| Map_Image and interpolation [message #18243] |
Wed, 08 December 1999 00:00 |
Ben Tupper
Messages: 186
Registered: August 1999
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Senior Member |
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Hello,
<p>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.
<p>I need to interpolate between two locations using Z = INTERPOLATE(WarpedGrid,
X, Y) where X and Y are vectors of arbitrary length in WarpedGrid coordinates.
<p>I tried the some thing terribly clever, like this:
<p>Sz = Size(WarpedGrid, /Dimensions)
<p>NormalXYZ = Convert_Coord(ShipLon, ShipLat,/Data,/To_Normal)
<br>X = NormalXYZ[0,*]*(SZ[0]-1)
<br>Y = NormalXYZ[1,*]*(Sz[1]-1)
<p>Good try, but the X, Y values are not located correctly on the WarpedGrid
and the ship seems to be aground. Oopsie!
<p>So how do I go from Ship Lon/Lat to WarpedGrid[X,Y]?
<pre>Thanks,</pre>
<pre>Ben</pre>
<pre>--
Ben Tupper
Bigelow Laboratory for Ocean Science
tupper@seadas.bigelow.org
Pemaquid River Company
pemaquidriver@tidewater.net</pre>
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