[GRASS-user] [LAStools] lasground options -fine and -extra_fine: is the only difference processing speed?

[Martin Isenburg]

Hello Adam,

the '-fine', '-extra_fine', and '-ultra_fine' option specifies how much work the algorithm should invest to find the *initial* ground estimate that will get refined subsequently. As a rule of thumb you need a finer ground estimate the steeper your terrain. The option essentially defined how fine of a subgrid should be used to look for probable ground returns between the chosen step size. Each finer option quadruples the granularity of this subgrid (whose unrefined size is detmined by the step size). For very steep terrains extra fine is recommended but also for flat areas with subtle bumps in the ground the ultra fine setting can help to get better detail. For computing tree canopies, for example, in flat terrain the default granularity should be fine enough.

Cheers,

Martin       

On Jun 17, 2013, at 20:55, Adam Pryor <adam at extro.com.au> wrote:
> In lasground do the _fine and extra_fine options simply search a larger proportion of the points to find ground points (requiring longer processing time), or does it use a different method too?
> 
> i.e. Is the only downside longer processing or could there be another benefit for going with a coarser search?
> 
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