Global Mapper Pro

Max_elev ver 11.02 vs 12

rayngwt
rayngwt Global Mapper UserTrusted User
edited November 2010 in Elevation Data
Hi Mike
Just got a question abt the difference in the below results.

In ver 11.02, using below vertices and srtm30 I got a max_elev of 13192.23 ft.
This is the Mt Kinabalu area in Borneo using the E100N40 tile.

In ver 12, same conditions, I got a max_elev of 12716.51 ft. (latest .exe)

Idx,Longitude,Latitude
1,116.0000000000,7.0000000000
2,117.0000000000,7.0000000000
3,117.0000000000,6.0000000000
4,116.0000000000,6.0000000000
5,116.0000000000,7.0000000000

I have downloaded your latest .exe as per the previous max_elev topic where we talked about the contours and max_elev not matching. Please kindly advise if the results should be what they are.

Many thanks,
Ray

Comments

  • global_mapper
    global_mapper Administrator
    edited November 2010
    Ray,

    The issue is where the sampling of the layers is being done and the resampling method (defaulting to bilinear interpolation for elevation layers) used. I decided to update the min/max elevation calculation portion of the area elevation statistics calculation to not do interpolation so the true minimum and maximum can always be found. I have placed a new build at http://www.globalmapper.com/global_mapper12.zip with the change for you to try. Simply download that file and extract the contents into your existing v12.xx installation folder to give it a try. If you are using the 64-bit v12 version there is a new build at http://www.globalmapper.com/global_mapper12_64bit.zip .

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • rayngwt
    rayngwt Global Mapper User Trusted User
    edited November 2010
    Hi Mike,

    Thanks.

    1. So I just want to clarify that the default GM method in all versions prior to 11 and also ver 12, is to interpolate the max_elev and not true?
    2. So ... in this thread here the exe and dll are interpolated? where as the thread we were talking about the Quito area (the exe/dll) was 'adjusted' to true?
    3. Also, the contour function has always been true?

    I'm sorry I'm kind of confused here and which will be the default method with v12.

    Thanks, Ray
  • global_mapper
    global_mapper Administrator
    edited November 2010
    Ray,

    The method used depended on the resampling method specified for the elevation layers used, which would default to bilinear interpolation. In the new build for determining the min/max elevation values in the entire area feature now interpolation will never be used as it is not desirable for those functions. For all other statistics the selected resampling method will still be used. The same applies for contour generation as well.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • rayngwt
    rayngwt Global Mapper User Trusted User
    edited November 2010
    Ok, Thanks Mike,

    So, is it possible to have this option of non-interpolation in a future build ? This latest build in this thread does interpolation for area min/max. I'm new to this and thanks for your patience.

    Ray
  • global_mapper
    global_mapper Administrator
    edited November 2010
    Ray,

    The option already exists to do non-interpolation, you just need to select the elevation layers in the Control Center, press Options, then change the resampling method to 'Nearest Neighbor' to disable interpolation.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • rayngwt
    rayngwt Global Mapper User Trusted User
    edited November 2010
    Hi Mike,

    Thanks ... so I gather that the default for both area max and contour depends on the terrain resampling method chose, and that the current build at Nov5 (globalmapper download) is the 'true' compiler to be used.

    Ray
  • global_mapper
    global_mapper Administrator
    edited November 2010
    Ray,

    For everything except for the determination of the MIN_ELEV and MAX_ELEV attributes for area statistic calculation (which in the latest Nov 21st or later build will never use interpolation for those attributes), the resampling method chosen for a layer determines the behavior.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • rayngwt
    rayngwt Global Mapper User Trusted User
    edited November 2010
    Ok, tks Mike.

    Thanks for yr patience, was confusing at first.

    Ray
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