Add DiscreteFrechetDistance #764

FObermaier · 2021-08-04T12:13:02Z

Like Hausdorff distance the Fréchet distance is a measure of similarity between curves.
Its metric is better than Hausdorff's because it takes the flow of the curves into account.
It is possible that two curves have a small Hausdorff but a large Fréchet distance.

This implementation is based on the following optimized Fréchet distance algorithm:

Thomas Devogele, Maxence Esnault, Laurent Etienne. Distance discrète de Fréchet optimisée. Spatial Analysis and Geomatics (SAGEO), Nov 2016, Nice, France. hal-02110055

It attempts to compute only relevant coordinate distances for perfromance.
It provides a minimal MatrixStorage base class and implementations that trade off memory consumption and performance.

Signed-off-by: Felix Obermaier felix.obermaier@netcologne.de

Signed-off-by: Felix Obermaier <felix.obermaier@netcologne.de>

* Fix HausdorffSimilarityMeasure to handle equal `POINT` geometries by using fast exit if `DiscreteHausdorffDistance.distance` returns 0d. * Add/extend unit tests

dr-jts · 2021-09-02T23:22:09Z

modules/core/src/main/java/org/locationtech/jts/algorithm/distance/DistanceFunction.java

+ *
+ * @author Felix Obermaier
+ */
+public interface DistanceFunction {


The term "function" is fairly overloaded in the JTS codebase. Can this be changed to DistanceMetric?

dr-jts · 2021-09-02T23:24:25Z

Frechet Distance is a nice addition to JTS.

How do you see the DistanceFunction capability being used? I see the example of a Scaled distance metric in the unit test - is this a real-world scenario? Does it change the Frechet Distance result by more than the scale factor?

dr-jts · 2021-09-02T23:27:40Z

It is very useful to have distance algorithms also be able to return the two points at which the calculated distance is obtained. This is for confirmation and visualization purposes. (For example see the implementation in DiscreteHausdorffDistance)

Is it possible to add this capability to the Frechet Distance code?

FObermaier · 2021-09-03T06:43:31Z

How do you see the DistanceFunction capability being used?

I thought about an implementation using Haversine or Vincenty's formula for geographic coordinates.

dr-jts · 2021-09-03T19:44:28Z

I thought about an implementation using Haversine or Vincenty's formula for geographic coordinates.

In geodetic space the locus of boundary segments between vertices is a great circle arc, rather than a straight line. So usually it requires more than just using a geodetic distance metric to produce accurate results. Of course, geometries can be densified to mitigate this somewhat.

i have had some thoughts about bundling up the various pieces of metadata about the geometry coordinate system (including geodetic information and precision model) into a single object (perhaps called GeometryRealm or maybe CoordinateSystem. Still thinking about whether this should be provided on a per-geometry basis (perhaps as part of the GeometryFactory), or on a per-operation basis. Or both... The advantage to doing this is that it will avoid a proliferation of objects and function signatures in the API.

Given this, I'd prefer to defer introducing the DistanceMetric API unless there is a clear current reason for doing so.

dr-jts · 2021-09-17T19:49:32Z

@FObermaier is there a bug in this algorithm? What should the Frechet Distance be between the following:

A: LINESTRING (1 1, 2 2)
B: LINESTRING (1 4, 2 3)

The implementation gives the distance as 2.23606797749979. But since the distance between the two start points is 3, shouldn't that be the overall Frechet Distance?

A fix has been developed in #783.

FObermaier · 2021-09-17T21:22:55Z

Yes, I'm working on it.

* Add getCoordinates() to DiscreteFrechetDistance * Add DiscreteFrechetDistanceLinear for validation of unit tests * Add unit test * Add code documentation to PointPairDistance

* Add DiscreteFrechetDistanceLinear to tests for verification. * Add MatrixStorage and implementations CsrMatrix, RectMatrix and HashMapMatrix * Add unit tests for MatrixStorage * Add unit tests

FObermaier · 2021-09-22T06:00:00Z

@dr-jts, I fixed the algorithm, sorry for doing PR too early.

* Add algorithm references * Add code documentation * Add references * Restrict test verbosity

dr-jts · 2021-09-29T16:56:34Z

modules/core/src/main/java/org/locationtech/jts/algorithm/distance/DiscreteFrechetDistance.java

+    int max = Math.max(rows, cols);
+    // NOTE: these constraints need to be verified
+    if (max < 64)
+      return new HashMapMatrix(rows, cols, Double.POSITIVE_INFINITY);


Is this faster? If not, why not just use a RectMatrix, since storage isn't a problem for small dimensions?

dr-jts · 2021-09-29T16:57:59Z

modules/core/src/test/java/org/locationtech/jts/algorithm/distance/MatrixStorageImplTests.java

+  /**
+   * Abstract base class for storing 2d matrix data
+   */
+  private abstract static class MatrixStorage {


It's unusual to duplicate implementation code in unit tests, since this doesn't actually test the code in the library?

I did not see another way to test and verify that MatrixStorage implementations work correctly while keeping it private in jts-core.

Yeah, that's a bit of a limitation in the Java package model. I usually make things like this package-private, so they can be unit tested.

* remove code duplication in unit test * remove constraint for HashMapMatrix

dr-jts · 2021-10-13T05:35:29Z

...ore/src/test/java/org/locationtech/jts/algorithm/distance/DiscreteFrechetDistanceLinear.java

+/**
+ * Linear Discrete Fréchet Distance computation
+ */
+public class DiscreteFrechetDistanceLinear {


What does this class do differently to DiscreteFrechetDistance? Are they both needed?

dr-jts · 2021-10-13T05:40:03Z

Computing the distance between the following geometries causes an ArrayIndexOutOfBoundsException.

A: LINESTRING (80 260, 170 180, 190 290, 310 350, 330 270, 360 280)
B: LINESTRING (120 90, 380 130)

It looks like the error occurs in the Bresenham diagonal generating method, when geometry B has fewer than half the vertices of geometry A.

dr-jts · 2021-10-13T17:35:52Z

modules/core/src/main/java/org/locationtech/jts/algorithm/distance/DiscreteFrechetDistance.java

+   *
+   * @param numCols the number of columns
+   * @param numRows the number of rows
+   * @return an array of column and row indices bitwise-or combined.


Is this correct? Or is the returned array a "flattened" set of X,Y indices?

FObermaier added 3 commits August 4, 2021 13:39

Add DiscreteFrechetDistance

c407274

Signed-off-by: Felix Obermaier <felix.obermaier@netcologne.de>

Add FrechetSimilarityMeasure

3692433

* Fix HausdorffSimilarityMeasure to handle equal `POINT` geometries by using fast exit if `DiscreteHausdorffDistance.distance` returns 0d. * Add/extend unit tests

Fix copy/paste leftover

ff6476c

dr-jts reviewed Sep 2, 2021

View reviewed changes

dr-jts added jts-core type-new-feature labels Sep 2, 2021

FObermaier added 4 commits September 21, 2021 22:38

Rename DistanceFunction to DistanceMetric

776a4a2

* Add getCoordinates() to DiscreteFrechetDistance * Add DiscreteFrechetDistanceLinear for validation of unit tests * Add unit test * Add code documentation to PointPairDistance

Remove DistanceMetric

6d68c96

Fix computeFrechet function

7ed25f5

* Add DiscreteFrechetDistanceLinear to tests for verification. * Add MatrixStorage and implementations CsrMatrix, RectMatrix and HashMapMatrix * Add unit tests for MatrixStorage * Add unit tests

Clean up

9aaa5ba

FObermaier force-pushed the enhancement/DiscreteFrechetDistance branch from 8db79ca to 9aaa5ba Compare September 21, 2021 21:39

Polish

a73f6a9

* Add algorithm references * Add code documentation * Add references * Restrict test verbosity

dr-jts reviewed Sep 29, 2021

View reviewed changes

Make MatrixStorage implementations package private

9a26ed5

* remove code duplication in unit test * remove constraint for HashMapMatrix

dr-jts merged commit e176732 into locationtech:master Oct 13, 2021

dr-jts reviewed Oct 13, 2021

View reviewed changes

dr-jts mentioned this pull request Oct 13, 2021

Fix DiscreteFrechetDistance Bresenham algorithm #783

Merged

dr-jts mentioned this pull request Dec 8, 2021

Stackoverflow in DiscreteFrechetDistance with ~larger linestrings (Windows) libgeos/geos#516

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jodygarnett added this to the 1.19.0 milestone Jun 21, 2022

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Add DiscreteFrechetDistance #764

Add DiscreteFrechetDistance #764

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Add DiscreteFrechetDistance #764

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