[GRASS5] r.mapcalc: Neighborhood cell index

[Roger Bivand]

On Tue, 18 Feb 2003, Markus Neteler wrote:

> Dear developers,
> 
> a question related to r.mapcalc's scheme of neighborhood cell index:
> 
> In Larson, Shapiro, Tweddale, 1991, "Performing Map Calculations on GRASS
> Data: r.mapcalc Programa Tutorial", 3.5. Neighborhood modifiers, p.8.
> http://grass.itc.it/gdp/raster/mapcalc.pdf
> 
> is written:
> "format is map[r,c],..."
> "map[1,2] refers to one row below and two columns to the right..."
> 
> That means:
>  map[y,x] with x positive to "East" and y positive to "South".
> 
> For curiousity: Is there a particular reason to have the orientation
> pointing positive to South?
> 
Because rows start at 0 at the northern edge? Then the n/s offsets would 
work without reversal?

Roger

-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Breiviksveien 40, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 93 93
e-mail: Roger.Bivand at nhh.no