Hi John,
As you know there are two basic "schools" of thought on how to represent
projected grids:
1. by naming the projection and giving its parameters (as is done in GIS)
2. by giving is coordinates explicitly (as is done in CF)
What you are proposing is a mechanism to harmonize the two approaches in CF
files. This is an excellent idea. Since the typical purpose of including
this redundant (but useful) projection information is to make it easier for
GIS applications to access CF datasets, it makes most sense to borrow the
GIS encoding standards as closely as possible. I presume that this is what
you have done in your example (??). So the question that I bounce back to
you is:
* Can you propose a particular GIS document (standard) for encoding
projection information and a general mapping from that document into CF
attributes?
I believe this is the question that we want to address, rather than the
particulars of the Lambert Conformal projection.
- steve
========================================================
John Caron wrote:
> I didnt easily find an example of using a projection coordinate systm in
> the CF docs, so i generated one.
> It would be great to get it included so i can just point people to that
> doc.
> Let me know if i did anything wrong.
>
> thanks!
>
> dimensions:
> y = 228;
> x = 306;
> time = 41;
>
> variables:
> int Lambert_Conformal;
> Lambert_Conformal:grid_mapping_name = "lambert_conformal_conic";
> Lambert_Conformal:standard_parallel = 25.0;
> Lambert_Conformal:longitude_of_central_meridian = 265.0;
> Lambert_Conformal:latitude_of_projection_origin = 25.0;
> double y(y);
> y:units = "km";
> y:long_name = "y coordinate of projection";
> y:standard_name = "projection_y_coordinate";
> double x(x);
> x:units = "km";
> x:long_name = "x coordinate of projection";
> x:standard_name = "projection_x_coordinate";
> double lat(y, x);
> lat:units = "degrees_north";
> lat:long_name = "latitude coordinate";
> lat:standard_name = "latitude";
> double lon(y, x);
> lon:units = "degrees_east";
> lon:long_name = "longitude coordinate";
> lon:standard_name = "longitude";
> int time(time);
> time:long_name = "forecast time";
> time:units = "hours since 2004-06-23T22:00:00Z";
> float Temperature(time, y, x);
> Temperature:units = "K";
> Temperature:long_name = "Temperature _at_ surface";
> Temperature:missing_value = 9999.0;
> Temperature:coordinates = "lat lon";
> Temperature:grid_mapping = "Lambert_Conformal";
>
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--
Steve Hankin, NOAA/PMEL -- Steven.C.Hankin at noaa.gov
7600 Sand Point Way NE, Seattle, WA 98115-0070
ph. (206) 526-6080, FAX (206) 526-6744
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