Null Data Value

miksmith
miksmith Global Mapper UserTrusted User
edited January 2008 in Suggestion Box
Are null data values supported anywhere in GM?? The Arc GRID files I have been importing to ERDAS Imagine, by default, use -9999, however the batch importer doesn't appear to have an option for setting null data value (something that is now supported in Imagine and ArcMap IMG files).

thanks

mike

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  • global_mapper
    global_mapper Administrator
    edited January 2008
    Global Mapper should auto-detect invalid (void) samples and treat them as transparent without you having to specify anything. Are the void areas not showing up as transparent when you load the data into Global Mapper?

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • miksmith
    miksmith Global Mapper User Trusted User
    edited January 2008
    Hi Mike

    Strangely I didn't actually test it in GM, however when the export to 32-bit elevation ERDAS files, the Null Data tagging seemed to have disappeared (when they were loaded in to either ArcMap or Imagine). Double checking, yes the transparency does work fine for the imported ASCII GRID files.

    As an aside:

    -is there an inquire cursor tool?
    -is there a way of directly viewing the pixel values in an array? (and by specifying a box on the screen would be great!)

    Grid file attached

    ta

    m
  • global_mapper
    global_mapper Administrator
    edited January 2008
    GM does not write out the null value tag to generated Erdas Imagine files as our Erdas support library does not yet know how to write that out. By default a value of -9999 will be used for no data areas written out to Erdas Imagine format files.

    I suppose that the Feature Info tool could be considered an inquire cursor tool. Is this what you are after?

    There is not currently a way to directly view pixel values in an array.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • miksmith
    miksmith Global Mapper User Trusted User
    edited January 2008
    Hi Mike

    Thanks for the explanation. I think the Null Data support only came in in the last version (although Im not sure how robust it is. ArcMap tends to be much better). Do you have a list of which formats support Null Data??

    thanks

    mike
  • global_mapper
    global_mapper Administrator
    edited January 2008
    Global Mapper supports either explicitly provided or implicit null-data values from all elevation formats on import. Some of the formats that provide explicitly listed null data values on export are:

    Arc ASCII Grid
    BIL
    DEM

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com

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