Standard deviation of Z values in overlap area

[Mathew, Sojan]

I was just wondering whether it is possible to generate a raster file with the Standard Deviation of Z values in the overlap area between two adjacent flight lines or not.

Actually, I was curious to check whether there  are any variation in Z values from two different scan angle in the overlap area of two adjacent flight lines.

Thanks,

Mathew

[Martin Isenburg]

Hello Mathew,

It's not entire clear to me what you want to do. Assuming you have a tile where the point source ID is correctly populated so that each return from a different flight line has its flight line ID stored in the point source ID field. The you could simply run lasgrid once to generate the stddev of all first returns per 2 by 2 meter pixel:

lasgrid -i tile.laz -keep_last -step 2 -stddev -odix _stddev -obil

http://rapidlasso.com/lasgrid

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

then lasoverlap to generate an overlap raster that counts the number of flight lines per 2 by 2 meter pixel to show you where there is more than one flight line:

lasoverlap -i tile.laz -keep_last -values -no_diff -obil

http://rapidlasso.com/lasoverlap

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

and then use some raster calculation in QGIS / GDAL / GRASS / SagaGIS to cut out only those parts from the first raster where the second raster has pixel values of 2 or more. To correlate that to the (absolute?) scan angle maybe create another raster:

lasgrid -i tile.laz -keep_last -step 2 -scan_angle_abs -highest -odix _scan -obil

and then do whatever comparisons you want to do.

Regards,

Martin @rapidlasso

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