[postgis-users] WKB4J

[Paul Ramsey]

The reference we used originally was this proposal.

http://gdal.velocet.ca/projects/opengis/twohalfdsf.html

Dave Blasby wrote:
> 
> David Garnier wrote:
> > > Are you handling 3d points?  PostGIS (and several other WKB-producing
> > > Open Source projects) are adding 80x (128 decimal) to the WKB type and
> > > then putting in 3 doubles for points (x,y,z).
> >
> > Well right now it doesn't, but it would just require one switch case and 3 more methods in the Factory interface. Do you have a reference where I could learn more about this?
> 
> There isnt a reference for it, unfortunately.
> 
> PostGIS will produce 3D WKB by default if there are 3d points in the
> geometric object.
> 
> For example,
> 
> > SELECT asBinary('POINT(0 1 2)');
> > SELECT asBinary('LINESTRING(0 0 0, 1 1 1)');
> 
> Note; you can convert a 3d geometry into a 2d geometry by calling the
> force_2d() function on it:
> 
> > SELECT force_2d('POINT(0 1 2)');
>         -> POINT(0 1)
> > SELECT force_2d('LINESTRING(0 0 0, 1 1 1)');
>         -> LINESTRING(0 0, 1 1)
> 
> enum wkbGeometryType {
> wkbPoint = 1,
> wkbLineString = 2,
> wkbPolygon = 3,
> wkbMultiPoint = 4,
> wkbMultiLineString = 5,
> wkbMultiPolygon = 6,
> wkbGeometryCollection = 7,
> 
> wkbPoint3d = 129,
> wkbLineString3d = 130,
> wkbPolygon3d = 131,
> wkbMultiPoint3d = 132,
> wkbMultiLineString3d = 133,
> wkbMultiPolygon3d = 134,
> wkbGeometryCollection3d = 135
> };
> 
> Point {
> double x;
> double y;
> };
> 
> Point3d {
> double x;
> double y;
> double z;
> };
> 
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     | Paul Ramsey
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