Using SimplifyByStraightLinesAndCircularArcs to help convert taxlot polygons from ArcMap to Fabric (ArcPro Fabric 3.1x)

Question

I am working with a new taxlot dataset that requires building the fabric from just polygons (which is new to me).  I am following the documented recommendation to use "SimplifyByStraightLinesAndCircularArcs" (without it I end up creating WAY to many lines).  In some cases the conversion converts lines to curves that I do not think should be converted and it is a problem.  I have changed the parameters for max_offset,  max_arc_angle_step, min_arc_angle, and min_vertex_count to MANY alternatives. Some of the silly (see below) and some push the options to extremes.  But the changes do not seem to impact the outcome. For example, you would think a max offset of .01 would mean lines would not deviate from the original by more the .01 (or so).  But that is not the case and it appears I get offsets close to .1.

arcpy.edit.SimplifyByStraightLinesAndCircularArcs(
        in_features=OutClassTxLtPly,
        max_offset="0.01 Feet",
        fitting_type="FIT_TO_VERTICES",
        circular_arcs="CREATE",
        max_arc_angle_step=2,
        min_vertex_count=4,
        min_radius=None,
        max_radius=None,
        min_arc_angle=2,
        closed_ends="PRESERVE",
        anchor_points=None
    )

The taxlot dataset I am converting is pretty typical and contains rural and urban maps.

My question is...

Is there a best practice or are there recommended options (besides using the defaults) for running this tool on parcels to create an optimal result ???

TimHodson · Answer

hi Dean,

The effect you were seeing where circular arcs fall outside the tolerance can be solved in two different ways, as specified by the bullet points. It’s either/or, not both. Sorry it was not very clear in the original post, I've edited the post to clarify.

-Tim

DeanAnderson2 · Answer

Tim (as usual sorry to be so late in responding)

The Max_arc_Angle step is not available if the Fit To Segments option is selected. From the documentation....

"This parameter is not available if the Fit to segments option is specified for the Fitting Type parameter."

TimHodson · Answer

@DeanAnderson2   I can give possible reasons for two of the items you mention, the one about circular arcs getting created when you don't what them to be, and the other about resulting feature geometry being outside the specified offset. Without seeing examples it's hard to know if these make sense for your cases.

It is possible that the Simplify By Straight Lines and Circular Arcs GP tool can result in a circular arc that bows out beyond the Maximum Allowable offset from the initial feature’s geometry. This may occur if you chose the Fit to Vertices option, and it is also more likely to occur with a larger value for the Arc Angle Step.

The algorithm works by taking the positions of the vertices and trying to fit straight lines and circular arcs and by allowing the positions of any of the original feature vertices (except the first and last vertex of the feature) to be iteratively varied within the Maximum Allowable offset until a best-fit circular arc and/or straight line can be found.

This can result in a new circular arc that bows outside of the offset distance while not breaking the conditions of the algorithm because the original vertices that are used to define the circular arc are still within the allowable offset. Here's a graphic showing this:

To avoid the likelihood of this happening, you can either:

* Use the Fit to segments option instead, because this option uses the segment geometry, OR
* Reduce the value for the Arc Angle Step if you are using the Fit to vertices option.