| Re: Resolution returned from MAP_PROJ_IMAGE? [message #64016] |
Mon, 24 November 2008 09:40 |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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bryan.s.hong@gmail.com writes:
> I'm using NLDAS (North America Land Data Assimilation System) data
> which has 0.125 degree resolution with 464 X 224 grid boxes, and I'm
> trying to project this data to the Albers map projection using the
> code below. The LIMIT key used in the MAP_PROJ_IMAGE indicates the
> total area coverage of NLDAS. Using this code, the result returns with
> 464 X 224 grid boxes which are the exact same size as the original
> data input. How can I know the spatial resolution of the result. I
> believe the result should have a spaptial resolution in meters, right?
> Is there any way to give a specific resolution when the original data
> are being wapred?
>
> sMap = MAP_PROJ_INIT(103, SEMIMAJOR_AXIS=6378137.0,
> SEMIMINOR_AXIS=6356752.31414,$
> FALSE_EASTING=0., FALSE_NORTHING=0,
> STANDARD_PAR1=29.5,$
> STANDARD_PAR2=45.5, CENTER_LATITUDE=23.,
> CENTER_LONGITUDE=-96.)
> Result = MAP_PROJ_IMAGE(Image, [-125.,25.,-67.,53.],
> Map_structure=sMap, missing=0)
I presume the results have the same units as your map
projection, which appear to be in meters. The resolution
is the extent (in meters) divided by the number of pixels
in the result. You can increase or decrease the number
of pixels in the result by using the DIMENSION keyword
to MAP_PROJ_IMAGE.
Cheers,
David
--
David Fanning, Ph.D.
Coyote's Guide to IDL Programming (www.dfanning.com)
Sepore ma de ni thui. ("Perhaps thou speakest truth.")
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