Getting polyline length wise in dataframe in layout view in ArcMap via rotation?

Question

I'd like to rotate my dataframe until a polyline fits dataframe-width wise in the layout view of a .mxd. If the lines runs north/south I would like the dataframe rotated until the line is shown east/west (the north arrow adjusts accordingly).

I can rotate the dataframe with arcpy. But how would I check that my polyline is running dataframe-width wise.

Or would I get the envelope of the feature and then do some math to figure out how much the rotation angle should be to have the data frame rotated to meet my goal?

The end result would be to capture the entire polyline in the dataframe in layout view of ArcMap (dataframe-width wise) at the smallest extent possible. Like an alignment sheet.

Answer 1

Assuming that there are no curves in your line, this function accepts a featureclass containing your single polyline (you can use an in_memory feature class constructed on the fly) to rotate the data frame to show the line east/west.

Note that I am using 10.1 right now, so there is one function in this, RemoveTableview that might not work in 10.0. I could not find it in the 10.0 documentation. If so, you can take that out, but you might have to do some cleanup to remove the reference to the in memory table from your mxd. This is not the fastest function out there, but the particular problem you have, finding the longest dimension across a polyline, is an O(n!) operation AFAIK, and so the PointDistance tool is going to be your best bet. FeatureVerticesToPoints is a pretty costly operation too, as well as freeing up the in_memory feature class at the end (but at least that is better than writing to disk).

def rotateToPolyline(fc):
    mxd = arcpy.mapping.MapDocument("CURRENT")
    df = arcpy.mapping.ListDataFrames(mxd)[0]
    vname = arcpy.CreateUniqueName("Vertices", "in_memory")
    dname = arcpy.CreateUniqueName("Distances", "in_memory")
    arcpy.FeatureVerticesToPoints_management(fc, vname)
    vertices = arcpy.Describe(vname)
    arcpy.PointDistance_analysis(vertices.name, vertices.name, dname)
    distances = arcpy.Describe(dname)
    rows = arcpy.SearchCursor(distances.name)
    max = 0
    from_id = -1
    to_id = -1
    for row in rows:
        if row.getValue("DISTANCE") > max:
            max = row.getValue("DISTANCE")
            from_id = row.getValue("INPUT_FID")
            to_id = row.getValue("NEAR_FID")
    if max > 0:
        oidfield = arcpy.AddFieldDelimiters(vertices.name, vertices.OIDFieldName)
        pt_from = arcpy.SearchCursor(vertices.name, oidfield + " = " + str(from_id))
        pt_to = arcpy.SearchCursor(vertices.name, oidfield + " = " + str(to_id))
        pt_from = pt_from.next().getValue(vertices.ShapeFieldName)
        pt_to = pt_to.next().getValue(vertices.ShapeFieldName)
        rise = pt_to.firstPoint.Y - pt_from.firstPoint.Y
        run = pt_to.firstPoint.X - pt_from.firstPoint.X
        df.rotation = -math.degrees(math.atan2(rise, run))
    else:
        df.rotation = 0
    df.zoomToSelectedFeatures()
    arcpy.mapping.RemoveLayer(df, arcpy.mapping.Layer(vertices.name))
    arcpy.Delete_management(vname)
    #RemoveTableView might not work in 10.0
    arcpy.mapping.RemoveTableView(df, arcpy.mapping.TableView(distances.name))
    arcpy.Delete_management(dname)