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XYZ resampling options

DARDAR Global Mapper UserPosts: 2
edited January 2015 in Elevation Data
Hi,

When exporting an .xyz several options for resampling are provided. Is there any document in which I can find the description of these? I would like to understand in which consists the "Default (Resample if Needed)" option and why it differs from the box average.

Thanks for the help!

Comments

  • PShoreyPShorey Global Mapper Developer Posts: 195Moderator, Trusted User
    edited January 2015
    DAR,

    Essentially, the default option will result in Global Mapper automatically picking the best resampling method given the data to be exported. This will generally be bilinear, though one of the box max or average methods may be used depending on the spatial resolution. Automatic mode can be disabled in the configuration settings, resulting in the resampling method configured in each layer to be used (see in control center | options ). To see a description of the types of resampling, open the help file and go to Overlay Control Center | Options | Elevation Data Options | Display Tab.

    Hope this helps,
    Peter
  • DARDAR Global Mapper User Posts: 2
    edited January 2015
    Thank you, Peter.

    After going through the description, I still have a few questions regarding the samples chosen for the calculations. For example, if working with an elevation grid with a 5m resolution:

    - When choosing the bilinear interpolation for a resolution of 25m (5x5). Is the bilinear interpolation going to take into account the whole 25x25 m square or just the small 10mx10m square (2x2, neighbor points)?

    - Also, if you want to extract a box average for a 50 m resolution (10x10), if you use a box average (9x9) and just change the resolution is it going to include all the samples or just pick random 9x9 ?

    Thanks for your help!
  • PShoreyPShorey Global Mapper Developer Posts: 195Moderator, Trusted User
    edited January 2015
    Dar,

    The bilinear interpolation will use the neighboring points only. Likewise, the 9x9 box will use: 4 to the left/down to 5 to the right/up.
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