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Re: Retrieve pixel values from GeoTIFF [message #73785 is a reply to message #73784]

Sat, 27 November 2010 12:59

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

David Fanning writes:

>
> mankoff writes:
>
>> David: I've also tried using your GeoCoord object, and can display the
>> graphic and coastlines just fine, but again, am stuck at the step of
>> "convert (lon,lat)=(-100,-75) to (x,y) for indexing into the original
>> TIF".
>
> mapCoord = GeoCoord('mygeotiff_file.tif')
> mapStruct = mapCoord -> GetMapStructure()
> xy = Map_Proj_Forward(lon,lat, Map_Structure=mapStruct)
> x = xy[0]
> y = xy[1]

Oh, wait! You said you want to index into the original
image. (My son is bugging me about bying a car today,
so I'm distracted. :-)

In addition to the above, I would do this.

mapCoord -> GetProperty, XRANGE=xr, YRANGE=xy
s = Size(image, /Dimensions)
xvec = Scale_Vector(Findgen(s[0]), xr[0, xr[1])
xindex = Value_Locate(xvec, x)
yvec = Scale_Vector(Findgen(s[1]), yr[0], yr[1])
yindex = Value_Locate(yvec, y)

Then,

Print, image[xindex, yindex]

Cheers,

David

--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")

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[Message index]

		Re: Retrieve pixel values from GeoTIFF By: David Fanning on Sat, 27 November 2010 13:03
		Re: Retrieve pixel values from GeoTIFF By: David Fanning on Sat, 27 November 2010 12:59
		Re: Retrieve pixel values from GeoTIFF By: David Fanning on Sat, 27 November 2010 12:52
		Re: Retrieve pixel values from GeoTIFF By: mankoff on Sat, 27 November 2010 12:45
		Re: Retrieve pixel values from GeoTIFF By: David Fanning on Sat, 27 November 2010 12:13
		Re: Retrieve pixel values from GeoTIFF By: penteado on Sat, 27 November 2010 12:06

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