Merging and exporting geotiffs without extra pixels/data?

I am essentially exporting geotiffs on global mapper and putting them on a GPS unit.
I am experiencing a lot of lag on the unit wherever the maps overlapped (can't see this, but looking at the maps on global mapper it is easy to tell). I merged the maps but am still experiencing the exact same problem in the areas where they USED to be overlapped. Anyone have an idea why I am still  experiencing this issue? It's as if when global mapper merges the geotiffs it is still exporting double the pixels/data where the overlapped area was. 

I even tried cropping the maps alone and using them, cropping them and then merging them, and still the same issue. Ideas? Thank you!!

Answers

  • bmg_bobbmg_bob Global Mapper Programmer Posts: 1,834
    When you say that you merged the maps, do you mean that you loaded multiple GeoTIFFs into Global Mapper, then exported a single GeoTIFF?  When exporting a raster file, Global Mapper only includes one value for each pixel -- usually the value from the topmost layer in the draw order -- so there is no extra data where the images overlapped.  Did you remove the old images from the GPS device before putting the merged image on?  Is it possible that the GPS is lagging because there are multiple images loaded that cover the same area?

    What version of Global Mapper are you using?
  • tdashtdash Posts: 7
    Yes, that is exactly how I exported them. That's logical (one value for each pixel)... thank you!

    Yes, I have removed the old images, they are not the issue. 

    I am using global mapper 14. Any other ideas?

    I know my unit could be responsible as well (perhaps the merged image is too large for it to handle..?) so I just want to determine if it is a global mapper issue or gps unit issue. 
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