Re: overlying data on an image

[deja_jlin(at)my-deja.com (Johnny Lin)]

hi Jairo,


Jairo Santana <santana@icesat2.gsfc.nasa.gov> wrote in message:
> I have a grid of elevation heights in geo coordinates. Also I have
> points:
> lats, lons, heights. I need to plot the lats, lons, and heights on top
> of the grided image. How can I do that? Do I need to grid the data
> points (lat,lon,h) first? any suggestion/code will help.
> 
> Thanks,
> Jairo.
>
do you mean you have a grid of heights and an image of the same
location, and you want to superimpose contours of the heights onto
the image?  if so...

David Fanning answers just that question in his excellent book
_IDL Programming Techniques_, which i highly recommend.  i've the
feb. 1999 edition, and it's on p. 102 in that version (in a section
entitled "combining simple graphical displays").  the url to his
website:

   http://www.dfanning.com/

anyhow, the summary of the method is use TVIMAGE to write the image,
and set the Keep_Aspect_Ratio keyword to 1 to output the position
of the image via the Position keyword.  then pass that value into
your call to CONTOUR via its Position keyword, w/ Noerase set.

re gridding, as long as your data is in a grid (even if it's not a
regular grid), then CONTOUR will work fine.  if not, then you'll
have to grid it using TRIANGULATE or SPH_SCAT (for spherical triangles).

best,
-Johnny


-------------------------------------------
Johnny Lin
CIRES, University of Colorado
Work Phone:  (303) 735-1636
Web:  http://cires.colorado.edu/~johnny/
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