topic Re: Removing one point from a multipoint feature class in Geoprocessing Questions

Removing one point from a multipoint feature class

JohnReiser — Sun, 12 Dec 2021 16:33:49 GMT

Hello,

I have a multipoint feature class generated from LAS to Multipoint. In the data, there are a few erroneous points I'd like to delete. The area covered ranges in elevation from 50 to 250 feet above sea level. What I figured I could do is iterate through all the points and remove any that have a Z value below 0 or above 1000.

import arcgisscripting, os, sys, re
gp = arcgisscripting.create(9.3)

if len(sys.argv)< 2:
    gp.AddError("Insufficient parameters.")
    sys.exit(2)

ifc = sys.argv[1]
des = gp.Describe(ifc)
sfn = des.ShapeFieldName
oid = des.OIDFieldName

result = gp.GetCount_management(ifc)
cnt = int(result.GetOutput(0))
gp.AddMessage("%d features in feature class." % cnt)
cursor = gp.updatecursor(ifc)
row = cursor.next()
gp.SetProgressor("step", "Iterating through Multipoints...", 0, cnt, 1)
while row:
    feat = row.GetValue(sfn)
    partnum = 0
    partcount = feat.PartCount
    while partnum < partcount:
        point = feat.GetPart(partnum)
        if((point.z > 1000) or (point.z < 0)):
            gp.AddWarning("Multipoint feature outside of threshold.")
            gp.AddMessage("%d -> %d -> %s" % (row.GetValue(oid), partnum, str(point.z)))
            feat.Remove(partnum)
#        else:    
#            gp.AddMessage(str(partnum) + "->" + str(point.z))
        partnum += 1
    gp.SetProgressorPosition()
    row = cursor.next()

The commented out section, if moved into the if((point.z > 1000) or (point.z < 0)): block will correctly identify the points outside my range. I just don't know how to remove the point in question as I iterate over the array of multipoint parts. I thought I could use the "remove" method on the feature array to remove that specific part, but "feat" does not have the remove method (ie feat.remove(partnum)). point.remove(0) doesn't work either.

Do I have to reconstruct a multipart feature, omitting any offending points and then replace the record, or is there some way to remove vertices/multipoint parts as I'm walking through?

Thanks in advance for your help.

Re: Removing one point from a multipoint feature class

FrankPerks — Sat, 11 Dec 2021 22:35:45 GMT

To remove a row within the feature class you need to use the cursor.deleterow method

e.g.:>

import arcgisscripting, os, sys, re
gp = arcgisscripting.create(9.3)

if len(sys.argv)< 2:
    gp.AddError("Insufficient parameters.")
    sys.exit(2)

ifc = sys.argv[1]
des = gp.Describe(ifc)
sfn = des.ShapeFieldName
oid = des.OIDFieldName

result = gp.GetCount_management(ifc)
cnt = int(result.GetOutput(0))
gp.AddMessage("%d features in feature class." % cnt)
cursor = gp.updatecursor(ifc)
row = cursor.next()
gp.SetProgressor("step", "Iterating through Multipoints...", 0, cnt, 1)
while row:
    feat = row.GetValue(sfn)
    partnum = 0
    partcount = feat.PartCount
    while partnum < partcount:
        point = feat.GetPart(partnum)
        if((point.z > 1000) or (point.z < 0)):
            gp.AddWarning("Multipoint feature outside of threshold.")
            gp.AddMessage("%d -> %d -> %s" % (row.GetValue(oid), partnum, str(point.z)))
            # To remove you must use updatecursor.deleterow(<row>)
            cursor.deleterow(row)
            # ^^^^^^^^^^^^^^
            ###feat.Remove(partnum)
#        else:    
#            gp.AddMessage(str(partnum) + "->" + str(point.z))
        partnum += 1
    gp.SetProgressorPosition()
    row = cursor.next()

Re: Removing one point from a multipoint feature class

JohnReiser — Wed, 20 Oct 2010 11:31:10 GMT

That wil remove one record from the feature class. Each record has 3500 LIDAR returns, so removing one record is overkill to rid myself of one erroneous return. I have a few bad returns and they not all within the same record, so removing whole records will leave gaps in my terrain. I need to remove one point within the set of 3500 stored in one record. Multipart to singlepart is not a viable option, as it makes the file sizes increase considerably.

Thanks.

Re: Removing one point from a multipoint feature class

LoganPugh — Sat, 11 Dec 2021 22:35:47 GMT

This seems to work for me:

import arcgisscripting

gp = arcgisscripting.create(9.3)

ifc = r"c:\temp\test.gdb\testMulti"

des = gp.Describe(ifc)
sfn = des.ShapeFieldName
oid = des.OIDFieldName

result = gp.GetCount_management(ifc)
cnt = int(result.GetOutput(0))
gp.AddMessage("%d features in feature class." % cnt)
cursor = gp.updatecursor(ifc)
row = cursor.next()
while row:
    feat = row.GetValue(sfn)
    pointArray = feat.GetPart()
    boolNeedsUpdate = 0
    pointCount = pointArray.Count
    pointIndex = pointCount - 1
    while pointIndex >= 0:
        point = pointArray.GetObject(pointIndex)
        if((point.z > 1000) or (point.z < 0)):
            boolNeedsUpdate = 1
            gp.AddWarning("Multipoint feature outside of threshold.")
            gp.AddMessage("%d -> %d -> %s" % (row.GetValue(oid), pointIndex, str(point.z)))
            pointArray.Remove(pointIndex)
        pointIndex -= 1
    if boolNeedsUpdate:
        gp.AddMessage("Removing point(s)")
        row.shape = pointArray
        cursor.UpdateRow(row)
    row = cursor.next()

What I'm doing is getting an array of point objects from the geometry object (GetPart() with no arguments returns an array of points instead of a single point object), then iterating through the array backwards since we're removing items from it, and removing the points with the invalid Z values. After that we set the row's shape to the new pointArray and update the row before moving on to the next row.

Re: Removing one point from a multipoint feature class

JohnReiser — Thu, 21 Oct 2010 01:24:56 GMT

This seems to work for me:

And it works for me, too. Many thanks!

Re: Removing one point from a multipoint feature class

DanLee — Sat, 06 Nov 2010 20:57:29 GMT

You might be able to use geoprocessing tools to do this:
1. Use Multipart To Singlepart tool to convert your multipoint feature class to single points. Each point will carry the ORIG_FID field.
2. Select the points you need to delete.
3. Run Delete Features tool.
4. Use Dissolve tool with ORIG_FID as the dissolve field. You should get your multipoints back.

Regards,