Antarctica Spherical Projection

sant0ssant0s Global Mapper UserPosts: 13Trusted User
edited June 2014 in Projection Questions
Hi,

is there a world projection method, that moves the antarctica to its "normal" shape?
Actually like the mercator projection where the antarctica is not at the bottom but in the middle of the image.
Or can I move the texture like its mapped on a sphere?

edit: pole shift? is that what I have to do? and if, how? :)

Thank you!
sant0s

Comments

  • sant0ssant0s Global Mapper User Posts: 13Trusted User
    edited June 2014
    just to get a better idea what I mean:

    Google-Ergebnis für http://i41.tinypic.com/2h6y1dj.jpg

    greatings :)
  • sant0ssant0s Global Mapper User Posts: 13Trusted User
    edited June 2014
    just to get an idea, what I mean. something, where the antarctica is the middlepoint of the map.

    http://oi41.tinypic.com/2h6y1dj.jpg

    source: xkcd ? View topic - 0977: "Map Projections"

  • sant0ssant0s Global Mapper User Posts: 13Trusted User
    edited June 2014
    oh and i tried this: http://www.globalmapperforum.com/forums/technical-support/7041-antarctic-projections.html

    but even when I change the true scale parameter, I cannot get the antarctica on top.

    and sry for adding new posts, but somehow I cannot edit the older post's.
  • Jasmine_BMGJasmine_BMG BMG Staff Posts: 174
    edited June 2014
    Hello Sant0s,

    Have you tried the UPS (Universal Polar Stereographic) Projection in Global Mapper?

    Regards,

    Jasmine
  • sant0ssant0s Global Mapper User Posts: 13Trusted User
    edited June 2014
    hey jasmin,
    thy for your answer.
    seems to come close, will try to wrap that (north and sout?!) somehow around a sphere.
    right now I work with two images. its working, but if there is a more accurate way where I do not have to fit the antartica on another map, would make life more easy :)

    globes_test.jpg
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited June 2014
    You might also try using the 'Vertical Near-Side Perspective' projection which is basically the earth if looking directly down on it from an altitude over some lat/lon. Try a very large height, like 50000000 to see the entire hemisphere. Set the Central Longitude and Central Latitude to the location you want centered on, like -90 for the Central Latitude to have Antarctica in the center.

    Thanks,

    Mike
    Global Mapper Guru
    geohelp@bluemarblegeo.com
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
  • Ice Age MarkIce Age Mark Global Mapper User Posts: 294Trusted User
    edited June 2014
    sant0s,

    There is also the Orthographic Projection, with the Lat/Long set for the place you want to view from (e.g. -40,-90), and the rotation angle set to 180 degrees; like the attachment showing today's sea ice extent around Antarctica.

    Mark
  • sant0ssant0s Global Mapper User Posts: 13Trusted User
    edited June 2014
    thanks alot, guys!
    Both seems to be quite similar.

    @Ice Age Mark:
    What projection did you use on that sphere to get it seamless? did you stitch both outputs (south and north) together in Photoshop or directly in an GIS app? And my outputs are streched to the borders, how can i avoid that? Your image looks quite clean. :)

    Oh and whats the name of the imagery you are using on that sphere? looking interesting since we also have to animate sea ice extent...

    sant0s
  • Ice Age MarkIce Age Mark Global Mapper User Posts: 294Trusted User
    edited June 2014
    sant0s,


    No Photoshop or stitching, this is real gridded elevation data.


    The global base map is the GEBCO gridded data set available here:


    GEBCO gridded bathymetry data


    The projection is Orthographic with a rotation of 180 degrees.


    You can get the SH sea ice to load over it with this script that contains the URL, control points, etc:


    GLOBAL_MAPPER_SCRIPT VERSION="1.00" FILENAME="X/X/X.gmw"
    SET_BG_COLOR COLOR="RGB(0,0,0)"


    DEFINE_PROJ PROJ_NAME="PS_WGS84"
    Projection POLAR
    Datum WGS84
    Zunits NO
    Units METERS
    Xshift 0.000000
    Yshift 0.000000
    Parameters
    0 0 0.000 /* longitude_pole


    -90 0 0.000 /* latitude of true scale


    0.000 /* false easting (meters)


    0.000 /* false northing (meters)


    END_DEFINE_PROJ
    IMPORT FILENAME="ftp://polar.ncep.noaa.gov/pub/ice/sh12.gif"; \
    TYPE="GIF" PROJ_NAME="PS_WGS84" RECTIFY="Polynomial" GCP="Point 1,690.0823109,-0.1335583,-3746674.2940214,6023970.0370387" \
    GCP="Point 2,-0.0630879,-0.0365115,-5374133.0013230,-3198543.2409366" GCP="Point 3,-0.2250353,709.9867565,4116028.5049057,-4872386.6754994" \
    GCP="Point 4,690.1762560,710.0111462,5743326.0542764,4349949.7210586" LABEL_FIELD_FORCE_OVERWRITE="NO" \
    SAMPLING_METHOD="BICUBIC" LAYER_DESC="LATEST SH SEA ICE" AUTO_CONTRAST="NO" CONTRAST_SHARED="YES" CONTRAST_MODE="NONE" \
    CLIP_COLLAR="NONE" TEXTURE_MAP="NO" TRANSPARENT_COLOR="RGB(0,0,0);RGB(127,127,127);RGB(255,191,255);RGB(255,232,255);RGB(255,255,255)"


    Good luck,


    Mark
  • Ice Age MarkIce Age Mark Global Mapper User Posts: 294Trusted User
    edited June 2014
    sant0s (and anyone),


    You can easily add GEBCO to your GM online sources with this URL:


    http://www.gebco.net/data_and_products/gebco_web_services/web_map_service/mapserv


    For some good data sets of Antarctica (like the attached, with the ice removed) go to:


    Antarctic Digital Database version 6.0


    You have to register to download, but it's easy.


    Mark
  • sant0ssant0s Global Mapper User Posts: 13Trusted User
    edited June 2014
    hey mark, thx alot! :)
    Dont know why, but behind the wms url is a "?" missing, otherwise I get an error after choosing the grid.
  • sant0ssant0s Global Mapper User Posts: 13Trusted User
    edited June 2014
    one more question a bit off Topic: what do I have to look for, if I would like to see the arctic ice "growing" and "shrinking" inside Global Mapper and could I render something like that as an sequence?
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited June 2014
    You could perhaps script something like that where you load one date, export to a file, then unload that and load the next date, etc. You would use the DIR_LOOP_START...DIR_LOOP_END to loop over the files, then IMPORT, EXPORT_RASTER, and UNLOAD_LAYER inside the loop. See Global Mapper Scripting Reference for details.

    To do this inside the user interface, you would great a separate group of layers in the Control Center for each date, then turn off all but one group to see just one date. To switch dates, just turn off that date and turn on the next one.

    Thanks,

    Mike
    Global Mapper Guru
    geohelp@bluemarblegeo.com
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
  • Ice Age MarkIce Age Mark Global Mapper User Posts: 294Trusted User
    edited June 2014
    The only way I can think of would be to get the "bedmap2" dataset from SCAR and use that. It has an elevation Geotiff of the present surface, the 'no-ice' surface (used for my screenshot), and a 'thickness' layer. The 'no-ice' surface was likely produced by simply subtracting the thickness layer from the surface layer. You could sequentially modify (shrink) the ice thickness layer using some formula in the raster calculator (but for elevation data), re-subtract each one from the present surface, and produce a series from that to use, say in a PowerPoint animation.


    Best of luck,


    Mark
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