[geotk] Netcdf Coverage

[Martin Desruisseaux]

Le 01/02/11 16:03, Fabien Carrion a écrit :
> In the metadata tab, selecting "Albedo", then the image description /
> dimensions / dimensions I don't have "Min value" or "Max value".
>
> Albedo is a percentage. I was waiting min value = 0 and max value = 100.
This may explain why the image is gray. Actually it is gray scale, but if 
"minValue" and "maxValue" are not provided the gray scale range in an arbitrary 
large scale (I don't remember which one exactly).

It may be worth to take a look again in the metadata tab, but by selecting 
"NetCDF - Albedo" instead than "Geospatial - Albedo" in the combo box. You 
should see the same metadata, but displayed as provided in the NetCDF file 
(without the ISO 19115-like rearangement performed by "Geospatial"). If you 
still don't see anything like min and max value, you may look rum "ncdump -h 
<yourfile>" one the command line to be really sure.

If min and max values are not provided, in current Geotk implementation you have 
the following choices:

    * If you have some control on the way the NetCDF file were generated, you
      may add the min and max attributes.
    * Otherwise you may try to create a subclass of NetcdfImageReader and
      override the "createImageMetadata" method in order to inject whatever
      "min" and "max" attribute you wish in the IIOMetadata object. Let me know
      if you choose this approach, so I can give some tips.
    * A more heavy approach (but may also be more powerful) could be to use the
      coverage-sql module, i.e. store the raster metadata (only the metadata,
      not the data values) in a PostgreSQL database. This provides better search
      capabilities in a large set of images, and give you more control on this
      kind of metadata. Let my know if you prefer this approach.

Regards,

     Martin