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gridding method / moon data

thomas krügerthomas krüger Global Mapper UserPosts: 7 ✭✭
edited October 2010 in Elevation Data
i am fiddling arround with a set of moon elevation data. the data acquisition resulted in longitudinal (pole to pole) rows of high density xyz-readings.
after loading part of this dataset in gm the resulting presentation (orthographic projection) shows very well the main structures (see attachment). however i am puzzled about the scattered radial irregularites which seam to display much of the data acquisition pattern rather than a smooth surface i would expect given the high data density.

is that possibly due to the built in gridding algorithms? grateful for some ideas?

data-sample.jpg
data-sample.jpg
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Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238BMG Staff
    edited October 2010
    Do those irregularities appear if you view in other projections, like maybe a polar stereographic or just a local one like Transverse Mercator? If you turn off hill shading are the streaks still there?

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • princessprincess Global Mapper User Posts: 1 ✭✭
    edited October 2010
    im gerade neu in diesem Forum....
  • thomas krügerthomas krüger Global Mapper User Posts: 7 ✭✭
    edited October 2010
    hello mike,
    thanks for your reply. different projections as suggested dont eliminate the observed phenomena. also turning off hill shading has no effect (see attachment).
    in meantime i got a chance to visually check the data structure in 3d of another set off elevation readings in this case with a dense circular alinement of data points in the polar region. attached graphic shows this arrangement which demonstrates an extreme density along the recording tracks and hardly any data inbetween. a balanced interpolation should level the symetrical linewise aggregation of data. my suspicion is that this is the main cause for the observed irregularities!?

    regards
    pole-data-byrd-shading-off.jpg
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    data-pattern.jpg
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  • global_mapperglobal_mapper Administrator Posts: 17,238BMG Staff
    edited October 2010
    Yes the arrangement of the data is likely the cause of the issue as the triangulation formed from those data points would be dense inside the bands and then have stretched triangles in between. You might try reprojecting the raw 3D point data prior to generating the elevation grid to see if you can avoid the stretched triangles along radials, although you will still get some artifacts in the areas of no data since there will just be linear interpolation within those region to guess at the actual elevations without any actual data samples in those areas.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • thomas krügerthomas krüger Global Mapper User Posts: 7 ✭✭
    edited October 2010
    thanks so far. i will let you know what ultimate solution i could dig up...

    regards thomas
  • MattMatt Global Mapper User Posts: 176Trusted User ✭✭
    edited October 2010
    Weird things happen as you get near the poles. I think that's just a function of the way the original data was collected.
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