topic Re: identifying arc segments in python in Python Questions

identifying arc segments in python

danbecker — Fri, 03 Jun 2011 15:11:33 GMT

In python, how would one go about identifying feat. classes that contain arc segments?

Client's oracle system wont' load feat. classes containing arcs, and I don't have ArcInfo to run generalize command!

So, best I can do is identify feat. classes, then manually fix them in ArcMap...thanks.

Re: identifying arc segments in python

JakeSkinner — Sat, 11 Dec 2021 07:48:27 GMT

If an arc exists, it's centroid and true centroid will be different values. Therefore you can search each feature class to see if any centroids do not match the true centroids. Ex:

lstFCs = arcpy.ListFeatureClasses("*", "Polyline")

for fc in lstFCs:
    rows = arcpy.SearchCursor(fc)
    print fc
    for row in rows:
        type = row.Shape
        geom = str(type.centroid.X)
        truegeom = str(type.trueCentroid.X)
        if geom != truegeom:
            print row.ObjectID

del row, rows

This will print the feature class and the OBJECTID of any arcs within that feature class.

Re: identifying arc segments in python

danbecker — Sat, 11 Dec 2021 07:48:30 GMT

humm, created 2 polygons inside a feat. class. OBJECTID = 1 was created using the "end arc point segment tool" and OBJECTID = 2 was created using the "straight line segment" tool.

Ran this script:

fclist = gp.listfeatureclasses("arc_test*")
            for fc in fclist:
                rows = gp.searchcursor(fc)
                row = rows.next()
                while row:
                    typ = row.Shape
                    geom = str(typ.centroid.X)
                    print row.getvalue("OBJECTID"), geom
                    truegeom = str(typ.truecentroid.X)
                    print row.getvalue("OBJECTID"), truegeom
                    row = rows.next()

Here is the output:

1 -93.0638463269
1 -93.0638463269
2 -93.0635589449
2 -93.0635589449

both geom & truegeom are the same, for both polygons, even though 1 of them contains an arc segment??

Re: identifying arc segments in python

JakeSkinner — Fri, 03 Jun 2011 16:52:39 GMT

The previous code will only work for polyline feature classes. I will have to see if there is a way to do this for polygon feature classes.

Re: identifying arc segments in python

danbecker — Mon, 06 Jun 2011 12:18:49 GMT

thanks Jake.

Yeah, unfortunately, most of the feat. classes I need to check are polygons

Re: identifying arc segments in python

ToddSmith — Thu, 03 May 2012 19:24:13 GMT

This code works great if you want to identify lines that are not straight but I am not having much luck identifying true "arcs." For example, if you run this code on a pipe feature class it flags almost all of them because there are not too many that are straight. Any ideas on how to flag only the line segments that were drawn in as an end point arc segment?
Thanks,
Todd

Re: identifying arc segments in python

JakeSkinner — Sat, 11 Dec 2021 07:48:33 GMT

Truncate how many decimals are returned for the centroid and 'true' centriod. For example:

for fc in lstFCs:
    rows = arcpy.SearchCursor(fc)
    print fc
    for row in rows:
        type = row.Shape
        geom = "%.4f" % type.centroid.X
        truegeom = "%.4f" % type.trueCentroid.X
        if geom != truegeom:
            print row.ObjectID

del row, rows

This should only return your 'true' arcs.