Global Mapper v25.0

Gridded export of an Elevation File

PeterDrexel
PeterDrexel Global Mapper UserTrusted User
edited March 2013 in Bug Report
Mike
in GM 13.2 and 14.1 if I export a .img-Elevation-Modell to Arc Ascii Tiles using Gridding based on a Shapefile containing rectangles (10000x10000 m) I get asciifiles like this one (which is perfect):

ncols 10000
nrows 10000
xllcorner -45000
yllcorner 275000
cellsize 0.0
nodata_value -9999.0
-9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0
....


if I want the Files to Overlap say 1% I choose Oberlap Grid Cells by 1 % (100m in all directions) then I get the following result:

ncols 10200
nrows 10200
xllcorner -45049.995
yllcorner 274950.005
cellsize 0.499999019512
nodata_value -9999.0
-9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0
...

the xllcorner / yllcorner - Values are both of by 5mm and the Cellsize is also wrong.
It must look this way:

ncols 10200
nrows 10200
xllcorner -45050
yllcorner 274950
cellsize 0.5
nodata_value -9999.0
-9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0
....

I need the exact kkordinates, because later in the process-chain I recombine buffered (overlapping) Grids with non-overlapping Grids and get wrong results!
Thanks
Peter

Comments

  • global_mapper
    global_mapper Administrator
    edited March 2013
    Peter,

    I took a look and discovered that the overlap when doing an elevation export wasn't calculating the X and Y spacing correctly. I have fixed that now. I have placed a new build at http://www.bluemarblegeo.com/downloads/global-mapper/global_mapper14.zip with the latest changes for you to try. Simply download that file and extract the contents into your existing v14.xx installation folder to give it a try. If you are using the 64-bit v14 version there is a new build at http://www.bluemarblegeo.com/downloads/global-mapper/global_mapper14_64bit.zip .

    Thanks,

    Mike
    Global Mapper Guru
    gmsupport@bluemarblegeo.com
    http://www.bluemarblegeo.com/
  • PeterDrexel
    PeterDrexel Global Mapper User Trusted User
    edited March 2013
    Mike,
    I habe updated the Programm, but it seems it still does not work correctly...

    Without overlapping I get
    ncols 10000
    nrows 10000
    xllcorner -45000.000
    yllcorner 275000.000
    cellsize 0.5
    nodata_value -9999.0
    -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 ...

    with overlapping 1 pix (50cm)I get
    ncols 10002
    nrows 10002
    xllcorner -45001.000
    yllcorner 274999.500
    cellsize 0.500049995
    nodata_value -9999.0
    -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 ...

    ...xllcorner and cellsize are wrong, should be -45000.500 / 0.5

    with overlapping 100 pixel (50m) I get
    ncols 10200
    nrows 10200
    xllcorner -45050.500
    yllcorner 274950.000
    cellsize 0.500049024414
    nodata_value -9999.0
    -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0 -9999.0

    ...xllcorner and cellsize are again wrong, should be -45050.000 / 0.5.

    Thanks
    Peter
  • global_mapper
    global_mapper Administrator
    edited March 2013
    Peter,

    Do you perhaps have the option checked to maintain export bounds over spacing in the Advanced section of the General tab of the Configuration dialog? That could cause what you are seeing. In my tests the adjustment is correct without that option checked.

    Thanks,

    Mike
    Global Mapper Guru
    gmsupport@bluemarblegeo.com
    http://www.bluemarblegeo.com/
  • PeterDrexel
    PeterDrexel Global Mapper User Trusted User
    edited March 2013
    Mike,
    still the same Isue:
    I dit upload you my Sampledata here:
    ftp://ftp_lvauser:!ftpdownload@ftp.vorarlberg.at/Peter/gm.zip

    so I hope you can now reproduce the isue:

    What i dit:
    I did run GM 14.1 64 bit Build jan 30 2013
    I dit update with the provided .zip - (some of the provided Files in the zip were older then the already installed Build jan 30 2013-Files ie QuickPDFDLL.DLL etc.).
    I dit restore to the Default Settings in the General-Tab of the Configuration.

    The Archive contains

    5000er.shp: The Boundry-Shape auf the "Big" Elevation Grid I want to clip (gt_5m12255000.asc)

    1000er.shp: The Boundry-Shape auf the "Smal" Elevation Grid I want to create.

    gt_5m_exact_1225092.asc: The Grid I get when I just Export Elevation Grid Format ArcAscii - Gridding - Use Selected Area Features - no Overlap - Select Grid Cell Naming "V1_NR_TXT" - Crop = NO.
    -> Perfect Result:
    GM Metadata:
    FILENAME=D:\gm\gt_5m_exact_1225092.asc
    DESCRIPTION=gt_5m_exact_1225092.asc
    UPPER LEFT X=-39372.500 (is the Center of the Pixel)
    UPPER LEFT Y=248997.500 (is the Center of the Pixel)
    LOWER RIGHT X=-38752.500 (is the Center of the Pixel)
    LOWER RIGHT Y=248502.500 (is the Center of the Pixel)
    WEST LONGITUDE=9° 48' 42.8103" E
    NORTH LATITUDE=47° 22' 45.1199" N
    EAST LONGITUDE=9° 49' 12.5248" E
    SOUTH LATITUDE=47° 22' 28.9570" N
    PROJ_DESC=Austrian Grid / AUSTRIA / meters
    PROJ_DATUM=MGI AUSTRIA
    PROJ_UNITS=meters
    EPSG_CODE=31254
    COVERED AREA=0.3069 sq km
    NUM COLUMNS=125
    NUM ROWS=100
    PIXEL WIDTH=5 meters
    PIXEL HEIGHT=5 meters
    MIN ELEVATION=1078.56 meters
    MAX ELEVATION=1269.34 meters
    ELEVATION UNITS=meters
    BIT_DEPTH=24

    -> Extent is 625x500m ranging from -39375/249000 to -38750/248500
    -> Lower Right x - Upper Left x = 620 (perfect)
    -> Upper Left Y - Lower Right y = 495 (perfect)

    ASCII-File:
    ncols 125
    nrows 100
    xllcorner -39375.000
    yllcorner 248500.000
    cellsize 5
    nodata_value -9999.0
    1078.6 1079.62 1080.33 1081.48 1082.82 1086.45 1086.53 1088.95 1090.78 1093.34 1094.65 1096.23 1097.63 1099.92 ...

    ______________________________________



    gt_5m_1pix_default_1225092.asc: The Grid I get when I use Export Elevation Grid Format ArcAscii - Gridding - Use Selected Area Features - 1 pix Overlapp - Select Grid Cell Naming "V1_NR_TXT" - Crop = NO.
    -> Result:
    GM Metadata:
    FILENAME=D:\gm\gt_5m_1pix_default_1225092.asc
    DESCRIPTION=gt_5m_1pix_default_1225092.asc
    UPPER LEFT X=-39382.500
    UPPER LEFT Y=249007.500
    LOWER RIGHT X=-38747.500
    LOWER RIGHT Y=248497.500
    WEST LONGITUDE=9° 48' 42.3304" E
    NORTH LATITUDE=47° 22' 45.4448" N
    EAST LONGITUDE=9° 49' 12.7647" E
    SOUTH LATITUDE=47° 22' 28.7929" N
    PROJ_DESC=Austrian Grid / AUSTRIA / meters
    PROJ_DATUM=MGI AUSTRIA
    PROJ_UNITS=meters
    EPSG_CODE=31254
    COVERED AREA=0.3239 sq km
    NUM COLUMNS=127
    NUM ROWS=102
    PIXEL WIDTH=5.04 meters
    PIXEL HEIGHT=5.05 meters
    MIN ELEVATION=1076.25 meters
    MAX ELEVATION=1271.2 meters
    ELEVATION UNITS=meters
    BIT_DEPTH=24

    -> Extent should now be 635x510m ranging from -39380/248995 to -38745/248505 (Overlapp is 1pix in all directions)
    -> Lower Right x - Upper Left x = 635 (should be 630 as the coodinates are of Pixel-Center)
    -> Upper Left Y - Lower Right y = 510 (should be 505 as the coodinates are of Pixel-Center)

    ASCII-File:
    ncols 127
    nrows 102
    xllcorner -39385.020
    yllcorner 248494.975
    xdim 5.039682539683
    ydim 5.049504950495
    nodata_value -9999.0
    1076.25 1077.25 1078.44 1080.44 1081.57 1082.58 1083.86 1086.77 1087.15 1089.4 1090.73 1093.37 ...

    the
    xllcorner should be -39380 (is the ll of the pixel and not the center)
    yllcorner should be 248495 (is the ll of the pixel and not the center)
    the xdim and the ydim both should be 5
    When I multiply the (nrows-1) with ydim I get 510
    When I multiply the (ncols-1) with xdim I get 635



    The resulting overlapping grid is 5m to wide and 5m to high,
    The Overlapp in the Lower Right Corner is fine, but in the Upper Left Corner it is 10/10m.

    Thanks
    Peter
  • global_mapper
    global_mapper Administrator
    edited March 2013
    Peter,

    Ah ok I see now, it was the gridding to a selected area with overlap where the mis-calculation was and I wasn't doing that step. It was treating the bounds as display vs. grid cell center bounds when doing the overlap for that particular case. I have fixed that now and seem to get the same results you are after. I have placed a new build at http://www.bluemarblegeo.com/downloads/global-mapper/global_mapper14.zip with the latest changes for you to try. Simply download that file and extract the contents into your existing v14.xx installation folder to give it a try. If you are using the 64-bit v14 version there is a new build at http://www.bluemarblegeo.com/downloads/global-mapper/global_mapper14_64bit.zip .

    Thanks,

    Mike
    Global Mapper Guru
    gmsupport@bluemarblegeo.com
    http://www.bluemarblegeo.com/
  • PeterDrexel
    PeterDrexel Global Mapper User Trusted User
    edited March 2013
    Mike,
    works now, good job!
    Thanks
    Peter