Georeferencing prob (mapmart to global mapper to bing tiles)

kirkbkirkb Global Mapper UserPosts: 12Trusted User
Here's the workflow I'm trying to establish:

- Buy a map from mapmart (TIFF + TFW + metadata)
- Convert TIFF to JPG; perform artistic additions/enhancements
- Rename TFW to JPW
- Import JPG + JPW into Global Mapper 11.02
- Manually select projection and datum. Mapmart says: UTM, Zone 18, NAD83
- Export to bing tiles

When I view the bing results (tiles overlaid onto road map), I can see that the tiles are shifted a couple hundred meters too far south. Same thing happens when I export to google tiles. Ditto if I import an Openstreet layer into the project.

Any idea what's going on?

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited July 2010
    It sounds like somewhere the projection is not set correctly or something else is changing. Your not resizing the image when converting to JPG are you? If you just load the TIFF directly into Global Mapper and bring in some other data source (like OpenStreetMaps or DigitalGlobe imagery) is the data lined up then? If not then the projection or datum that you are initially choosing when loading the data is the issue. For a shift of a few hundred meters the datum sounds like the likely culprit. Is there any information about this in the metadata file accompanying the TIFF?

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • kirkbkirkb Global Mapper User Posts: 12Trusted User
    edited July 2010
    Yes, I think the TIFF was resized when it was converted to JPG. Aspect ratio was preserved, though.

    The content of the metadata is pretty simple:

    Project Number: MapMart #xxxxxxxx
    Date Collected: 09-02-09
    Projection: UTM Zone 18 North
    Datum: NAD83
    Pixel Size: .6 meters
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited July 2010
    Resizing the JPG file will make the TFW coordinate values no longer correct as they describe the mapping from pixel coordinates in the image to ground coordinates. If you resize the JPG you will have to modify the values in the world file as well (just the pixel size parameters, assuming the top left corner stays at the same location). For example if you double the pixel dimensions of the JPG file, you would halve the pixel size values in the world file. See http://en.wikipedia.org/wiki/World_file for a description of the world file format. The 1st and 4th lines are what you would change.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • kirkbkirkb Global Mapper User Posts: 12Trusted User
    edited July 2010
    That seems to do the trick with "guesstimated" files. I'll go find the exact sizes of the original TIFF and the new JPG so I can calculate the exact size.

    Thanks!

    BTW, if my output image ends up being off by a few yards because of problems with the accuracy of the original satellite image, is there a way to manually shift it by a specified amount?
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited July 2010
    Yes, you can right-click on a layer in the Control Center and there will be an option to shift it by a fixed amount, in addition to one to manually reposition the layer which allows for full rectification.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • kirkbkirkb Global Mapper User Posts: 12Trusted User
    edited July 2010
    There's no way to fully automate the process of importing a JPG/JPW and exporting bing tiles, is there?

    It would be a nice way for me to process dozens/hundreds of maps without having to do it manually.
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited July 2010
    You can't automate that directly in Global Mapper using a script or anything, although if you are a bit of a programmer you can do so using the Global Mapper SDK as it supports web format exports. See the Developers page at http://www.globalmapper.com for more details.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
Sign In or Register to comment.