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Martin: I am working the GOES-R program (next generation geostationary weather satellite program). It is our plan to generate CF convention compliant NetCDF product files that are projected from the idealized scanning imager on the satellite. We had thought the vertical perspective was the appropriate projection. I went back and read through the "vertical perspective projection" in John Snyder's document (Map projections- A Working Manual), and it it unclear why this existing projection in the CF conventions is not applicable. It is true that the GOES-R satellite imager (i.e. camera) does not precisely faces the center of the Earth because it is scanning in approximately 500 km N-S swaths from west to east, but I am confused how this characteristic changes the projection geometry. Could you augment the explanation you have already provided ? very respectfully, randy ---------- Original Message ---------------------------------- From: Martin Raspaud <martin.raspaud@xxxxxxx> Date: Tue, 22 Nov 2011 13:28:32 +0100 >-----BEGIN PGP SIGNED MESSAGE----- >Hash: SHA1 > >Hi all, > >There seems to be a need from the weather satellite folk to add the >"geos" projection to the list of projections in the CF metadata. > >"geos" stands for geostationary. The projection is described in detail >in the "CGMS 03, LRIT/HRIT Global specification" document. >(see here also: http://remotesensing.org/geotiff/proj_list/geos.html ) > >My question is thus: how do we make a proposal for the addition of the >projection ? > >On a side note, it looks like "Vertical perspective" and "geos" are >mixed up in the current version of the conventions (the link to "geos" >is provided under "Vertical perspective"). The difference is that the >geos projection is related to scanning angles of the satellite, so that >the projection is done on a piece of a sphere, while the vertical >perspective is a kind of orthographic projection. > >Here comes a possible text for this projection: > > >Geostationary >- ------------- > >grid_mapping_name = geos > > >Map parameters: > > latitude_of_projection_origin > > longitude_of_projection_origin > > perspective_point_height > > false_easting > > false_northing > >Map coordinates: > > The x (abscissa) and y (ordinate) rectangular coordinates are >identified by the standard_name attribute value projection_x_coordinate >and projection_y_coordinate respectively. > >Notes: > > Notes on using the PROJ.4 software packages for computing the >mapping may be found at >http://www.remotesensing.org/geotiff/proj_list/geos.html . These notes >assume the point of observation is directly over the equator. >============================== > > >Thanks a lot ! >Best regards, >Martin >-----BEGIN PGP SIGNATURE----- >Version: GnuPG v2.0.14 (GNU/Linux) >Comment: Using GnuPG with Red Hat - http://enigmail.mozdev.org/ > >iQEcBAEBAgAGBQJOy5VwAAoJEBdvyODiyJI4uCYIAIBdFb7vgvg6ro4k/uWDm1VZ >JehlzqZl+CVBN0wFlVABgAe3UHKOS3Q1IEr9+JkcvFzxsMFSHfaCmj02IeqtV5cQ >yTbI+3KgHnKC9udXnbl84aMOmUZHvalBkM0+2Rc49pmNvd2xqC0FZDqclnVqM0Gf >8Rrq66txOh2tBK1rJO94EVq4p8JtbC78Dd9ayiHdUZwKz/DlxePR6YgYqcMyci9M >MtXV3kdvsgYzl8epzyrEoCyuSMdabOzmgUnztWadDUMidQtp6ygcHXcbLmSq8KMS >SGEmgyJIbCt4Krm+aKNU0bKpbsPrOmb6ZbnHCZb4DvVtxIcu0PzaV73366Maheg= >=KY33 >-----END PGP SIGNATURE----- > > ..............End of Message ...............................-->
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