Raster Calculator Blurring Image Results

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07-28-2014 07:35 AM
TommiTiidus
New Contributor

I am trying to run a NDVI analysis using raster calculator on Arg Map 10.2.1 and the results create blurry or bleeding image, almost as if the map has been dipped in water. I am using the default environment settings in the raster calculator. Both the bands being entered are very clear and have high resolution, I can see individual plants and rows in a farm field, but when I run the NDVI the resolution seems to get blurred. It almost seems like the raster calculator seems to automatically create a Guassian Blur for the image. Has anyone else encountered this and know of ways to overcome this blurring? 

Also I have also noticed that when running a raster calculator, the blurring only seems to occur when subtracting or dividing image bands, but not adding or multiplying, is there a reason for this?

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2 Replies
curtvprice
MVP Esteemed Contributor

Normally the default processing is the maximum of the two inputs.  You can see the output cell size in the layer properties (Source tab).

Another default is when you display a floating raster the display will be continuous, not nearest neighbor I can see how this may look like the resolution is "blurring" especially if you zoom in where the cells (would be) visible -- you can change the default by looking at the raster layer properties Display tab.

RustyRex
Occasional Contributor

I have seen blurring effects when the two rasters are not directly aligned or registered to each other.  You can overlay the two and identify to check the math of the calculation on  a few pixels. It's just a thought of something to look at along with Price's solution.

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