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Gary-Shaw / bcal-lidar-tools

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height filtering in xyz to las converted files #5

Closed GoogleCodeExporter closed 9 years ago

GoogleCodeExporter commented 9 years ago 
After conversion of ascii xyz lidar data to las format I permormed height 
filtering.
The las file obtained as output has been then used to trace elevation profiles. 
The obtained profiles show coincident transects for vegetation and bare earth, 
as if height filtering didn't work. I tried to apply the same procedure also to 
a native las file (not coming from a xyz conversion) covering the same area and 
the result obtained is what I expected to get, with two distinct lines for 
vegetation top and bare earth.
I'm using BCAL Lidar tools 1.4.2 with Envi 4.8 on winXPPro.
Thanks again.
Flavio

Original issue reported on code.google.com by f.pogg...@gmail.com on 19 Dec 2012 at 3:39

GoogleCodeExporter commented 9 years ago 
Use 'Ascii to LAS' tools from version 1.5.0. It allows you to specify your own 
scaling and offsets. This should take care of filtering issues. See Issue#4 for 
more info.

Original comment by shrer...@isu.edu on 20 Dec 2012 at 9:20

GoogleCodeExporter commented 9 years ago 
ok. I'll download and install this new version and try it.....maybe after
xMas holidays...Thank you for kind asistance and support, and my best
wishes to you all.
Flavio

Original comment by f.pogg...@gmail.com on 21 Dec 2012 at 7:25

GoogleCodeExporter commented 9 years ago 
hi. Here I am again. First of all, best wishes for a lucky 2013!
Then, I downloaded and installe the new plugin version and I'm testing it
with my data. I'm stil registering some troubles.
First I had problems in the file conversion process from xyz to las format:
in order to get a positive result I had to try different x, y and z
scaling, since, with the default setting to 0.01 the las file I got in
output couldn't be opened with the 3d viewer. Then I tried with a 0.001
setting and it seems to work, even if I still have to provide a coordinate
conversion from geographic to UTM projected to visualize it properly
(otherwise I get a vertical line of dots).
Then I tried to extract a linear profile, so I processed the las file with
the height filtering tool and previously I created a profile line with
QGis. The profile line in shp format, was then imported in envi and
converted in evf format: I've verified the file coordinates, and they seem
to be correctely in UTM_wgs84 32N format. Yet, when trying to extract the
elevation profile with the bare earth line, I get an error message back,
telling me that there aren't enough points around transect1, as if there
would be projection problems with the 2 files (las and evf).
Help, please!!!!
Thank you.
Flavio Poggi

2012/12/21 flavio poggi <f.poggi68@gmail.com>

Original comment by f.pogg...@gmail.com on 11 Jan 2013 at 9:39

GoogleCodeExporter commented 9 years ago 
Hi Flavio - Have you try using lastools (lastools.org) to convert ascii to las?

Original comment by shrer...@isu.edu on 19 Feb 2013 at 4:02

GoogleCodeExporter commented 9 years ago

Original comment by shrer...@isu.edu on 11 Mar 2013 at 2:11