[GRASS-user] r.horizon distance units

[Nikos Alexandris]

On 11.08.2014 22:10, Tyler Smith wrote:

> Hello,

Hi Tyler,

> I'm having some trouble with r.horizon. I've got a very big DEM, and 
> I
> keep running out of memory. After some experiments, I think the 
> options
> bufferzone and maxdistance may be part of the problem. It isn't 
> listed
> in the help file what the units for these are.
>
> I'm preparing maps for use in r.sun, and the example in the r.horizon
> help page suggests I use bufferzone=200 and maxdistance=2000. Does 
> this
> mean meters? units from the map projection (which are degrees)? 
> Omitting
> these parameters I can complete an analysis in a minute or so, when
> including them produces a crash sometime after the process consumes 
> all
> my RAM and swap memory.

In all 6.x series as well as in GRASS ver. 7.0, the manual for 
r.horizon notes:

--%<---
At the moment the elevation and maximum distance must be measured in 
meters, even if you use geographical coordinates (longitude/latitude). 
If your projection is based on distance (easting and northing), these 
too must be in meters. The buffer parameters must be in the same units 
as the raster coordinates.
--->%--

Hope this helps further,
Nikos