- manual page
The speed of r.sun is much higher ifis used first and the resulting maps are given as input to r.sun. Background: the horizon needs to be computed only one time before, not in every step within r.sun. See the example at the end of the help page.
Create an artificial surface containing a Gaussian mound:
out=gauss method=gaussian kurtosis=1
The following three images demonstrate the effects of using different time step parameters.
r.sun -s elevin="gauss" glob_rad="rad.global.30minT" day=180 step=0.5
r.sun -s elevin="gauss" glob_rad="rad.global.15minT" day=180 step=0.25
r.sun -s elevin="gauss" glob_rad="rad.global.03minT" day=180 step=0.05
The 3 minute time step takes roughly ten times as long to run as the 30 minute timestep.