[GRASS-user] r.param.scale curvatures: are really OK

[Jasiewicz Jarosław]

Hi
while I modified r.param.scale for my purposes I noticed that some 
formulas for curvatures differs from that I know:


for example:

plan curvature: is

(2.0 * (b * d * d + a * e * e - c * d * e) /
             pow(e * e + d * d, 1.5));

probably shall be:

( (b * d * d + a * e * e - 2.0 *(c * d * e)) /
             pow(e * e + d * d, 1.5));


profile curvature: is

         return (-2.0 * (a * d * d + b * e * e + c * e * d) /
             ((e * e + d * d) * pow(1.0 + d * d + e * e, 1.5)));

probably shall be:

         return (- (a * d * d + b * e * e + 2.0* (c * e * d)) /
             ((e * e + d * d) * pow(1.0 + d * d + e * e, 1.5)));

Of course threre could be reasons why little different formulas are used 
but I do not see any.

This formulas is in grass 6.4, 6.5 and 7.0 and I assume in older version 
too.

regards
Jarek