ArcPy – Calculating XY Coordinates in Decimal Degrees from Projected Datasets

arcgis-10.0arcpycursormodelbuilder

Is it possible to calculate points XY coordinates in Decimal Degrees in model or script when a feature class is in projected coordinate system?

It's easy when a FC is in geographic coordinate system:

using Add XY Coordinates tool or
using Python expression eg. !shape.extent.XMax!

I've found that area and length properties of geometry field can be modified with geometry unit conversion keyword. For linear units of measue one can use @DECIMALDEGREES.
Unfortunatelly, !shape.extent.XMax@decimaldegrees! doesn't work as XMax is not a length.

In Calculate Geometry function (accessed from right-click) there's a possibility to choose Decimal Degrees output type even for projected feature class.
Can I do this using ArcPy?

Here's a code snippet based on iRfAn's solution:

import arcpy, os
projectedFC = r"C:\tmp\test.gdb\points01_Projected"
prjFile = os.path.join(arcpy.GetInstallInfo()["InstallDir"],
            r"Coordinate Systems\Geographic Coordinate Systems\World\WGS 1984.prj")
spatialRef = arcpy.SpatialReference(prjFile)

updCursor = arcpy.UpdateCursor(projectedFC,"", spatialRef)
for row in updCursor:
    pnt = row.Shape.getPart(0)
    row.X = pnt.X
    row.Y = pnt.Y
    updCursor.updateRow(row)

del updCursor, row

Best Answer

I think you can.

Just define the Spatial Reference in WGS-84 and use cursor using this Spatial Reference.

Coordinates are specified in the spatial_reference provided, and converted on the fly to the coordinate system of the dataset.

Fore more detail see this.

Related Solutions

[GIS] How to figure out the length of polyline features in a feature class with a WGS 1984 coordinate system

I thought at first the arcpy.Polyline.getLength() method would work, as you can specify a measurement type and units but it did not because it is GCS. As you can see here, we are still in Decimal Degrees:

>>> with arcpy.da.SearchCursor("line_wgs", 'SHAPE@') as rows:
...     for row in rows:
...         print row[0].getLength('PLANAR', 'METERS')
...         
0.00193201661559
>>> desc = arcpy.Describe("line_wgs")
>>> desc.spatialReference.factoryCode
4326

What you can do is add a spatial reference to your search cursor (such as the Web Mercator):

>>> with arcpy.da.SearchCursor("line_wgs", 'SHAPE@', spatial_reference=arcpy.SpatialReference(102100)) as rows:
...     for row in rows:
...         print row[0].getLength('PLANAR', 'METERS')
...         
215.071313581
>>>

Note, since WGS Web Mercator is in meters you can just use the length property as you did in your first one:

>>> with arcpy.da.SearchCursor("line_wgs", 'SHAPE@', spatial_reference=arcpy.SpatialReference(102100)) as rows:
...     for row in rows:
...         print row[0].length
...         
215.071313581
>>>

[GIS] Calling a model from a python script

You are mixing up the "pointers" to the geoprocessor object (arcpy then you create gp). You are clearly using some older code and consequently mixed up your code. Your code implies that the toolbox sits within a geodatabase so you should be using the correct path. This should work:

import arcpy
arcpy.ImportToolbox('Path of my geodatabase') # e.g. c:\temp\mygdb.gdb\myToolbox
arcpy.env.overwriteOutput = True
try:
    # Run the model
    # All arguments were supplied to model prior to saving
    arcpy.MultiLine_Geocoder() # ModelName_ToolboxAlias
except arcpy.ExecuteError:
    print(arcpy.GetMessages(2))

At this point I should point out there are always examples of how to call such functions in the help file! I suggest you get into the practice of looking at the code samples, so for calling models from within scripts you need to be reviewing the sample code for ImportToolbox. All tools\functions have code samples.

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