Difference between revisions of "GRASS Raster Mask"

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'''Q:''':  I do not have the concept of mask. Please anybody help me in understanding mask. What is this?
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'''A:''' A mask allows you to block arbitrary areas of all rasters processed while the mask is set. That is, for cells where the mask is set, those cells will be treated as if they were NULL. It was more important when GRASS didn't have a true concept of NULL value (GRASS 4.x), however, masks still can be useful even in GRASS 5.x
 
  
Masking can be even used in ps.map script, so a raster mask can applied to vector features that one wants to be masked, it is done by the masked y|n switch.
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'''Question'''
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I don't understand the concept of the ''MASK''. What is it?
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'''Answer'''
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A MASK allows you to block arbitrary areas of all raster maps processed while the MASK is set. That is, those cells for which the MASK is set, will be treated as if they were NULL. Originally, it was important when GRASS didn't have a true concept for the ''NULL'' value (GRASS 4.x). It is, however, still very useful in all GRASS versions (5.x, 6.x and 7.x). MASKing can be even used inside a <code>ps.map</code> script. This way, a raster MASK can be applied to vector features that need to be masked. This is achievable by using the masked <code>y|n</code> switch.
  
 
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Latest revision as of 02:57, 5 February 2013

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Question

I don't understand the concept of the MASK. What is it?

Answer

A MASK allows you to block arbitrary areas of all raster maps processed while the MASK is set. That is, those cells for which the MASK is set, will be treated as if they were NULL. Originally, it was important when GRASS didn't have a true concept for the NULL value (GRASS 4.x). It is, however, still very useful in all GRASS versions (5.x, 6.x and 7.x). MASKing can be even used inside a ps.map script. This way, a raster MASK can be applied to vector features that need to be masked. This is achievable by using the masked y|n switch.