Global Mapper v26.0

export DEM floating point issue - might be user problem

Mikedunn
Mikedunn Global Mapper User
edited February 2009 in Bug Report
Still using 9.03.

GM is a fantastic tool!

Biggest issue I have run into is that DEMs export with integer values and even very dense LiDAR surfaces look artificial (layers of LEGOs).

How can I export DEMs with floating point values?

Thanks!

Comments

  • global_mapper
    global_mapper Administrator
    edited February 2009
    Which format are you exporting to? Many formats support floating point elevation values, and for those that don't (like Global Mapper Grid or DEM), just use more precise elevation units like decimeters instead of meters.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • Mikedunn
    Mikedunn Global Mapper User
    edited February 2009
    I'm exporting to DEM. Arcinfo allows floating point DEMs although the default is integer.

    DEM is a very efficient import format for my destination software, earthVision, so I use DEM when I can.

    Changing units didn't help. I abandoned DEM and went with "Export XYZ Grid" but there were too many data points (>4 million) for the earthVision gridder (although the ability to output RGB data yielded spectacular results in the earthVision Viewer!)

    I finally used ArcMap to create and populate a TIN, created a floating-point grid at optimal spacing, then created a floating point DEM from the arc: prompt.

    For smaller datasets, XYZ Grid works great but have to use ArcINFO DEM for the big ones.

    Thanks again.I'm exporting to DEM. Arcinfo allows floating point DEMs although the default is integer.

    DEM is a very efficient import format for my destination software, earthVision, so I use DEM when I can.

    Changing units didn't help. I abandoned DEM and went with "Export XYZ Grid" but there were too many data points (>4 million) for the earthVision gridder (although the ability to output RGB data yielded spectacular results in the earthVision Viewer!)

    I finally used ArcMap to create and populate a TIN, created a floating-point grid at optimal spacing, then created a floating point DEM from the arc: prompt.

    For smaller datasets, XYZ Grid works great but have to use ArcINFO DEM for the big ones.

    Thanks again.I'm exporting to DEM. Arcinfo allows floating point DEMs although the default is integer.

    DEM is a very efficient import format for my destination software, earthVision, so I use DEM when I can.

    Changing units didn't help. I abandoned DEM and went with "Export XYZ Grid" but there were too many data points (>4 million) for the earthVision gridder (although the ability to output RGB data yielded spectacular results in the earthVision Viewer!)

    I finally used ArcMap to create and populate a TIN, created a floating-point grid at optimal spacing, then created a floating point DEM from the arc: prompt.

    For smaller datasets, XYZ Grid works great but have to use ArcINFO DEM for the big ones.

    Thanks again.
  • global_mapper
    global_mapper Administrator
    edited February 2009
    The USGS DEM format specification does not allow floating point values, so ArcINFO must be using a different format if they are storing floating point values in it. If you used decimeters for your elevation units you should get a precision of 0.1 meter for each elevation value in the file (perhaps this is what ArcINFO is doing and referring to as floating point DEM, even though internally in the DEM file the values are still integers, just integer decimeter values).

    There are lots of other formats that support full floating point precision, like Float/Grid, 32-bit elevation GeoTIFF, etc.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com

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