| problems converting to Cylindrical (longitude-latitude) [message #42417] |
Mon, 07 February 2005 07:06  |
Jeff DLB
Messages: 2
Registered: February 2005
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Junior Member |
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I'm having trouble converting images to Cylindrical (longitude-
latitude) coordinates. My input data are in Albers Equal-Area
and cover the western US. When I convert to lon-lat coordinates
I get output images and bounds that are clearly wrong. I must be
misusing MAP_PROJ_INIT and MAP_PROJ_IMAGE, but am not sure how.
Any suggestions would be welcome.
Here's what I have tried:
; Data are in Albers Equal-Area; output is to be Cylindrical.
; Albers projection parameters
spar1 = 20
spar2 = 60
clon = -103
clat = 45
; Corners of images (in meters) as stated in metadata.
xmin = -1567000.0
xmax = 277000.0
ymin = -1760000.0
ymax = 694000.0
xyrange = [xmin, ymin, xmax, ymax]
; Compute !MAP structure for each projection.
mapIn = map_proj_init('Albers Equal Area', datum='Clarke 1866', $
standard_par1=spar1, standard_par2=spar2, $
center_longitude=clon, center_latitude=clat)
mapOut = map_proj_init('Cylindrical', datum='Sphere')
; Input image is imgIn. Compute output image.
imgOut = map_proj_image(imgIn, xyrange, image_structure=mapIn, $
map_structure=mapOut, uvrange=latLonRange)
print, lonLatRange
-14014183. 3207349.0 -10991525. 5658023.0
The resulting UVRANGE values are clearly not within +/-360 E-W, +/-180
N-S.
The image metadata states the lon-lat bounds are
lower left lat 28.8444, lon -119.7528
upper left lat 49.2565, lon -126.0326
upper right lat 50.8321, lon -98.8492
lower right lat 30.0061, lon -100.0084
Thanks for any suggestions,
Jeff DLB
Reprojection newbie
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