say these values, but latitude is still the y-direction. When I do this with a shape file near Portland, OR, USA, I get longitude values around -122.75 and latitude values around 45.57, which is what I expect. – Paul H Mar 19 '19 at 17:32

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