NSRS 2007 Projection

jh93989jh93989 Global Mapper UserPosts: 41Trusted User
edited July 2014 in Projection Questions
Good Morning,

We use NSRS2007 MD (EPSG:3582) quite a lot; however, when LiDAR files set with this projection are pulled in to GM they always show up as EPSG:2248. Is there something that can be done to address this discrepancy? Possibly adding support for the NSRS2007 projections?


GM_Proj.jpg

Thanks,
Jameson

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited July 2014
    Jameson,

    I have added the NAD83 (NSRS2007) datum to Global Mapper, although for now it behaves as synonymous to normal NAD83. In reality it might be up to a few centimeters different, but I haven't found a transformation grid file yet. Apparently ESRI does the same thing and doesn't actually transform it. At least now the datum will list correctly and get the correct EPSG code, just know if you convert to another datum it will behave exactly like NAD83.

    I have placed new builds with the latest changes at the links below:

    32-bit: http://www.bluemarblegeo.com/downloads/global-mapper/global_mapper15.zip
    64-bit: http://www.bluemarblegeo.com/downloads/global-mapper/global_mapper15_64bit.zip

    Simply download the .zip file for the build that you are using and extract over your existing installation files. The likely locations to extract to are as follows:

    32-bit: C:\Program Files (x86)\GlobalMapper15
    64-bit: C:\Program Files\GlobalMapper15_64bit

    Thanks,

    Mike
    Global Mapper Guru
    geohelp@bluemarblegeo.com
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
  • jh93989jh93989 Global Mapper User Posts: 41Trusted User
    edited July 2014
    Thanks Mike, I was aware there were no real transformations, I was mostly looking to add it this to the header for the projection information.

    Semi-Related, would it be possible to thin out what geokeys are added to the las header? There seems to be a lot of clutter, we only use the below keys.
    key 1024
    key 3072
    key 3076
    key 4099
    key 4096

    Also, the 2nd and 3rd VLR seem to be extraneous as well but I'm sure you guys have a reason for that. I've attached a text file of the current header output.test4_info.txt

    Might be wishful thinking but it never hurts to ask!
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited July 2014
    All of those keys are present so reading software can determine the geo-reference regardless of what keys they look for. Some software uses different keys than others, so Global Mapper just writes them all. You can of course just ignore the keys you don't care about. The 2nd and 3rd variable length records are for the GeoTIFF double-precision and ASCII text tags. If you are always using the EPSG code you don't need those, but if the file uses a projection that doesn't have an ESPG code, the full definition of the projection will be in the double-precision tags, as will the full ellipsoid definition.

    Thanks,

    Mike
    Global Mapper Guru
    geohelp@bluemarblegeo.com
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited July 2014
    If you export a LAS v1.4 file you also get an extended variable length record with the WKT projection string which is much easier to parse than all of the GeoTIFF tags.

    Thanks,

    Mike
    Global Mapper Guru
    geohelp@bluemarblegeo.com
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
  • jh93989jh93989 Global Mapper User Posts: 41Trusted User
    edited July 2014
    Great answers Mike, thank you for clearing that up for me.
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