[Gdal-dev] Problem using gdal_translate on netcdf file

Hernán De Angelis dhdeangelis.listas at gmail.com
Tue Jan 23 04:26:41 EST 2007


Andrew,

I tried this morning with one of the netCDF grids that come with the
GMT examples (ex02/HI_topo2.nc). I did:

gdal_translate -scale -7438 2804 0 255 -ot Byte netCDF:"HI_topo2.nc":z test.jpg

and works good for me. This command exported to a 8bit image while
rescaling to the max and min of the netCDF grid to 0 and 255. One must
be careful in selecting the appropriate netCDF dataset.  You can
afterwards modify the colours in GIMP to make the image look nicer.

Cheers

Hernán


2007/1/22, Chase, Andrew <achase at mbari.org>:
> Thanks for the suggestion Hernán, I've already tried this (and tried it again just now to double check). When I set "-ot Byte" I still get a black image, this time in all formats including Gtiff, whereas before I got the vertical banding in Gtiff.
>
> Still searching...
>
> -Andrew
>
>
> ________________________________
>
>         From: gdal-dev-bounces at lists.maptools.org [mailto:gdal-dev-bounces at lists.maptools.org] On Behalf Of Hernán De Angelis
>         Sent: Saturday, January 20, 2007 1:21 AM
>         To: gdal-dev at lists.maptools.org
>         Subject: Re: [Gdal-dev] Problem using gdal_translate on netcdf file
>
>
>         Your files are in Float32 format, try rescaling them to 8bit:   gdal_translate -ot Byte
>
>
>         2007/1/20, Chase, Andrew <achase at mbari.org>:
>
>                 Hi All,
>
>                 I'm trying to convert a netcdf file to some an image format that I can use with imagemagick (tiff, jpg, png, anything will do). Unfortunately, I'm having some troubles getting the job done. When I try gdal_translate with any format other than Gtiff I get a completely black image. When I use the Gtiff format, I get a weird grayscale mutated version of my source file, with strange grainy vertical bands. When I open the netcdf file in OpenEV it looks perfectly normal, and I use the netcdf file for a lot of different data processing, so I feel confident that the data itself is good (if not the formatting of the data).
>
>                 I've placed a subsetted version of the translated image online to show what the resulting geotiff looks like, it's here:
>
>                 http://www.mbari.org/staff/achase/vdm/hrbath.tif <http://www.mbari.org/staff/achase/vdm/hrbath.tif>
>                 Maybe someone else has seen this same type of image problem?
>
>                 Here's the gdalinfo output:
>
>                 C:\workspace\vdm\resources\grids>gdalinfo NETCDF:"hrbath.nc":elevation
>                 Driver: netCDF/Network Common Data Format
>                 Size is 5001, 4001
>                 Coordinate System is `'
>                 Origin = (-125.000000000000000,38.000999999999998)
>                 Pixel Size = (0.000999800039992,-0.000999750062484)
>                 Metadata:
>                   NC_GLOBAL#creationDate=01/19/2007
>                   NC_GLOBAL#lastModified=01/19/2007
>                   NC_GLOBAL#Conventions=CF-1.0
>                   NC_GLOBAL#CreatedBy=VARS Data Mining Software - MBARI
>                   NC_GLOBAL#title=DEM Grid from hrbath.asc
>                   NC_GLOBAL#institution=MBARI
>                   NC_GLOBAL#creator_name=Andrew Chase
>                   NC_GLOBAL#keywords=dem bathymetry grid
>                   elevation#positive=up
>                   elevation#long_name=Elevation
>                   elevation#missing_value=-9.999900e+004
>                   elevation#units=meters
>                   latitude#units=degrees_north (+N/-S)
>                   longitude#units=degrees_east (+E/-W)
>                 Corner Coordinates:
>                 Upper Left  (-125.0000000,  38.0010000)
>                 Lower Left  (-125.0000000,  34.0010000)
>                 Upper Right (-120.0000000,  38.0010000)
>                 Lower Right (-120.0000000,  34.0010000)
>                 Center      (-122.5000000,  36.0010000)
>                 Band 1 Block=5001x1 Type=Float32, ColorInterp=Undefined
>                   NoData Value=-99999
>                   Metadata:
>                     NETCDF_VARNAME=elevation
>                 ----------------------------------------------------------------------------------------------------------
>
>                 And here's the translation I'm trying:
>
>                 C:\workspace\vdm\resources\grids>gdal_translate -of GTiff -a_nodata -99999 NETCD
>                 F:"hrbath.nc":elevation hrbath.tif
>                 Input file size is 5001, 4001
>                 0...10...20...30...40...50...60...70...80...90...100 - done.
>                 ----------------------------------------------------------------------------------------------------------
>
>                 And the resulting gdalinfo output:
>
>                 C:\workspace\vdm\resources\grids>gdalinfo hrbath.tif
>                 Driver: GTiff/GeoTIFF
>                 Size is 5001, 4001
>                 Coordinate System is `'
>                 Origin = (-125.000000000000000,38.000999999999998)
>                 Pixel Size = (0.000999800039992,-0.000999750062484)
>                 Metadata:
>                   NC_GLOBAL#creationDate=01/19/2007
>                   NC_GLOBAL#lastModified=01/19/2007
>                   NC_GLOBAL#Conventions=CF-1.0
>                   NC_GLOBAL#CreatedBy=VARS Data Mining Software - MBARI
>                   NC_GLOBAL#title=DEM Grid from hrbath.asc
>                   NC_GLOBAL#institution=MBARI
>                   NC_GLOBAL#creator_name=Andrew Chase
>                   NC_GLOBAL#keywords=dem bathymetry grid
>                   elevation#positive=up
>                   elevation#long_name=Elevation
>                   elevation#missing_value=-9.999900e+004
>                   elevation#units=meters
>                   latitude#units=degrees_north (+N/-S)
>                   longitude#units=degrees_east (+E/-W)
>                 Corner Coordinates:
>                 Upper Left  (-125.0000000,  38.0010000)
>                 Lower Left  (-125.0000000,  34.0010000)
>                 Upper Right (-120.0000000,  38.0010000)
>                 Lower Right (-120.0000000,  34.0010000)
>                 Center      (-122.5000000,  36.0010000)
>                 Band 1 Block=5001x1 Type=Float32, ColorInterp=Gray
>                   NoData Value=-99999
>                   Metadata:
>                     NETCDF_VARNAME=elevation
>
>
>
>                 Any ideas of what to try would be appreciated.
>
>                 -Andrew
>
>
>                 Andrew C. Chase
>                 Software Engineer
>                 Monterey Bay Aquarium Research Institute
>
>
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>
>
>
>
>
>
>         --
>
>         Hernán De Angelis
>         Linux user # 397217
>
>
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-- 

Hernán De Angelis
Linux user # 397217




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