[GRASS-user] Re: Problem with Lidar Tools

[Mark Seibel]

On Tue, Dec 7, 2010 at 7:53 PM, benmarillier
<ben.marillier at water.wa.gov.au> wrote:
>
> Hi All,
>
> I am having similar problems to Kaipi in regards to the v.lidar.growing
> stage of LiDAR processing. I'm running GRASS 6.4.0 on Windows. My dataset is
> a 1km by 1km tile of LiDAR with a point spacing of about 1.5 points/m2, so a
> total of about 1.5 million in the area of interest.
>
> Thus far I've imported the points with v.in.ascii, split into the first
> returns and last returns. I interpreted these two classes as follows (please
> correct me if I'm wrong)...
>
> First returns: all first returns, including single returns where only one
> return has been received.
> Last returns: all single returns, and the last return where multiple returns
> have been received.
>
> Then I removed outliers as per the micro-tutorial on the GRASS wiki.
>
> Next I ran v.lidar.edgedetection on the last returns with the default
> parameters.
>
> This resulted in a reasonable looking classification of edge (2), not-edge
> (1) and uncertain (3). The edges of the buildings and trees are quite well
> defined, as shown in the image below, so far so good...
>
> ...however, when I run v.lidar.growing (default parameters), the output I
> get is exactly the same as the edgedetection output. The points are
> classified identically into 1, 2 and 3, and there appears to have been no
> change in the classification. I've tried varying the growing parameters, and
> changing the region resolution, but the output is always the same.
>
> I've trawled through the forums to no avail, so any advice would be greatly
> appreciated.
>
> Thanks,
> Ben



Hi.

Is this urban, rural, or mixed land use?

Mark