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Last Post 10 Sep 2007 04:19 AM by  anon
How to rasterize point data without interpolation?
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anon



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10 Sep 2007 04:19 AM
    I have an ASCII file with several columns, defining X and Y coordinates in the geographic projection and estimated quantities. I have defined a ROI on an remote sensed image, dumped it to an ASCII file, and processed it with my program, estimating some ground quantities of my interest and saving results to similar file. First two columns, containing coordinates, remain unchanged. Now I want ENVI to produce a map of these quantities. The only way I have discovered is Vector -> Rasterize point data. However, this procedure is designed for rasterizing unevenly spaced points and producing a "smooth" image.with filling empty points with interpolated values. This doesn't satisfy me. I want to produce a map with the same dimensions as the original one has, having estimated values written exactly in the pixels, from which the measured values were taken, and 0s in the pixels, which originally were outside the ROI.

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    10 Sep 2007 04:19 AM
    If I understand your problem correctly, you have an image and an ROI and you want to produce a new image such that every pixel inside the ROI has the original image's value, and every pixel not in the ROI is 0. If that's the case, here's what I would do: 1) Take your original image that has the ROI defined, and create a mask for that image such that every point in the ROI has a value of 1 and every pixel not in the ROI is zero. Do this with Basic Tools -> Masking -> Build Mask. In the dialog box that comes up, select import ROIS... from the Options menu. 2) Go to Basic Tools -> Masking -> Apply mask, select the input file and the mask band, and that should give you an image where each point outside the ROI is 0, and each point inside the ROI is the original value from the input file. Note that you could also do this step with band math (b1*b2, where b1 = your input file, and b2=mask). Hope that helps, Jeff
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