| Re: Map image with a sparse array [message #18650] |
Mon, 24 January 2000 00:00  |
Liam E. Gumley
Messages: 378
Registered: January 2000
|
Senior Member |
|
|
whdaffer@my-deja.com wrote:
> Can anyone see what I'm doing wrong?
>
> When I tv the mapped image and compare it to the unmapped image, it's
> clear that the mapped image has included some 'bad' data in the
> calculations of points within the grid.
>
> To be fair, this possibility is not explicitly excluded in the help
> file. If I'm reading it correctly, all it says is that output grid
> values which are within the valid mapping limits but which exceed input
> maxima will be set to the 'bad data' value, not that the input 'bad
> data' value will be excluded from caluclations.
>
> The effect is not large, but it isn't small either. The person I'm
> doing the work for noticed it right off.
>
> By the way, I did try your method first, (bytscl, then map_image) and
> got similar results, but thought that I should make the bytscl be the
> last step, since it reduces the 'color' resolution from 360 values to
> about 200. I'll go back and try your method again. Perhaps there's some
> magic that I'm not seeing.
William,
I pulled that section of code from a procedure that projects a 720x360
global grid with missing data onto various map projections. I cannot see any
hint that the missing data corrupted the resulting image:
ftp://origin.ssec.wisc.edu/pub/gumley/IDL/grid_project002.gi f
Cheers,
Liam.
--
Liam E. Gumley
Space Science and Engineering Center, University of Wisconsin-Madison
http://cimss.ssec.wisc.edu/~gumley
|
|
|
|
comp.lang.idl-pvwave archive
Members
Search
Help
Login
Home
