Map Scanning & Importing

acgardiner
acgardiner Global Mapper UserTrusted User
edited May 2008 in Technical Support
There no longer appears to be a source of 1,000,000 topographical maps in Canada. I have a few old ones and wondered if I had them scanned would it be possible to import them into GM so that adjacent maps can be lined up with each other? Right now I use the "Automatically Crop DRG-style Collar" function to line up ETopo pre-calibrated 1:50,000 and 1:250,000 maps that I've purchased. Should I get them scanned in TIF, JPG, PNG, PDF, etc. format?

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  • global_mapper
    global_mapper Administrator
    edited May 2008
    Yes you should be able to scan your data and then load it into Global Mapper using the File->Rectify Imagery menu command and provide control points to get the data properly positioned. You should then be able to crop the collar using the normal mechanism.

    I would recommend the TIF or PNG formats for scanned topographic maps.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • acgardiner
    acgardiner Global Mapper User Trusted User
    edited May 2008
    Mike,

    I have had Staples scan two 1:1,000,000 topographical maps into PNG files. They are adjacent maps, i.e. one is due east of the other. One file is 150 Mbytes and the other 100 Mbytes. I am having great difficulty calibrating them so that I can get a seamless connection of the two maps, cropping to manually specified lat/lon. Is it because the files are two large to work with?

    Tony
  • global_mapper
    global_mapper Administrator
    edited May 2008
    Tony,

    For PNG files that large, the files are being decompressed to disk and read from there on-the fly to save memory usage. This could slow things down, particularly at load time or if your Temp directory is on a slow disk. You might try converting your PNG files to TIFF files and see if those are faster as they can be directly read from disk on the fly and don't require a temporary file.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • global_mapper
    global_mapper Administrator
    edited May 2008
    For seamless cropping, make sure that the lat/lon borders of the map align on even lat/lon boundaries. It is possible that they are aligned to a UTM grid or something like that.

    Another option for cropping is to crop to a polygon. You can draw an area feature that exactly goes down the borders of a map, then select it with the Digitizer Tool, then open the Control Center, select the layer to crop, press Options, then go to the Feathering tab and select to crop to the selected area, then specify a crop pixel distance of just 1 pixel to just do a crop and no feathering.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • acgardiner
    acgardiner Global Mapper User Trusted User
    edited May 2008
    I'm still having trouble calibrating the two maps but I notice when I bring them into GM true north is to the right of the screen. Would that inhibit the process? Also these two maps are Lambert Conformal Conic Projection. Do I need to correct for that?
  • global_mapper
    global_mapper Administrator
    edited May 2008
    For projections like Lambert Conformal Conic, true north will only be straight up at the centeral meridian of the projection. To make true north always be up, you'll need to view your data in a projection like Mercator, Geographic, or Robinson.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com

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