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Trace Network on ArcGIS 10 Solution

Question asked by ranleu on Oct 31, 2014

Hi, this is not a question but a way to trace a network on ArcGis 10 (trace tool is only available as of 10.1), provided it is topologically correct and the direction of the network is correct.

Basically

- Select the first segment of interest, in my case i did it with select by location.

- Extract vertex: if you are going upwards up the network then choose START vertex, if you are going downwards then choose END vertex.

- Create the following loop:

         Select next group of segments based on the extracted vertex; carefull it should be with the option BOUNDARY_TOUCH.

         Create feature/shape based on this selection

         Extract vertex again.

 

So, solved the looping control quite easily and fast, so here goes the whole deal (not such a big deal):

 

 

# Note: In my case I selected my first segment as being the one that intersects a given point. Of course you change this according to your needs.

arcpy.MakeFeatureLayer_management(your_point, 'your_point_lyr')

arcpy.MakeFeatureLayer_management(your_network, 'your_network_lyr')

arcpy.SelectLayerByLocation_management('your_network_lyr', 'INTERSECT', 'your_point_lyr')

arcpy.FeatureVerticesToPoints_management('your_network_lyr',start_vertex, "START")

print 'done start vertex'

 

 

# It is important to use BOUNDARY_TOUCHES, only then will it choose all segments touching that point. If you use INTERSECT it will only choose one segment.

# Save the new network outside the loop.

 

segment_river_before = 0

segment_river_after = 1

n = 0

while segment_river_after != segment_river_before:

    n +=1

    segment_river_before = int(arcpy.GetCount_management(your_network_lyr).getOutput(0))

    arcpy.MakeFeatureLayer_management(start_vertex, 'start_v_lyr')

    arcpy.SelectLayerByLocation_management('your_network_lyr', 'BOUNDARY_TOUCHES', 'start_v_lyr')

    segment_river_after = int(arcpy.GetCount_management(your_network_lyr).getOutput(0))

    arcpy.FeatureVerticesToPoints_management('your_network_lyr, start_vertex, "START")

    print 'No. of loops made, No. of river segments before and after', n, segment_river_before, segment_river_after

arcpy.CopyFeatures_management("net_lyr", new_net, "", "0", "0", "0")

print 'Yeiiiii, it worked'

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