changing cell resolution

[Malcolm Williamson]

On Tue, 27 Jun 1995, GREEN WILLIAM G wrote:

> 
> Last week I asked about increasing the 25 cell limit in r.neighbors because
> I needed to look at an area beyond the 25 cells (i.e., 10,000 ft.).
> I found that rather than changing the source code (which I am technically
> incapable of doing), I could simply increase the resolution of each cell
> from 25 meters to 200 meters.  The question I have is when you increase a 
> cell's resolution, what value does it use.  For example, does it use the 
> existing value of the center cell or does it average all of the cells that
> it is incorporating. 
> 
Hi, Bill
GRASS uses "nearest neighbor" resampling. Thus, if you were resampling from 
5 meter to 25 meter resolution, resulting in an odd number of "old" cells 
fitting in your "new" cells, the value of the center "old" cell would be 
assigned to the "new" cell. If you were resampling from 5 meter to 50 meter
resolution, resulting in an even number of "old" cells per "new" cell, the 
value in the UPPER-LEFT cell of the CENTER FOUR "old" cells would become the 
value assigned to the "new" cell.

Hope that makes sense to you! Regards,
---
Malcolm D. Williamson - GIS Specialist           E-mail: malcolm at cast.uark.edu
Center for Advanced Spatial Technologies      Telephone: (501) 575-6159
Ozark Rm. 12                                        Fax: (501) 575-5218 
University of Arkansas              
Fayetteville, AR 72701