[gdal-dev] vector NODATA for Z values?

[Rahkonen Jukka]

Hi,

I think that it depends on the file format. Rather often it is set to zero but I have seen NaN in many places. However, shapefiles explicitly denies NaN

"...Positive infinity, negative infinity, and Not-a-Number (NaN) values are not allowed in shapefiles. Nevertheless, shapefiles support the concept of "no data" values, but they are currently used only for measures. Any floating point number smaller than -1038 is considered by a shapefile reader to represent a "no data" value.

With the SQLite dialect it is possible to select the value but NaN is not accepted.
Can be tested with
ogrinfo -dialect SQLite -sql "select CastToXYZ(ST_GeomFromText('POINT (1 2)'),3)" point.json

-Jukka Rahkonen-

Lähettäjä: gdal-dev <gdal-dev-bounces at lists.osgeo.org> Puolesta Abel Pau via gdal-dev
Lähetetty: torstai 25. tammikuuta 2024 19.07
Vastaanottaja: gdal-dev at lists.osgeo.org
Aihe: [gdal-dev] vector NODATA for Z values?

Hi,
there is any value in GDAL for VECTORS that indicates that a concrete value of a Z is not known (z nodata value)?
I couldn't find it anywhere.

In MiraMon format we use one concrete number documented in our format pdf (-1.0E+300) an in the driver it's planned to translate it to the same number. I could translate it to the one I am asking. And the same for detecting nodata Z and translate them to -1.0E+300 when reading another format.

Thanks!


Abel Pau Garcia
GIS developer
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