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Re: Map_Image and interpolation [message #18239 is a reply to message #18231]

Wed, 08 December 1999 00:00

davidf
Messages: 2866
Registered: September 1996

Senior Member

Ben Tupper (tupper@seadas.bigelow.org) writes:

> I have a set of ship positions (Lon/Lat in WGS 84 map datum). I also
> have a bathymetric grid which I have warped into a tranverse mercator
> projection (Datum = WGS 84). The ship locations plot correctly on the
> warped image. Now I would like to interpolate values off of the warped
> image between consecutive ship locations.

Uh, why?! Surely the ships (and the bathymetric gird)
are in "real" space (as opposed to, say, "map" space)
and the interpolation should be done there. Once you
have the interpolated data, you just put it on the
map coordinate system using PLOTS, or whatever you do.
This is the beauty of the Map_Set command: it sets
up the mapping between your real coordinate system
and the map coordinate system.

> So how do I go from Ship Lon/Lat to WarpedGrid[X,Y]?

Make your calculations in Lon/Lat space and then
just *place* them on the Map, using the !Map system
variable to handle any transformations for you.

Cheers,

David

P.S. I have a sneaking suspicion I have completely
missed the point here. If so, I apologize profusely. :-)

--
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

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[Message index]

		Re: Map_Image and interpolation By: Liam Gumley on Thu, 09 December 1999 00:00
		Re: Map_Image and interpolation By: davidf on Thu, 09 December 1999 00:00
		Re: Map_Image and interpolation By: Ben Tupper on Thu, 09 December 1999 00:00
		Re: Map_Image and interpolation By: davidf on Wed, 08 December 1999 00:00
		Re: Map_Image and interpolation By: Ben Tupper on Wed, 08 December 1999 00:00
		Re: Map_Image and interpolation By: davidf on Wed, 08 December 1999 00:00

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