LASground _detailed params

[jan.zachar]

Hello everybody

is there any short tutorial how to change/add detailed. params in lasground function like spike, bulge and step. In txt files they are mentioned but I cannot figure out how to add resp change them I dont see them neither in GUI nor in comand line option.

Thanks a lot

[Martin Isenburg]

Hello Jan,

Initially lasground creates a ground estimate by using the lowest point in each cell of a coarse grid whose cell size is determined by the step parameter. The '-wilderness' is just a short-hand for a step of 3 meter. Just like '-town' is a short-hand for a step of 10 meter. Also some of the other parameters change as you can see above. 

http://rapidlasso.com/lasground

http://lastools.org/download/lasground_README.txt

http://lastools.org/download/lasground_new_README.txt

The bulge parameter defines how "high" coarse triangles of the coarse TIN are allowed to "bulge up" when deciding about whether to insert the currently considered last return into the slowly refining ground TIN or not. The lower you set it the less the TIN is bulging up and the more features (little hills) are potentially chopped off. Setting it to zero or asking for 'no_bulge' can be quite aggressive - especially for a larger '-step'.

The spike parameter is used between refinement passes. After each we refinement we check in the current TIN if any of the inserted points forms too much of an up or a down "spike" with its immediate one-triangle-ring of other points. If the observed spike exceeds the specified spike (vertically) it is removed. Hence, a larger '-spike' value is useful if you expect your ground TIN to have great variation or if you want some features in the ground (e.g. an archaeological DTM).

Finally there is also '-stddev'. That is a special option designed to, for example, get cleaner roads in steep mountains and not "chop off" so much of the road near the two steep sides. In some cases this may have undesirable side-effects so try to set it to zero or simply add '-no_stddev' to the command line.

Regards,

Martin @rapidlasso

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