| Re: Map_Proj_Inverse Bug? [message #64425] |
Mon, 29 December 2008 12:57 |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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David Fanning writes:
> Any explanation for why my longitude values are depending on
> the latitude values I use in Map_Proj_Init? Do you think this
> could be a bug?
The results seem to be more what I expect if I use a Mercator
project, rather than a Transverse Mercator:
IDL> mapStruct = Map_Proj_Init(105) ; Mercator
IDL> Print, mapStruct.uv_box[[0,2]], mapStruct.uv_box[[1,3]]
-20037726. 20037726.
-88943645. 88943645.
IDL> Print, Map_Proj_Inverse(mapStruct.uv_box[[0,2]], $
IDL> mapStruct.uv_box[[1,3]], $
IDL> MAP_STRUCTURE=mapStruct)
-180.00000 -89.999900
180.00000 89.999900
IDL> Print, Map_Proj_Inverse(mapStruct.uv_box[[0,2]], $
IDL> [0,0], $
IDL> MAP_STRUCTURE=mapStruct)
-180.00000 0.00000000
180.00000 0.00000000
IDL> Print, Map_Proj_Inverse([0,0], $
IDL> mapStruct.uv_box[[1,3]], $
IDL> MAP_STRUCTURE=mapStruct)
0.00000000 -89.999900
0.00000000 89.999900
Verses this:
IDL> mapStruct = Map_Proj_Init(109) ; Transverse Mercator
IDL> Print, mapStruct.uv_box[[0,2]], mapStruct.uv_box[[1,3]]
-6411813.8 6411813.8
-9997887.3 9997887.3
IDL> Print, Map_Proj_Inverse(mapStruct.uv_box[[0,2]], $
IDL> mapStruct.uv_box[[1,3]], $
IDL> MAP_STRUCTURE=mapStruct)
0.00000000 -90.000000
0.00000000 90.000000
IDL> Print, Map_Proj_Inverse(mapStruct.uv_box[[0,2]], $
IDL> [0,0], $
IDL> MAP_STRUCTURE=mapStruct)
-50.317650 0.00000000
50.317650 0.00000000
IDL> Print, Map_Proj_Inverse([0,0], $
IDL> mapStruct.uv_box[[1,3]], $
IDL> MAP_STRUCTURE=mapStruct)
0.00000000 -90.000000
0.00000000 90.000000
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")
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