topic Re: Help in segmenting a polyline layer into equally length segments in Python Questions

Help in segmenting a polyline layer into equally length segments

RoderickPerendy — Thu, 18 Mar 2021 21:35:57 GMT

Hello, I have a script that my intentions are for it to segment polylines into equal intervals with the last polyline as a remainder. Initially, I attempted to conduct this through GeneratePointsAlongLines at equal distance and then SplitLinesAtPoint functions but noticed that this produced segmented lines that had lengths that were inconsistent with the required length. Furthermore, I'm the only person at my company that has an Advanced Pro license and I would like to make this tool work for others.

My script is able to successfully iterate through the source polylines layer and add information to an output layer using cursors and segmentAlongLine method. Though the attributes table has the correct number of rows, the feature layer still only shows the original polyline when selected. I believe what is happening is that the segmented polyline doesn't actually exist. Any ideas on what I'm doing wrong? Thank You!
Below is my script:

import arcpy
arcpy.env.overwriteOutput = True
arcpy.env.workspace = r"C:\Users\roder\OneDrive\Documents\ArcGIS\Projects\PythonScripting\PythonScripting.gdb" # Change to getParameter
polylines = "CranePath_OnRoad"#Change to getParameter
spatial_ref = arcpy.Describe(polylines).spatialReference
output = "CranePath_OnRoad_Segmented" #Change to getParameter
interval_dist = 20 # feet, Change to get Parameter
#distance_interval_unit = getParameter
arcpy.AddField_management(polylines,"Line_Length","DOUBLE")
arcpy.management.CalculateGeometryAttributes(polylines, "Line_Length LENGTH_GEODESIC", "FEET_US")
mem_polyline = arcpy.CreateFeatureclass_management("in_memory", "mem_polyline", "POLYLINE", polylines, "DISABLED", "DISABLED", spatial_ref)
arcpy.AddField_management(mem_polyline,"LineID","LONG")
in_flds = ["OID@", "SHAPE@", "Line_Length"]
out_flds = ["SHAPE@", "Line_Length", "LineID"]
cnt_in = 0
cnt_out = 0
with arcpy.da.InsertCursor(mem_polyline,out_flds) as curs_out:
with arcpy.da.SearchCursor(polylines,in_flds) as curs_in:
for row_in in curs_in:
cnt_in += 1
polyline_in = row_in[1]
from_dist = 0
lineID = row_in[0]
max_dist = float(row_in[2])
if cnt_in % 100 == 0:
print("Processing line: {}, generated {} segments".format(cnt_in, cnt_out))

while from_dist <= max_dist:
cnt_out += 1
to_dist = from_dist + interval_dist
remainder_dist = max_dist - from_dist
segment = polyline_in.segmentAlongLine(from_dist,to_dist,False)
lst_out = list((segment,interval_dist,lineID))
curs_out.insertRow(lst_out)
from_dist += interval_dist
else:
cnt_out += 1
segment = polyline_in.segmentAlongLine(from_dist-interval_dist,max_dist,False)
lst_out = list((segment,remainder_dist,lineID))
curs_out.insertRow(lst_out)

mem_polyline_fl = arcpy.MakeFeatureLayer_management(mem_polyline, "Polylines_memory")
arcpy.CopyFeatures_management(mem_polyline_fl, output)
arcpy.Delete_management(mem_polyline)
arcpy.Delete_management(mem_polyline_fl)

Re: Help in segmenting a polyline layer into equally length segments

DanPatterson — Thu, 18 Mar 2021 22:11:03 GMT

Code formatting ... the Community Version - Esri Community

would help for code readability

Re: Help in segmenting a polyline layer into equally length segments

RoderickPerendy — Thu, 18 Mar 2021 23:00:45 GMT

import arcpy arcpy.env.overwriteOutput = True arcpy.env.workspace = r"C:\Users\roder\OneDrive\Documents\ArcGIS\Projects\PythonScripting\PythonScripting.gdb" # Change to getParameter polylines = "CranePath_OnRoad"#Change to getParameter spatial_ref = arcpy.Describe(polylines).spatialReference output = "CranePath_OnRoad_Segmented" #Change to getParameter interval_dist = 20 # feet, Change to get Parameter #distance_interval_unit = getParameter arcpy.AddField_management(polylines,"Line_Length","DOUBLE") arcpy.management.CalculateGeometryAttributes(polylines, "Line_Length LENGTH_GEODESIC", "FEET_US") mem_polyline = arcpy.CreateFeatureclass_management("in_memory", "mem_polyline", "POLYLINE", polylines, "DISABLED", "DISABLED", spatial_ref) arcpy.AddField_management(mem_polyline,"LineID","LONG") in_flds = ["OID@", "SHAPE@", "Line_Length"] out_flds = ["SHAPE@", "Line_Length", "LineID"] cnt_in = 0 cnt_out = 0 with arcpy.da.InsertCursor(mem_polyline,out_flds) as curs_out: with arcpy.da.SearchCursor(polylines,in_flds) as curs_in: for row_in in curs_in: cnt_in += 1 polyline_in = row_in[1] from_dist = 0 lineID = row_in[0] max_dist = float(row_in[2]) if cnt_in % 100 == 0: print("Processing line: {}, generated {} segments".format(cnt_in, cnt_out)) while from_dist <= max_dist: cnt_out += 1 to_dist = from_dist + interval_dist remainder_dist = max_dist - from_dist segment = polyline_in.segmentAlongLine(from_dist,to_dist,False) lst_out = list((segment,interval_dist,lineID)) curs_out.insertRow(lst_out) from_dist += interval_dist else: cnt_out += 1 segment = polyline_in.segmentAlongLine(from_dist-interval_dist,max_dist,False) lst_out = list((segment,remainder_dist,lineID)) curs_out.insertRow(lst_out) mem_polyline_fl = arcpy.MakeFeatureLayer_management(mem_polyline, "Polylines_memory") arcpy.CopyFeatures_management(mem_polyline_fl, output) arcpy.Delete_management(mem_polyline) arcpy.Delete_management(mem_polyline_fl)

Re: Help in segmenting a polyline layer into equally length segments

Anonymous User — Fri, 19 Mar 2021 12:18:13 GMT

Have to ask... is that layer turned on as selectable in the TOC? Have you stepped through it with a debugger and checked out your values you are getting before being inserted?

If you are also turning this script into a tool, you can use a little conditional to assign a default value while running it as a standalone script so you don't have to keep converting polylines from polylines = getParamter() and polylines = 'CranePath_OnRoad'

polylines = GetParameter(1) if polylines == '#' or not polylines: polylines = "CranePath_OnRoad" # defaults to the set variable for standalone script operation since getParameter returns a hash when it is not set.

Re: Help in segmenting a polyline layer into equally length segments

RoderickPerendy — Fri, 19 Mar 2021 02:18:15 GMT

Hello Jeff,

Yes the source layer is selectable in the TOC. I reran the script with a fresh source to make sure. Interesting enough after the script is the run the source layer is removed from the map visually but still exists under the TOC and Catalog panes with appropriate check boxes turned on. Also thankyou for the tip and will introduce it once I get this script working correctly.

Roderick

Re: Help in segmenting a polyline layer into equally length segments

RoderickPerendy — Fri, 19 Mar 2021 02:31:40 GMT

the only debugging that I've done is set a print statement for the 'lst_out' list. Here is a snippet of it:

Re: Help in segmenting a polyline layer into equally length segments

Anonymous User — Fri, 19 Mar 2021 11:49:14 GMT

Cool, sorry, had to ask... Looking at your code, check your parameters in the calculate function:

arcpy.management.CalculateGeometryAttributes(polylines, "Line_Length LENGTH_GEODESIC", "FEET_US")

The docs show it takes a list for the geometry_property parameter like:

arcpy.CalculateGeometryAttributes_management(polylines, ["Line_Length", "LENGTH_GEODESIC"], "FEET_US")

Another thing that might be an issue is not converting the values to float for the segmentAlongLine method.

segment = polyline_in.segmentAlongLine(float(from_dist), float(to_dist), False)

Re: Help in segmenting a polyline layer into equally length segments

Anonymous User — Fri, 19 Mar 2021 12:04:11 GMT

Taking another look at the code, I am curious about the two and have always wanted to ask why ESRI puts arcpy.management.CalculateGeometryAttributes in the documents above the parameter table but always uses the style we know arcpy.CalculateGeometryAttributes_management in the examples. I think it is confusing to people. I have copied that line above the parameter table a few times when they came out with it thinking that is the syntax but the scripts threw not found exceptions.

arcpy.management.CalculateGeometryAttributes()

The example shows:

arcpy.CalculateGeometryAttributes_management()

I fixed that in my post above- and I do wonder how it ran on yours without throwing an error.

Re: Help in segmenting a polyline layer into equally length segments

RoderickPerendy — Fri, 19 Mar 2021 12:28:10 GMT

Hello Jeff,

I attempted to use the calculate geometry as listed in the API Reference document but couldn't get it to run and got the same error as when trying to run your code. However, what I did was run the calculate Geometry from GUI window and looked at the history detail. From there I was given the code I used, but I agree I wish there weren't two formats for the same function.

--------------------------------------------------------------------------- ExecuteError Traceback (most recent call last) In [21]: Line 10: arcpy.CalculateGeometryAttributes_management(polylines, ["Line_Length", "LENGTH_GEODESIC"], "FEET_US") File C:\Program Files\ArcGIS\Pro\Resources\ArcPy\arcpy\management.py, in CalculateGeometryAttributes: Line 3820: raise e File C:\Program Files\ArcGIS\Pro\Resources\ArcPy\arcpy\management.py, in CalculateGeometryAttributes: Line 3817: retval = convertArcObjectToPythonObject(gp.CalculateGeometryAttributes_management(*gp_fixargs((in_features, geometry_property, length_unit, area_unit, coordinate_system, coordinate_format), True))) File C:\Program Files\ArcGIS\Pro\Resources\ArcPy\arcpy\geoprocessing\_base.py, in <lambda>: Line 511: return lambda *args: val(*gp_fixargs(args, True)) ExecuteError: Traceback (most recent call last): File "c:\program files\arcgis\pro\Resources\ArcToolbox\scripts\calculategeometry.py", line 269, in <module> CalculateGeometry(fc, properties, lUnit, aUnit, cs, cformat) File "c:\program files\arcgis\pro\Resources\ArcToolbox\scripts\calculategeometry.py", line 101, in CalculateGeometry for row in ucur: RuntimeError: Cannot find field 'LENGTH_GEODESIC' Failed to execute (CalculateGeometryAttributes).

Re: Help in segmenting a polyline layer into equally length segments

RoderickPerendy — Fri, 19 Mar 2021 12:35:18 GMT

Hey Jeff, I do really appreciate the help on this. I attempted to add float into the segment function but resulted in same output.

Re: Help in segmenting a polyline layer into equally length segments

Anonymous User — Fri, 19 Mar 2021 12:41:39 GMT

That error says its not finding the 'Length Geodesic' field, which can be added by using the AddGeometryAttributes method

arcpy.AddGeometryAttributes_management(in_features, properties, length_unit, area_unit, coordinate_system)

Re: Help in segmenting a polyline layer into equally length segments

Anonymous User — Fri, 19 Mar 2021 13:32:53 GMT

I took your code and did some testing and I got the Attribute 'isLicensed' error when running it in 3.6. I changed to 2.7 and got it to run and produce segments. One issue was it needed to create the field 'LENGTH_GEODESIC' but that is too long so it was truncating the name to 'LENGTH_GEO'. Using 'LENGTH_GEO' instead of Line_Length worked.

Edited: I made some changes and it worked in 3.6 without the attribute error, and just using AddGeometryAttributes_management. Updated the code below-

# ------------------------------------------------------------------------------ # setup input parameters and variables arcpy.env.workspace = arcpy.GetParameter(0) if arcpy.env.workspace == '#' or not arcpy.env.workspace: arcpy.env.workspace = r"C:\Users\...\PythonTests\PythonTests.gdb" polylines = arcpy.GetParameter(1) if polylines == '#' or not polylines: polylines = "driveway" spatial_ref = arcpy.Describe(polylines).spatialReference output = arcpy.GetParameter(2) if output == '#' or not output: output = "driveway_Segmented" interval_dist = arcpy.GetParameter(3) if interval_dist == '#' or not interval_dist: interval_dist = 20 #distance_interval_unit = getParameter # ------------------------------------------------------------------------------ def insertSegment(insertList): with arcpy.da.InsertCursor(outFC, ["SHAPE@", "Line_Length", "LineID"]) as icur: icur.insertRow(insertList) def createOutputFeatureClass(): spatial_ref = arcpy.Describe(polylines).spatialReference mem_polyline = arcpy.CreateFeatureclass_management("in_memory", "mem_polyline", "POLYLINE", polylines, "DISABLED", "DISABLED", spatial_ref) arcpy.AddField_management(mem_polyline, "LineID", "LONG") return mem_polyline def createTempPolyLines(): polylineTemp = arcpy.MakeFeatureLayer_management(polylines, 'tempLyr') arcpy.AddField_management(polylineTemp, "Line_Length", "DOUBLE") arcpy.AddGeometryAttributes_management(polylineTemp, "LENGTH_GEODESIC", 'FEET_US', '', spatial_ref) return polylineTemp def createSegments(outFC, polylineTemp): with arcpy.da.SearchCursor(polylineTemp, ["OBJECTID", "SHAPE@", "LENGTH_GEO"]) as scur: for srow in scur: cnt_out = 0 polyline_in = srow[1] #shape@ from_dist = 0 lineID = srow[0] #OID max_dist = float(srow[2]) #Line_Length remainder_dist = '' while from_dist <= max_dist: cnt_out += 1 to_dist = from_dist + interval_dist remainder_dist = max_dist - from_dist segment = polyline_in.segmentAlongLine(float(from_dist), float(to_dist), False) insertSegment([segment, interval_dist, lineID]) from_dist += interval_dist else: cnt_out += 1 segment = polyline_in.segmentAlongLine(float(from_dist-interval_dist), float(max_dist), False) insertSegment([segment, remainder_dist, lineID]) print("Processing line OID: {}, generated {} segments".format(srow[0], cnt_out)) arcpy.CopyFeatures_management(outFC, output) if __name__ == "__main__": outFC = createOutputFeatureClass() polylineTemp = createTempPolyLines() createSegments(outFC, polylineTemp)

Re: Help in segmenting a polyline layer into equally length segments

RoderickPerendy — Fri, 19 Mar 2021 21:20:00 GMT

Jeff,

Thank your for cleaning up my code. I had to make a few changes, naming changing "OBJECTID" to "OID@" in 'scur' and add arcpy.AddField_management(mem_polyline, "Line_Length", "DOUBLE") to createOutputFeatureClass() in order to get it to run but I'm still getting the same issues so I'm bewildered how it was able to work for you.

import arcpy arcpy.env.overwriteOutput = True # USER INPUT FIELDS arcpy.env.workspace = r"C:\Users\roder\OneDrive\Documents\ArcGIS\Projects\PythonScripting\PythonScripting.gdb" # Change to getParameter polylines = "CranePath_OnRoad"#Change to getParameter spatial_ref = arcpy.Describe(polylines).spatialReference output = "CranePath_OnRoad_Segmented" #Change to getParameter interval_dist = 20 # feet, Change to get Parameter #distance_interval_unit = getParameter def insertSegment(insertList): with arcpy.da.InsertCursor(outFC, ["SHAPE@", "Line_Length", "LineID"]) as icur: icur.insertRow(insertList) def createOutputFeatureClass(): spatial_ref = arcpy.Describe(polylines).spatialReference mem_polyline = arcpy.CreateFeatureclass_management("in_memory", "mem_polyline", "POLYLINE", polylines, "DISABLED", "DISABLED", spatial_ref) arcpy.AddField_management(mem_polyline, "LineID", "LONG") arcpy.AddField_management(mem_polyline, "Line_Length", "DOUBLE") return mem_polyline def createTempPolyLines(): polylineTemp = arcpy.MakeFeatureLayer_management(polylines, 'tempLyr') arcpy.AddField_management(polylineTemp, "Line_Length", "DOUBLE") arcpy.AddGeometryAttributes_management(polylineTemp, "LENGTH_GEODESIC", 'FEET_US', '', spatial_ref) return polylineTemp def createSegments(outFC, polylineTemp): with arcpy.da.SearchCursor(polylineTemp, ["OID@", "SHAPE@", "LENGTH_GEO"]) as scur: for srow in scur: cnt_out = 0 polyline_in = srow[1] #shape@ from_dist = 0 lineID = srow[0] #OID max_dist = float(srow[2]) #Line_Length remainder_dist = '' while from_dist <= max_dist: cnt_out += 1 to_dist = from_dist + interval_dist remainder_dist = max_dist - from_dist segment = polyline_in.segmentAlongLine(float(from_dist), float(to_dist), False) insertSegment([segment, interval_dist, lineID]) from_dist += interval_dist else: cnt_out += 1 segment = polyline_in.segmentAlongLine(float(from_dist-interval_dist), float(max_dist), False) insertSegment([segment, remainder_dist, lineID]) print("Processing line OID: {}, generated {} segments".format(srow[0], cnt_out)) arcpy.CopyFeatures_management(outFC, output) outFC = createOutputFeatureClass() polylineTemp = createTempPolyLines() createSegments(outFC, polylineTemp)

Re: Help in segmenting a polyline layer into equally length segments

Anonymous User — Fri, 19 Mar 2021 21:45:14 GMT

That is very odd. I just ran your code and it gave me the desired output like before. ... any updates waiting to be installed?

Re: Help in segmenting a polyline layer into equally length segments

RoderickPerendy — Fri, 19 Mar 2021 22:01:27 GMT

It looks as though I'm up to date:

Guess I'll have to reach out to Esri and report on a bug.

Re: Help in segmenting a polyline layer into equally length segments

Anonymous User — Mon, 22 Mar 2021 17:59:44 GMT

Here is the script that I put together to work with the data. I think the key is projecting it from WGS84 to stateplane, and deleting the full line that is getting inserted somewhere by selecting by attributes and toasting anything over 21.

# ------------------------------------------------------------------------------ # setup input parameters and variables arcpy.env.workspace = arcpy.GetParameter(0) if arcpy.env.workspace == '#' or not arcpy.env.workspace: arcpy.env.workspace = r"C:\Users\klingj\Documents\ArcGIS\Cranewalk - On Road.gdb" polylines = arcpy.GetParameter(1) if polylines == '#' or not polylines: polylines = r"Polylines_Project" # for the stateplane projection . spatialref = arcpy.GetParameter(1) if spatialref == '#' or not spatialref: spatialref = r"Polylines_Project" spatial_ref = arcpy.Describe(spatialref).spatialReference outFC = arcpy.GetParameter(2) if outFC == '#' or not outFC: outFC = "cranePath_Seg" interval_dist = arcpy.GetParameter(3) if interval_dist == '#' or not interval_dist: interval_dist = 20 #distance_interval_unit = getParameter # ------------------------------------------------------------------------------ def insertSegment(insertList, output): with arcpy.da.InsertCursor(output, ["SHAPE@", "Line_Length", "LineID"]) as icur: icur.insertRow(insertList) def createOutputFeatureClass(): mem_polyline = arcpy.CreateFeatureclass_management('memory', "cranePath_Seg", "POLYLINE", polylines, "DISABLED", "DISABLED", spatial_ref) arcpy.AddField_management(mem_polyline, "LineID", "LONG") return mem_polyline def createTempPolyLines(): # project data here to stateplane polylineTemp = arcpy.MakeFeatureLayer_management(polylines, 'tempLyr') arcpy.AddField_management(polylineTemp, "Line_Length", "DOUBLE") arcpy.AddGeometryAttributes_management(polylineTemp, "LENGTH_GEODESIC", 'FEET_US', '', spatial_ref) return polylineTemp def createSegments(FCGeom, output): outFC = os.path.join(arcpy.env.workspace, 'cranePath_Seg') with arcpy.da.SearchCursor(FCGeom, ["OID@", "SHAPE@", "LENGTH_GEO"]) as scur: for srow in scur: cnt_out = 0 polyline_in = srow[1] #shape@ from_dist = 0 lineID = srow[0] #OID max_dist = float(srow[2]) #LENGTH_GEO remainder_dist = '' while from_dist <= max_dist: cnt_out += 1 to_dist = from_dist + interval_dist remainder_dist = max_dist - from_dist segment = polyline_in.segmentAlongLine(from_dist, to_dist, False) insertSegment([segment, interval_dist, lineID], output) from_dist += interval_dist else: cnt_out += 1 # print("Processing line OID: {}, segment from: {} to remainder: {}".format(srow[0], from_dist-interval_dist, remainder_dist)) segment = polyline_in.segmentAlongLine(from_dist-interval_dist, remainder_dist, False) insertSegment([segment, remainder_dist, lineID], output) print("Processing line OID: {}, generated {} segments".format(srow[0], cnt_out)) selctFeatures = arcpy.SelectLayerByAttribute_management(output, 'New_Selection', '''SHAPE_LENGTH > 21''') arcpy.DeleteFeatures_management(selctFeatures) arcpy.CopyFeatures_management(output, outFC) # project to WGS84 if __name__ == "__main__": output = createOutputFeatureClass() FCGeom = createTempPolyLines() createSegments(FCGeom, output)