Fusion catalog-like LAStools feature

[Mauro Assis]

Hi,

In Fusion there´s a catalog.exe utility that shows the return density of a LiDAR file by creating an image of this file and setting colors corresponding to the return points density per area.

Is there a similar feature in LAStools? I´m asking for because it doesn´t provides me exactly what I need.

Tks,

Mauro

[Grzegorz Krok]

Hi Mauro,

You can use lasgrid with -counter switch.

lasgrid -i input.las -o output.tif -step 5 -counter

[Martin Isenburg]

Hello,

there are two options in 'lasgrid' to create counter rasters.

http://rapidlass.com/lasgrid

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

Either you can - as suggested - use the '-counter' switch which by default is only a one byte counter that can count from 0 to 255. If you expect more points in your area use '-counter_16bit' that can count from 0 to 65535'. That is usually enough unless you have a large step size and very dense LiDAR in which case you should use '-counter_32bit'. This just produces a counter for the number of returns falling into each 5 by 5 area (e.g. 25 square meters) assuming you used '-step 5'. For the visualization as a false color you need to do the math yourself. If blue is to be mapped to 5 point per square meters or less and red is supposed to be 10 points per square or more you need to multiply the values by 25 when you '-set_min_max 5*25 10*25' the color ramp for the '-false' coloring from blue to red.

lasgrid -in lidar.laz ^

            -last_only ^

            -step 5 -counter_16bit ^

            -false -set_min_max 125 250 ^

            -o density_5_10.png

However, to directly get area-normalized counts it may be more convenient to use the '-point_density' switch. Or the corresponding '-point_density_16bit' or  '-point_density_32bit' options. Here the number is already normalized by the area so you can simply '-set_min_max 5 10' as the color ramp for the '-false' coloring from blue to red.

lasgrid -in lidar.laz ^

            -last_only ^

            -step 5 -point_density_16bit ^

            -false -set_min_max 5 10 ^

            -o density_5_10.png

Make sure to use the '-keep_last' or '-last_only' filter if you want to count the pulse per square meters so you only use one return from every pulse.

Regards,

Martin @rapidlasso

 

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[mc...@u.washington.edu]

Not that you can't do the return count in LAStools but...

FUSION also has the ReturnDensity tool that can produce the return count raster in either FUSION's own DTM format or ASCII raster format. It is faster that Catalog and offers the option of ASCII raster data for downstream use.

Bob

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