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Add Polygonal Coverage simplification #911

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merged 23 commits into from
Oct 6, 2022

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@dr-jts dr-jts commented Oct 6, 2022

Adds the CoverageSimplifier class to the coverage package. This supports simplification of the edges of polygonal coverages while preserving the coverage topology:

  • The simplified coverage has the same number and types of polygonal geometries as the input
  • Coverage node points (inner vertices shared by three or more polygons, or boundary vertices shared by two or more) are not changed
  • if the input is a valid coverage, then so is the result

The simplification uses an approach equivalent to Visvalingam-Whyatt simplification. This is based on removing vertices which are the apex of low-area "corners". The amount of simplification is determined by a tolerance value which is the square root of the maximum corner area that can be removed.

Simplification of France regions, tolerance = 0.2
image

The simplifier supports an option to simplify only the inner (non-boundary) edges of the coverage. This allows simplifying portions of a large coverage, and ensuring the simplified result fits seamlessly with the original.

Inner Simplification of France regions, tolerance = 0.2
image

Signed-off-by: Martin Davis <mtnclimb@gmail.com>
Signed-off-by: Martin Davis <mtnclimb@gmail.com>
Signed-off-by: Martin Davis <mtnclimb@gmail.com>
Signed-off-by: Martin Davis <mtnclimb@gmail.com>
Signed-off-by: Martin Davis <mtnclimb@gmail.com>
Signed-off-by: Martin Davis <mtnclimb@gmail.com>
Signed-off-by: Martin Davis <mtnclimb@gmail.com>
Signed-off-by: Martin Davis <mtnclimb@gmail.com>
Signed-off-by: Martin Davis <mtnclimb@gmail.com>
Signed-off-by: Martin Davis <mtnclimb@gmail.com>
Signed-off-by: Martin Davis <mtnclimb@gmail.com>
Signed-off-by: Martin Davis <mtnclimb@gmail.com>
Signed-off-by: Martin Davis <mtnclimb@gmail.com>
Signed-off-by: Martin Davis <mtnclimb@gmail.com>
Signed-off-by: Martin Davis <mtnclimb@gmail.com>
Signed-off-by: Martin Davis <mtnclimb@gmail.com>
Signed-off-by: Martin Davis <mtnclimb@gmail.com>
Signed-off-by: Martin Davis <mtnclimb@gmail.com>
Signed-off-by: Martin Davis <mtnclimb@gmail.com>
Signed-off-by: Martin Davis <mtnclimb@gmail.com>
Signed-off-by: Martin Davis <mtnclimb@gmail.com>
Signed-off-by: Martin Davis <mtnclimb@gmail.com>
Signed-off-by: Martin Davis <mtnclimb@gmail.com>
@dr-jts dr-jts merged commit 30b674a into locationtech:master Oct 6, 2022
@dr-jts dr-jts deleted the add-cov-simplify branch October 6, 2022 22:56
pramsey added a commit to libgeos/geos that referenced this pull request Apr 11, 2023
Adds the CoverageSimplifier class to the coverage package. This supports simplification of the edges of polygonal coverages while preserving the coverage topology:

    The simplified coverage has the same number and types of polygonal geometries as the input
    Coverage node points (inner vertices shared by three or more polygons, or boundary vertices shared by two or more) are not changed
    if the input is a valid coverage, then so is the result

The simplification uses an approach equivalent to Visvalingam-Whyatt simplification. This is based on removing vertices which are the apex of low-area "corners". The amount of simplification is determined by a tolerance value which is the square root of the maximum corner area that can be removed.
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