dataset between 0 and 360 degrees

TibTib Global Mapper UserPosts: 9
edited June 2013 in Projection Questions
Hi,

I have a problem which looks simple but I can't find any easy way to solve it.

I have a planetary dataset which is located between 0 and 360 degrees (geographic coordinates). I'd like to convert it so it would be between -180 and 180 degrees.

For now the only way I found to do it, is to cut the part which is between 180 and 360 and modify the header (in BIL file) so that origin becomes -180 instead of 180. And then put the 2 parts together again.

If I do this, I can see the 2 parts (left and right) at the good place in global mapper, but if I want to export the 2 parts, only right part is exported.


Is this the good way to do it?, is there an easier way to do it with global mapper or gdal?

Thank you!

Thibaud

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited June 2013
    Thibaud,

    Yes you can fix this in Global Mapper. Just set the native projection for the layer to Geographic with a Central Longitude of 180. That means it goes from 0 to 360. Then go to the Projection tab of the Configuration dialog and make the Central Longitude of the view projection 0. This should automatically make it go from -180 to +180. You can then export to a single new file.

    Thanks,

    Mike
    Global Mapper Guru
    geohelp@bluemarblegeo.com
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
  • TibTib Global Mapper User Posts: 9
    edited June 2013
    Thank you Mike,

    It looks like it's working!

    However, I have an interesting side effect: when I open my data (with the central longitude of 180) I have a resolution of (0.0078125,0.0078125).

    And after changing the central-longitude to 0, the resolution becomes: (0.00158227848101266,0.0078125). So I had to manually set the resolution back to (0.0078125,0.0078125) to avoid having my file getting much bigger.


    Thibaud
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