topic Create polygon / fc from map extent in Python Questions

Create polygon / fc from map extent

MatthiasAbele — Mon, 21 Nov 2011 16:22:47 GMT

Hallo,

there are several topics on different forums concerning this matter, but
I haven't found a hint how to this in ArcGIS 10.

Do you have an idea or a code snippet?

Thanx,

Matthias

Re: Create polygon / fc from map extent

JakeSkinner — Sat, 11 Dec 2021 07:46:25 GMT

Hi Matthias,

Here is a code sample. The code grabs the extent from an MXDs data frame, creates an array, and then converts the array to a polygon feature class.

import arcpy
from arcpy import env
from arcpy import mapping

env.workspace = r"C:\temp\Test.gdb"

mxd = mapping.MapDocument(r"C:\temp\python\Philadelphia.mxd")
dataframe = mapping.ListDataFrames(mxd, "*")[0]
frameExtent = dataframe.extent
XMAX = frameExtent.XMax
XMIN = frameExtent.XMin
YMAX = frameExtent.YMax
YMIN = frameExtent.YMin
pnt1 = arcpy.Point(XMIN, YMIN)
pnt2 = arcpy.Point(XMIN, YMAX)
pnt3 = arcpy.Point(XMAX, YMAX)
pnt4 = arcpy.Point(XMAX, YMIN)
array = arcpy.Array()
array.add(pnt1)
array.add(pnt2)
array.add(pnt3)
array.add(pnt4)
array.add(pnt1)
polygon = arcpy.Polygon(array)
arcpy.CopyFeatures_management(polygon, "Polygon_Extent")

Re: Create polygon / fc from map extent

MatthiasAbele — Tue, 22 Nov 2011 08:37:40 GMT

Hallo JSkinn3,

thany, the code works perfectly. Is it possible to loop through a folder, which contains several
mxds and store all polygons in one fc?

Yours,

Matthias

Re: Create polygon / fc from map extent

JakeSkinner — Wed, 23 Nov 2011 14:09:10 GMT

Take a look at this thread.

Re: Create polygon / fc from map extent

CraigPrisland1 — Thu, 10 Sep 2015 16:10:08 GMT

I have been looking for something like this for a little while now and the Python script that was posted here a few years back worked great. Thnaks for that! However, would it be possible to run something like this on multiple pages? I used Data Driven Pages to create several pages and would like a feature class or shapefile of the map extent of all of these pages. I noticed that this script will only output the first page.

Thanks in advance and I appreciate the assistance!

Re: Create polygon / fc from map extent

DarrenWiens2 — Sat, 11 Dec 2021 07:46:28 GMT

You can modify Jake Skinner's code as below to accommodate DDPs (mostly tested):

import arcpy  
from arcpy import env  
from arcpy import mapping  
  
env.workspace = r"C:\temp\Test.gdb"  

extents = []  
mxd = mapping.MapDocument(r"C:\temp\python\Philadelphia.mxd")  
for pageNum in range(1, mxd.dataDrivenPages.pageCount + 1):
     mxd.dataDrivenPages.currentPageID = pageNum
     dataframe = mapping.ListDataFrames(mxd, "*")[0]  
     frameExtent = dataframe.extent  
     XMAX = frameExtent.XMax  
     XMIN = frameExtent.XMin  
     YMAX = frameExtent.YMax  
     YMIN = frameExtent.YMin  
     pnt1 = arcpy.Point(XMIN, YMIN)  
     pnt2 = arcpy.Point(XMIN, YMAX)  
     pnt3 = arcpy.Point(XMAX, YMAX)  
     pnt4 = arcpy.Point(XMAX, YMIN)  
     array = arcpy.Array()  
     array.add(pnt1)  
     array.add(pnt2)  
     array.add(pnt3)  
     array.add(pnt4)  
     array.add(pnt1)  
     polygon = arcpy.Polygon(array) 
     extents.append(polygon)

arcpy.CopyFeatures_management(extents, "Polygon_Extent")

Re: Create polygon / fc from map extent

CraigPrisland1 — Thu, 10 Sep 2015 17:17:48 GMT

Darren,

This is exactly what I was looking for. Thank you very much!

Re: Create polygon / fc from map extent

CraigPrisland1 — Wed, 07 Oct 2015 17:02:31 GMT

Darren,

This code you modified worked well. I did have one other question if possible. The "Polygon_Extent" layer that gets outputted does not contain any fields. Is it possible to incorporate the field that was used to create the Data Driven Pages from (i.e. the index layer) into the outputted layer?

Thanks again

Re: Create polygon / fc from map extent

DarrenWiens2 — Sat, 11 Dec 2021 07:46:31 GMT

As far as I know, you have to do a fair bit of recoding to incorporate attributes into this type of snippet. It can be done by creating a new feature class and adding the field before the loop, then adding features to the feature class inside the loop using an InsertCursor.

If someone know if it's possible to include attributes somehow using CopyFeatures, I would be eternally grateful. Something like this would be ideal, although I don't believe it's possible:

  extents.append([polygon, field1, field2, etc.])
arcpy.CopyFeatures_management(extents, "Polygon_Extent")

Re: Create polygon / fc from map extent

WesMiller — Wed, 07 Oct 2015 20:08:44 GMT

You could use Spatial Join—Help | ArcGIS for Desktop

Re: Create polygon / fc from map extent

DarrenWiens2 — Wed, 07 Oct 2015 20:18:58 GMT

In most cases (mutually exclusive index features), you could use Spatial Join for this but not necessarily for more complex cases (e.g. coincident or overlapping index features).

Re: Create polygon / fc from map extent

WesMiller — Wed, 07 Oct 2015 20:32:57 GMT

I was thinking you could use Match Option HAVE_THEIR_CENTER_IN and get the desired results.

Re: Create polygon / fc from map extent

DarrenWiens2 — Wed, 07 Oct 2015 21:01:16 GMT

Yes, that would work most of the time, although some index features may not cover the center of the map extent, and the center of some map extents may cover multiple index features. Whether or not that matters would depend on why you wanted to know which feature produced which map extent, or if any would do.

Re: Create polygon / fc from map extent

CraigPrisland1 — Thu, 08 Oct 2015 12:32:31 GMT

I initially used the Spatial Join geoprocessing tool using the matching option HAVE_THEIR_CENTER_IN, however as Darren eluded to, some index features do not cover the center of the map extent while several others cover multiple index features. The CONTAINS option works similar as well, however there are several index features contained in each map extent so there will be a large amount of manual QC involved by going this route.

Re: Create polygon / fc from map extent

CraigPrisland1 — Fri, 09 Oct 2015 14:47:28 GMT

I have found a workaround to incorporate the attributes into the Polygon_Extent output from the index layer from Data Driven Pages by first sorting my map in ascending alphabetical order and then running the script. The polygons are then created in order. By using the FID field, I can then join it with the index layer when I create a temporary field in that layer and add ascending values into this field.

I did have one other question to see if this is feasible. My map pages have an engineering scale tied to each page (i.e 1" = 210') using the following expression in the text:

SCALE: 1" = <dyn type="dataFrame" name="DataFrameName"

property="scale" pageUnits="in" mapUnits="ft" pageValue="1"

decimalPlaces="0"/>'

Would it be possible to get this value into the Polygon_Extent output file as well?

Thanks again for your assistance.

Re: Create polygon / fc from map extent

DarrenWiens2 — Sat, 11 Dec 2021 07:46:33 GMT

I believe you can grab the scale inside the loop, once you've got your dataframe object, using:

scale = dataframe.scale

This will return an absolute scale for the dataframe, like 5000 would equal a scale of 1:5000. You could then do some math to calculate how many feet would equal one inch. For example:

scale = dataframe.scale # e.g. 5000
engScale = '1 inch = ' + int(scale/12) + ' feet' # returns "1 inch = 417 feet"

You can escape quotes inside the string, but that's an extra step for me.

Re: Create polygon / fc from map extent

AmbroseClarke — Wed, 21 Nov 2018 14:43:48 GMT

Old thread I know - but there is now an easy way in case anyone searching...

arcpy.Extent has a polygon property that neatly returns the extent as a polygon

ex  = extent.polygon‍‍