Re: Newbie needs help...

[davidf(at)dfanning.com (David Fanning)]

Bruce Bowler (bbowler@bigelow.org) writes:
 
> I'm willing to try this "thinking outside the box" thing for a while,
> but I can't see the box.

There is no box. (But see more on spiritual development, below.)

> Now that I have my image mapped on to a lat/lon grid (see, I'm learning
> already :-), how to I access the data by lat/lon?

You are going to love this! :-)

You have set up the map coordinate space with Map_Set.
You have placed your image on the map with Map_Image
(or something similar). You put your map grid and
continental boundary on your map with Map_Grid
and Map_Continents.

Now, you get lat/lon value from the user by just
having them click on the map! Too easy!

   Cursor, lon, lat, /Data

Now, what you do next depends on you. If you
have an image data set in which each pixel
has an associated lat/lon coordinate, you can
go pull out the closest pixel value from that
data set. 

If you don't have such a data set, you might
have to get the value from the warped image.
That value, of course, was created by smushing
(technical term) several real values together
in the warping process. It may not be what you
want. (How this is done is fairly complicated.
I'd explain it, but I'm pretty sure it's not
what you want to do anyway.)

> > if you persist I can recommend "getting used
> > to disappointment" as the appropriate spiritual practice.
> > 
> > Cheers,
> 
> Those two sentiments don't seem to go together :-(

Oh, I don't know. I find it an easier spiritual 
practice than "do the dishes, again", which is what
I usually do in my search for enlightenment. :-)

Cheers,

David
-- 
David Fanning, Ph.D.
Fanning Software Consulting
Phone: 970-221-0438 E-Mail: davidf@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Toll-Free IDL Book Orders: 1-888-461-0155