Algorithm for slope angle calculation -2nd try

[Juergen]

Maybe it's a bad idea to post a question on a friday afternoon. Perhaps
I have better luck on a tuesday ;-)

Juergen

+++++++++++++++++++++++++ 

Hello!

The documentation to r.mapcalc "r.mapcalc - An algebra for GIS and Image
Processing" from Michael Shapiro and Jim Westervelt explains on page 10
an alternative algorithm for slope angle calculating, which has been
developed by Frank (1988) in "mapping dominant vegetation communities in
the Colorado Rocky Mountain Front Range with Landsat Thematic Mapper and
Digital Terrain Data", published in "Photogrammetric Engineering and
Remote Sensing", Vol. 54, 12, p. 1727-1734

If I compare the matrix explained in the text 

0 0 0 0 0
0 0 0 0 0
1 8 0 -1 -8
0 0 0 0 0
0 0 0 0 0

with the r.mapcalc-example, that will look like

0 0 0 0 0
0 0 0 0 0
1 8 0 -8 -1
0 0 0 0 0
0 0 0 0 0

I see a difference (you too?)

Does someone of you know, which of the matrixes is the right one?
Who has this volume of "Photogrammetric Engineering and Remote Sensing"
and can take a look in it?

Many thanks in advance

Juergen Rogozia