I want to determine the coordinates of my current data frame. To do so I wrote this script:

def DataFrame ():

  mxd = arcpy.mapping.MapDocument("CURRENT") 
  df = arcpy.mapping.ListDataFrames(mxd,"Layers")[0]
  return mxd,df

def Center (df):

  extent = df.extent 
  xmin = extent.XMin
  xmax = extent.XMax
  ymin = extent.YMin
  ymax = extent.YMax

  x = xmax - ((xmax - xmin)/2)
  y = ymax - ((ymax - ymin)/2)
  return x,y

As long as I am working with a geographic coordinate system, the results will be exactly the longitude and latitude. But as soon as I have a projected coordinate system it will return map units (i.e. meters). How can I avoid that problem? I always need to get lon/lat independend on the maps projection.

  • 1
    Have you looked at the Convert Coordinate Notation tool? – PolyGeo Aug 9 '13 at 9:56
  • Hmm, as far as I understand it right, this would mean that I have to create tables for the values that can then be converted. I was hoping that there is a much easier way like just using "arcpy.convertCoordinates" or something. – Gideon Aug 9 '13 at 10:07

Try using the projectAs function available on your Extent object:

extent_geographic = df.extent.projectAs(arcpy.SpatialReference(4326)) # GCS_WGS_1984
  • That was exactly what I was looking for. Thank you very much! Works perfectly. – Gideon Aug 9 '13 at 11:05
  • I thought there was an easier way. – PolyGeo Aug 9 '13 at 12:13
  • Ok, now I am feeling dumb. When I tried it some hours ago, it worked in my script and also in the python window. Now I tried again and suddenly I get the Error message: "Runtime error <type 'exceptions.AttributeError'>: 'Extent' object has no attribute 'projectAs'". – Gideon Aug 9 '13 at 13:19
  • That's strange. See if you can reproduce it and send it to ESRI as a bug report. I would get a different error if I tried to use arcpy.SpatialReference("GCS_WGS_1984") -- for some reason it didn't like that but the SRID worked fine. – blah238 Aug 9 '13 at 17:11

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