[GIS] Intersection with JTS Geometry

geometryintersectionjts-topology-suite

I want to calculate an intersection between two geometries with the intersection function from JTS Geometry.
What happens, if the geometries have different SRIDs?

SimpleFeature sf1=...;      //SRID 31467
SimpleFeature sf2=...;      //SRID 4327

Geometry geom1 = (Geometry) sf1.getDefaultGeometry();
Geometry geom2 = (Geometry) sf2.getDefaultGeometry();

Geometry overlay = geom1.intersection(geom2);

Does the function calculate the intersection in respect to the different SRIDs or does it ignore it?
Which SRID does the calculated geometry have?

I didn't find any documentation about that.

Best Answer

As far as I know JTS does nothing with the SRID value (see this email). You will need to use GeoTools to reproject your features to a common projection and then call intersection on them. The result will then be in the common projection and you can then project back to one or both of the input projections.

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[GIS] Querying intersecting areas areas – Oracle Locator or Spatial

The Oracle Spatial 10gR1 user guide lists supported Locator functionality here. This page links to another page that describes functions supported by Locator.

This list includes SDO_RELATE, which is another approach to checking for geometry intersections.

e.g. (from the SDO_RELATE section)

  SELECT c.mkt_id, c.name
  FROM cola_markets c
  WHERE SDO_RELATE(c.shape,
    SDO_GEOMETRY(2003, NULL, NULL,
      SDO_ELEM_INFO_ARRAY(1,1003,3),
      SDO_ORDINATE_ARRAY(4,6, 8,8)),
    'mask=anyinteract') = 'TRUE';

The intersection query will be handled by Oracle, not GeoServer. I once had to trace a GeoServer WMS query in Oracle and I'm pretty sure it used the SDO_RELATE approach, but you might want to verify this using your own trace, scanning through the GeoServer source, or posting a question on the GeoServer users mailing list

[GIS] the difference between Spatial predicates “Covers” and “Contains”

Look at Martin Davis (creator of the JTS Topology Suite), Lin.ear th.inking: Quirks of the "Contains" Spatial Predicate

Geometry A contains Geometry B if no points of B lie in the exterior of A, and at least one point of the interior of B lies in the interior of A
Geometry A covers Geometry B if no points of B lie in the exterior of A

All that is necessary to determine this condition is to perform a simple bounding box comparison. This is not possible with contains, because even if the bounding box of Geometry is covered by the Rectangle, a further expensive operation is required to test if the Geometry lies wholly in the boundary of the Rectangle (in which case the predicate fails). Covers "simplifies" the definition of contains by making it more general (inclusive)

If you look at DE-9IM, you can see that contains (T*****FF*) is a particular case of covers (T*****FF*, *T****FF*, ***T**FF*)

For example, the definition of contains implies that a Polygon do not contain its boundary but a Polygon covers its boundary.

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Best Answer

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[GIS] Querying intersecting areas areas – Oracle Locator or Spatial

[GIS] the difference between Spatial predicates “Covers” and “Contains”

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