[cf-satellite] Ang.: Making a proposal for the addition of the geos projection

• To: John Caron <caron@xxxxxxxxxxxxxxxx>, "cf-satellite@xxxxxxxxxxxxxxxx" <cf-satellite@xxxxxxxxxxxxxxxx>
• Subject: [cf-satellite] Ang.: Making a proposal for the addition of the geos projection
• From: Raspaud Martin <martin.raspaud@xxxxxxx>
• Date: Tue, 22 Nov 2011 22:39:32 +0000

Hi John,

This looks familiar indeed... The document cited there is the CGMS03, which 
describes the geos projection. However, I am not sure what scale_x and y are ?

Should we merge the two descriptions somehow for the proposal ?

Best regards,
Martin

----- Reply message -----
Från: "John Caron" <caron@xxxxxxxxxxxxxxxx>
Till: "cf-satellite@xxxxxxxxxxxxxxxx" <cf-satellite@xxxxxxxxxxxxxxxx>
Rubrik: [cf-satellite] Making a proposal for the addition of the geos projection
Datum: tis, nov 22, 2011 18:01



Hi Martin:

Im wondering what relationship this projection has (if any) with the meteosat 
projection:

http://www.unidata.ucar.edu/software/netcdf-java/reference/StandardCoordinateTransforms.html#MSG

John

On 11/22/2011 5:28 AM, Martin Raspaud wrote:

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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
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    • From: Martin Raspaud
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    • From: John Caron