I am trying to edit the geometry of one polygon to match another polygon, same as in this question:

Snapping polygons while reshaping edges?

Unfortunately, using the Reshape and Trace editing tools is achingly slow and tedious and I have a bunch of locations spread across a bunch of polygons that require this editing. I also tried the Enable Tracing tool in QGIS as this thread suggests: Adjust polygons by edition (freehand and reshape tools used together) to no avail.

Are there any other approaches that have worked for others to do this efficiently?

Just doing a rough reshape and then clipping or erasing (as suggested in the first thread) gets complicated since the lines intersect in both directions (see image). I want to align the low-res black polygon to the high-res blue polygon in specific places.

enter image description here

  • You could try to run simplify geometries on the high-res polygon. – Erik Jan 26 at 15:14
  • Removed tag for ArcGIS Desktop to focus question on QGIS. Feel free to ask a separate question about ArcGIS Pro or ArcMap. – PolyGeo Jan 26 at 20:14
  • Is the black polygon a crude match in extent to the blue polygon or is it a crude fill of the hole in the blue polygon? – johns Jan 26 at 20:37
  • They are distinct layers... the black line polygon representing a unique aquatic ecological area and the blue polygon representing a high-res coastline. Both polygons showing marine areas (the white being land). – mikeLdub Jan 26 at 21:13
  • This looks like a datum transformation shift. – Vince Jan 26 at 23:47

Turn the question around. Instead of trying to reshape the simple polygon to match the detailed polygon, create a copy of the detailed polygon and inherit the attributes of the simple polygon using a spatial join.

QGIS methodology:

In the Processing Toolbox use the Vectory general > Join attributes by location tool using the following parameters:

  • Base layer - complex polygon
  • Join Layer - simple polygon
  • Fields to add - Whichever attributes you want the new dataset to inherit from the simple polygons
  • Discard records which could not be joined - checked

Everything else you can leave as default.

Open the attribute table of the new dataset and delete the fields from the original complex polygon.

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