Arcpy: creating a line on an existing line based on points' coordinates

Question

I have a point which is some meters away from an existing line:

enter image description here

This point should be snapped to the line (to the closest part) and then, based on the points' new coordinates, a new line Feature Class should be created, which is on the existing line 1,5 meters left and 1,5 meters right (so 3 meters total) of the point. Therefore it should look like the following picture:

enter image description here

Existing Datasets shouldn't be used, the result should be in a new FC.

Here is the code is used so far:

 import arcpy
 arcpy.env.workspace = arcpy.GetParameterAsText(0)
 point_feature = arcpy.GetParameterAsText(1)
 line_feature = arcpy.GetParameterAsText(2)
 # Make backup copy of point feature class, since modification with
 # the Editing tools below is permanent
 arcpy.CopyFeatures_management(point_feature, "point_feature_backup")
 # Snapping-Tool
 arcpy.Snap_edit(point_feature,[[line_feature,"EDGE","50 METERS"]]) 
 # Getting the coordinates of the new snapped Point
 with arcpy.da.SearchCursor(point_feature, ['SHAPE@XY']) as cursor:
 print ("Coordinates of the snapped point: {}".format(row[0]))
 # Creating the new line, I used phantasy coordinates here, it was just a test, the new Coordinates should be on the already existing line 1,5m left and 1,5m right of the snapped point
 cursor = arcpy.da.InsertCursor(line_feature, ["SHAPE@"])
 array = arcpy.Array([arcpy.Point(1823123.213, 6139654.819),
 arcpy.Point(1823123.244, 6139654.869)])
 polyline = arcpy.Polyline(array)
 cursor.insertRow([polyline])

The hardest part for me is to find out how to get the 1,5m on both sides...which tools could be used to do that or is there an alternative way?

Answer 1

There are two answers depending on your definition of distance: bird's flight or along the road. they wil be identical on a straight line but differ on curves or broken lines.

bird's flight

you could create a buffer around your point, then intersect the buffer geometry with the line. You can do this for all your points at once using the geoprocessing tool on the feature class or work on the geometry objects within a cursor.

with arcpy.da.SearchCursor(point_feature, ['SHAPE@']) as cursor:
 for row in cursor:
 buffer = arcpy.Buffer_analysis(row[0], arcpy.Geometry(), "1.5 meters")[0]
 line_feature = arcpy.Clip_analysis(input_lines, buffer, arcpy.Geometry())[0]
#do what you want with the resulting geometry 

Distance along line

For distance along line you can use linear referencing tools. You'l first need to create measures on your lines, then you can locate the feature along the route and then create a route event by adding/removing 1.5m from your point measured value. The created layer can be stored as a geometry if needed. (with arcpy copy )

• Duddel: thank you. Isn't there an option to achieve that using geometry objects?
• radouxju: you can use buffer and intersect on the geometry objects
• radouxju: see eg gis.stackexchange.com/questions/109451/…
• radouxju: or blogs.esri.com/esri/arcgis/2010/02/23/…
• FelixIP: It can be achieved by using combination of measureOnLine positionAlongLine (10.2 or higher) on geometry services. Remember buffer and linear referencing will produce the same (very close) results for straight line only