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Re: How to extract pixel values from a GeoTIFF using an Esri Shapefile [message #74091 is a reply to message #74079]

Thu, 23 December 2010 13:34

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

Paul Magdon writes:

> ;Convert SHP to ROI object
> myroi = OBJ_NEW( 'IDLanROI',( *ent.vertices)[0,*] ,(*ent.vertices)
> [1,*] )
>
> ;Apply ComputMask method
> maskResult = myroi -> ComputeMask(DIMENSIONS = [s[0],
> s[1]],MASK_RULE=2)
>
> ; Here starts the problem; I have a 5000x5000 raster (img) and the
> image coordinate system start with [0,0] but the myroi coordinates are
> much higher (eg 227984.00 ; 991472.00) Thus everything is masked.
> ;There is a keyword LOCATION for ComputeMask but I am not sure how to
> use it and where to get the right values for it

I have to admit I have never done this before. (Although
I would like to try if you could make the image and
shape file available to me.) But, it seems to me
that when you create the ROI, you will have to give
the ROI the range of the image to make this work.

mapCoord -> GetProperty, XRANGE=xr, YRANGE=yr
myroi = OBJ_NEW( 'IDLanROI',( *ent.vertices)[0,*] ,$
(*ent.vertices)[1,*], ROI_XRANGE=xr, $
ROI_YRANGE=yr )

That way, the ROI and the image are mapped to the same
coordinate system.

I'm curious to know if that works. :-)

Cheers,

David

P.S. The next book I am thinking of writing is a small
book about map projections in IDL. The more examples I
have like this, the better. I have to write this book
before I forget everything I've learned in the past four
years. :-)

--
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: How to extract pixel values from a GeoTIFF using an Esri Shapefile By: David Fanning on Sat, 01 January 2011 10:32
		Re: How to extract pixel values from a GeoTIFF using an Esri Shapefile By: Paul Magdon on Sat, 01 January 2011 10:24
		Re: How to extract pixel values from a GeoTIFF using an Esri Shapefile By: David Fanning on Sat, 25 December 2010 07:34
		Re: How to extract pixel values from a GeoTIFF using an Esri Shapefile By: Paul Magdon on Sat, 25 December 2010 05:32
		Re: How to extract pixel values from a GeoTIFF using an Esri Shapefile By: David Fanning on Thu, 23 December 2010 13:34
		Re: How to extract pixel values from a GeoTIFF using an Esri Shapefile By: Paul Magdon on Mon, 03 January 2011 04:30

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