Saga binary grid driver seems to ignore specified nodata values

[Alister]

I am on Windows (OWGeo4W).

When I create a Saga binary grid using the gdal command line tools (e.g. gdalwarp and gdal_translate), the -a_nodata option is ignored. It seems like there are default nodata values which are always used for a given band data type.

e.g. when creating an Int16 grid, the nodata value is always set to -32767, which is particularly strange when I am creating it by translating from a file with a nodata value of -32768, as the values in the image stay at -32768, but the nodata value is set to -32767 ;) When creating a UInt16 grid, the nodata value is always set to 65535.

Is there something I'm missing here? Does Saga binary grid (or its gdal driver) not support nodata values? If so, shouldn't there be a warning message or something?

Thanks.

[warmerdam]

cc:ing Volker. If the driver does not natively support nodata then it likely ought to let it be handled via PAM mechanisms.

[vwichmann]

Yes, at the moment the GDAL dataformat (GDT) is used to map to SAGA's NoData values. This is hardcoded in sagadataset.cpp (NoData definition is line 44ff, Mapping is done in line 82ff).

I need to have a more detailed look on how the NoData handling has to be changed within the driver. Suggestions welcome (e.g. which mechanism is preferred, how is NoData handling is supported by other drivers etc).

Volker

[Even Rouault]

Fixed in trunk (r22676) and in branches/1.8 (r22677)

[Even Rouault]

Milestone 1.8.2 deleted