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I would like to make a buffer for a polyline and get as Output a Polygon with the same angles as the polyline, having not arcs, like in ordinary buffers.

i tried the FLAT option in arcpy, but it's applied to just the both ends.

enter image description here

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Can you post the code that you are using? – Taylor H. Feb 11 at 15:25
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Even if you can do this you migh have an issue with the polylines crossing each other which is why it may be difficult to create a tool that can do this automatically without any manual input. I will post a link to a tool I created for a similar purpose. – Jakub Feb 11 at 16:06

2 Answers

up vote 2 down vote accepted

i have made a function under arcpy to offset a polyline, for anyone may need this function under Arcpy:

the result: enter image description here

def offset(layer_in , layer_out , distance ):
    arcpy.Select_analysis(layer_in , "line_offset")
    arcpy.SplitLine_management("line_offset", "line_offset_split")
    arcpy.Buffer_analysis("line_offset_split", "line_offset_split_buf", distance  ,"FULL","FLAT","NONE")
    arcpy.FeatureVerticesToPoints_management("line_offset","line_offset_points", "ALL")
    arcpy.AddField_management("line_offset_points" , "X" , "DOUBLE" )
    arcpy.AddField_management("line_offset_points" , "Y" , "DOUBLE" )
    arcpy.CalculateField_management("line_offset_points", "X" , "!Shape.lastpoint.X!","PYTHON_9.3")
    arcpy.CalculateField_management("line_offset_points", "Y" , "!Shape.lastpoint.Y!","PYTHON_9.3")
    arcpy.Intersect_analysis(["line_offset_split_buf" ], "line_offset_split_buf_intersect" , "")
    arcpy.SpatialJoin_analysis("line_offset_split_buf_intersect"  , "line_offset_points" , "line_offset_split_buf_intersect_sj","JOIN_ONE_TO_ONE" , "KEEP_COMMON" , "" , "INTERSECT")##
    rows = arcpy.UpdateCursor("line_offset_split_buf_intersect_sj")
    for row in rows :
        x = row.getValue("X")
        y = row.getValue("Y")
        polyOuter = arcpy.Array()
        feat = row.Shape
        part = feat.getPart(0)
        for pt in iter(lambda:part.next(),None) : # iter stops on null pt
            polyOuter.append(arcpy.Point( 2*x - pt.X ,2*y - pt.Y) )
        row.setValue("Shape"  , arcpy.Polygon(polyOuter))
        rows.updateRow (row)

    arcpy.Append_management("line_offset_split_buf_intersect_sj","line_offset_split_buf","NO_TEST")
    arcpy.Dissolve_management("line_offset_split_buf", "line_offset_split_buf_disolv", "ID" , "", "SINGLE_PART")## the field is set to not dissolve all polygons
    arcpy.Generalize_edit("line_offset_split_buf_disolv", "0.001")
    arcpy.Select_analysis("line_offset_split_buf_disolv" , layer_out)
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up vote 5 down vote

You could try the Flat-end line buffer tool. I made it for a specific purpose for which it works fine. I sometimes merge the result to create a polygon from. The tool should work fine with 10.0. Have not tested in 10.1.

EDIT: There is a few parameters that can be set; distance, mitered or beveled, extend line ends. (for my purposes I needed to extend the line ends so i made that an option) Because it was made for specific purpose you should be aware that it does not resolve crossing lines (as I mentioned in my comment above). If anyone is interested I can illustrate what this looks like. Basically, resulting crossing lines have to be resolved manually before creating a polygon or polygon will result in a non-simple geometry.

I thought I would add some visuals to show what this basically does: enter image description here Result: enter image description here Result as polygon (also use a custom tool for that): enter image description here

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Thanks a lot , but i can use this add-on from a python script ? – geogeek Feb 11 at 16:33
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Can't say. I only use geoprocessing tools (that can be converted to Python) to call from VB.NET but not the other way around. I will share the code including the VS project if someone wants to try. – Jakub Feb 11 at 18:03
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The 'guts' of the script use the IConstructCurve:ConstructOffset method. – Jakub Feb 11 at 18:40
thanks a lot __ – geogeek Feb 11 at 20:47

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