r.slope.aspect (& now s.surf.tps)

[Craig Neidig]

> From grass-lists-owner at max.cecer.army.mil Tue Dec 29 13:04:05 1992
> From: jianp at ocean.rutgers.edu (Jianping Xu)
> Sender: lists-owner at max.cecer.army.mil
> Reply-To: grassu-list at max.cecer.army.mil
> Subject: Re:  180 degree offset of r.slope.aspect (& now s.surf.tps)
> Content-Length: 621
> X-Lines: 16
> 
> I used the r.mapcalc to obtain a "true azimuth" map which starts 
> with due N and from ZERO, and goes clockwise:
> 	r.mapcalc new_aspect = '(24 + 7 - old_aspect)%24'
> 
> If you would like the N to be value ONE, you may use:
> 	r.mapcalc new_aspect = '(24 + 8 - old_aspect)%24'
> 
> The only problem is no data (0) and flat (25) will also be transferred 
> to some "real" aspect values. However it's effect will be very minor
> since an aspect value is only significant when the slope is not zero.
> 
> Jianping Xu
> Rutgers University
> Cook College Remote Sensing Center
> New Brunswick, NJ 08903-0231
> (908)932-9631 email jianp at ocean.rutgers.edu
> 
Thanks to Mr. Jianping for his fix, but ...

Pardon me this is bogus --

a user should not have to "jump through hoops"
to get a program to do something it should do 
correctly in the first place.

Craig Neidig
USACERL
Technical Assistance Center