Global Mapper v25.0

Exported GeoTIFF Images are Larger

adruf
adruf Global Mapper UserTrusted User
edited February 2015 in Technical Support
Hi, I'm using Global Mapper v14.2 on Windows 7 64bit, and I'm having issues with exporting GeoTIFFs. Here's my process: I have to download Tax Maps for our county, load them all into Global Mapper and export them with a different grid and naming convention (one that matches our internal datasets) than the original index grid they come with. Seems simple enough of a process, but it's been a problem. I'm finding that during the export process some of my GeoTIFFs images are 3 times the original .tif dimensions. No other issues, but I don't know what could be causing the images to tripple their pixels in size.. any ideas?

Thanks!

Comments

  • adruf
    adruf Global Mapper User Trusted User
    edited February 2015
    Let me add that the new index grid that I'm using to export all of these compiled tifs is not MUCH different than the original grid and in many places it's exactly the same as what's provided.
  • tjhb
    tjhb Global Mapper User Trusted User
    edited February 2015
    Are all of your source images at the same pixel resolution? I.e. the same number of metres/feet per pixel.

    If you are exporting a mixed-resolution dataset all at once, then by default GM will give every export the resolution of the finest source image.
  • notsofast
    notsofast Global Mapper User
    edited February 2015
    I'd like to jump in on this topic with what might be a related question.

    I am trying to export raster tiles from a large input dataset. The output grid origin, output tile size, and output pixel GSD are all fixed and cannot vary. I am having some difficulty keeping those values fixed using the EXPORT_RASTER script command.

    Here is an example. As you can see, the output GSD I am going for is 0.1 m. My grid needs to stay aligned with the origin specified by GLOBAL_BOUNDS_SIZE, but when I add a crop polygon (see the last two lines) it shifts the tile grid to align with the top and left of the polygon. How can I prevent that from happening? How can I keep the tile grid constant and control which tiles are output based on a polygon?

    EXPORT_RASTER \
    FILENAME="cropped/tile.tif" \
    TYPE=GEOTIFF \
    SAMPLING_METHOD=AUTO \
    GLOBAL_BOUNDS_SIZE="230073.0,2703157.0,409.6,409.6" \
    PIXEL_SIZE="4096x4096" \
    QUALITY="100" \
    BG_TRANSPARENT=YES \
    COMPRESSION=NONE \
    // GRID_TYPE_CELL_SIZE="102.4,102.4" \
    GRID_TYPE_PIXEL_SIZE="1024,1024" \
    GRID_TYPE_ROWS_COLS="4,4" \
    GRID_NAMING=SEPARATE \
    GRID_NAMING_COLS="NUM,0,c,1" \
    GRID_NAMING_ROWS="NUM,0,r,1" \
    GRID_NAMING_PREPEND_ZEROES=YES \
    GRID_NAMING_SEPARATOR="-" \
    GRID_CREATE_FOLDERS=YES \
    POLYGON_CROP_FILE="cropPoly.shp" \
    POLYGON_CROP_USE_ALL=YES
  • tjhb
    tjhb Global Mapper User Trusted User
    edited February 2015
    I'm not certain this will do it, but try setting these options true (under Tools>Configuration>General>Miscellaneous advanced options).
    • Export: Snap Export Bounds to Pixel Boundary if Possible - When this option is checked the bounding box for an export will be adjusted so that the top left corner of the bounding aligns with the top left corner of a pixel in the imagery being exported. This is useful to eliminate any visual sub-pixel shift due to mis-alignment of the export bounds and the pixels in the input imagery.

    • Export: Keep Pixel if any Part is Inside Crop Area - When this option is checked and you are cropping a raster/elevation export to a selected area feature, an exported pixel/cell will be kept if any corner of that cell is within the crop area rather than the default requirement of the center of the cell being in the crop area.