6/2002:

GENERAL

for this version of r.answers, the user must set NULL for values with no
data (not 0's) for all the maps.

SLOPE MAP

To generate the slope map needed by answers  the creators of r.answers
advised to use r.slope. But this program can generate some NULL values; 
so it recommended to use r.slope.aspect, and r.mapcalc to generate the
slope map as needed by answers:

 mapcalc>slope.answers.format=10*slope.from.r.slope.aspect

The map obtained in this way will be a floating values one. But I've checked
that it's no problem for r.answers.

ASPECT MAP

Besides r.direct, it is also possible to generate an aspect map with
r.slope.aspect, and use r.reclass, in the way:

0 thru 21 = 360 east
22 thru 66 = 45 east-north
67 thru 111 = 90 north
112 thru 156 = 135 north-west
157 thru 201 = 180 west
202 thru 246 = 225 west-south
247 thru 291 = 270 south
292 thru 336 = 315 south-east
337 thru 360 = 360 east
end

and the aspect map, as needed by r.answers using r.mapcalc with:
 mapcalc>aspect.answers=aspect.reclassed.from.r.slope.aspect

After this, we must use, anyway, d.rast.edit as mentioned in the 'answers
exercise'. The maps so obtained appear slightly different from those
obtained through r.direct.

---------------------
Javier Garcia
andresjavier.garcia@wanadoo.es
CEBAS-CSIC



3/2001:
r.fill.dir is located now in src/raster/r.fill.dir