Files revert to original projection

daver819daver819 Global Mapper UserPosts: 28Trusted User
I have some files that were originally exported in UTM projection. I need to break them apart and put them in Geographic projection. I loaded the original file and reprojected it to geographic. then I selected the polygons I wanted to break out and pasted them into another window of Global mapper. When I pasted them into the new windo with nothing else open , they reverted to UTM. I am running version 16.2

Answers

  • bmg_bobbmg_bob Global Mapper Programmer Posts: 2,058
    Changing the projection using the Configuration dialog changes the projection used to display the data, but does not change the projection of the underlying data. Then when you copy features and paste them to another instance of Global Mapper, they will be displayed using the second instance's currently active projection (or in the pasted data's native projection, if the it is the first to be loaded.) In your case, since the second instance had no data loaded, the pasted features were displayed in UTM, which is their native projection. Once you change the projection in the second instance to Geographic, any additional data you paste into that instance will be displayed that way. If you want to change the native projection of the data, you should export it.
  • MykleMykle Global Mapper User Posts: 446Trusted User
    Dave,
    Files/images remain in their projection as loaded into Global Mapper.
    Each file can be loaded with a different projection.
    Your DISPLAY projection is independent of the projection(s) of the loaded layer(s).

    The initial DISPLAY projection will be set to the projection of the your first set of data. So, your new window should be set to UTM since that is the projection of your first data. Again, set the DISPLAY to whatever you like.

    EXPORTED files will use the current DISPLAY projection. Again, reset to suit your needs. When an exported file is loaded, it will use the same projection as it was exported (check the metadata).

    So, it is often useful to export files that you have loaded. Exported layers may be set to a different projection, they may be cropped, they may be combined with other layers, whatever.

    Most data downloaded from internet sources will allow export to local files, at least so that loading them into your current or future project does not require downloading again. An example is elevation data.

    Some file formats have advantages over others. Elevation data is more efficient in terms of filesize and speed when using the Global Mapper Elevation format (GMG file).

    Cheers,
    Mykle
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