ENVIPixelScaleResampleRasterTask - NV5 Geospatial

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Last Post 22 Oct 2021 06:28 AM by MariM

ENVIPixelScaleResampleRasterTask

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Marcos Montes

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Posts:33

21 Oct 2021 01:35 PM
I'm running ENVI 5.5.3 (with IDL 8.7.3). I don't think it matters, but I'm on a MacBook Pro running MacOSX 10.14.6. (I've checked an IDL 8.8/ENVI 5.6 that we have and it appears identical.) I've noticed that through the GUI, using Resize Data, when reducing the number of pixels (i.e., making them cover larger physical space on the ground), there is an option that allows pixel aggregation. However, in what seems to be the most closely related task (ENVIPixelScaleResampleRasterTask), the RESAMPLING keyword does not seem to take anything akin to "pixel aggregation". Am I missing something? Is there an ENVI task or procedure that does this already? A different task than the one above? Are the GUI tasks truly built differently than the available API? Thanks for any thoughts on this, -Marcos

MariM

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Posts:2396
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22 Oct 2021 06:28 AM
The pixel aggregate method was no included implemented in the newer tasks. We still offer the standard three methods when resampling in ENVI now – nearest neighbor, bilinear and cubic convolution. Nearest neighbor only uses a single pixel value (the nearest) one for the output pixel. Bilinear uses the combination of the closest 2 x 2 pixels and cubic convolution uses the closest 4 x 4. Technically, pixel aggregate would use as many pixels as necessary, depending on your resampling size, so if you were making your output 5x smaller than your input, PA would use the closest 5 x 5 pixels to produce the output pixel. So really, unless you are resampling down by factors greater than 4x, there won’t be any difference than using cubic convolution.

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