Resampling technique when Exporting Raster to Geotiff

Yahya1981Yahya1981 Global Mapper UserPosts: 2
edited March 2012 in Raster Data
Dear GM support,

Hi, I used GM for exporting the raster image from tiff (32bit, cellsize 0.25 degree) to Geotiff (16bit, cellsize 0.00083 degree). I surprised because I got smoother image than using Arc Map 9.3. I am just wondering what kind of resampling technique that used in GM? Because I need to explain for my report about the principle beside this tools. I already compared GM's result to the ArcMap's results and GM's result is better than ArcMap.

Many thanks in advance.

Regards,
Yahya

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited March 2012
    Yahya,

    Was this an elevation GeoTIFF or just an image? By default bilinear interpolation will be used for terrain display and exports. If you are resampling or reprojecting the same will be used for raster exports at about the same resolution as the original. If sub-sampling significantly then box averagers will automatically be used by default, but it looks like you are oversampling and not subsampling.

    Thanks,

    Mike
    Global Mapper Guru
    gmsupport@bluemarblegeo.com
    http://www.globalmapper.com
  • Yahya1981Yahya1981 Global Mapper User Posts: 2
    edited March 2012
    Dear Mike,

    My image is elevation Geotiff from TRMM satellite. Could you explain a little bit what the difference between oversampling and sub-sampling? So for my case, the resampling technique is bilinear interpolation? Thank you.


    Regards,
    Yahya
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited March 2012
    Yahya,

    Oversampling is when you resample your data a a higher resolution than the original data. For example exporting 10m resolution data at 5m resolution. Sub-sampling is resampling to a lower resolution, for example exporting 10m resolution data at 30m resolution.

    Thanks,

    Mike
    Global Mapper Guru
    gmsupport@bluemarblegeo.com
    http://www.globalmapper.com
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