[gdal-dev] ISO WKB

[Pepijn Van Eeckhoudt]

On 13-12-13 00:24, Paul Ramsey wrote:
> The GeoPackage document actually specifies a representation for POINT 
> EMPTY,  "In GeoPackages these points SHALL be encoded as a Point where 
> each coordinate value is set to an IEEE-754 quiet NaN value".
I'm to blame for this one. It's specified in the GeoPackage spec because 
it's not specified in SFSQL or SQLMM and I didn't want to leave this as 
an unspecified part of the encoding.

The reason I pushed for the nan based encoding is that it provides an 
encoding of 'point empty' that does not lose information. The 
alternative of encoding it as null or multipoint empty changes the 
semantics of the object. If you stick with the point wkb type then the 
only option for special values is special double values. point(nan nan) 
seemed like a reasonable approximation of point empty; a point where the 
coordinates are not valid numbers.

If you think this is a bad idea or causes real difficulties in 
implementation please let me know, I'll bring it up in the geopackage 
swg then. Alternative solutions are also welcome of course.

Pepijn
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