[GRASS-user] Classified point cloud from UAS

[Nuno Sá]

Hey Anna

Yes, I thought of that but the coarse models I would have access would be
the STRM which has 10m vertical accuracy, plus that is Height above
ellipsoid I think, so I would have to convert it using the geoid ondulation
meaning I would have another error (or am I mixing topics here?). So
besides all the difference between data I would have increasing error
sources in everything.

Making a DTM based on random points on locations where I know the ground is
would lose the ability to detect height variations within high canopy
covers but could be an approach since ground heights are otherwise
unavailable?

All the best!
Nuno



On 15 May 2015 at 20:45, Anna Petrášová <kratochanna at gmail.com> wrote:

>
>
> On Fri, May 15, 2015 at 10:35 AM, Nuno Sá <nunocesardesa at gmail.com> wrote:
>
>> I've got the same questions :)
>>
>> How will you get the DTM if you don't have info on the ground ?
>>
>> I did some search for publications but couldn't find if there were any
>> methods just by using UAV data, do you have any recommendations?
>>
>> Ciao!
>> Nuno
>>
>> On 15 May 2015 at 14:40, Adam Laža <ad.laza32 at gmail.com> wrote:
>>
>>> Hi all,
>>>
>>> I've got some data from UAS (SenseFly eBee) exported as point cloud. I'd
>>> like to ask if there's any way how to classify the data in GRASS. As an
>>> input I have a point cloud exported in .las or .txt file. As an output I
>>> need another .las file containing only terrain (I need to filter out
>>> objects, buildings and vegetation) for next step which is generating DTM.
>>>
>>> I've already tried some modules, import(r.in.lidar, v.in.lidar) works
>>> well. Then I focused on v.lidar.* modules (v.lidar.edgedetection,
>>> v.lidar.growing, v.lidar.correction) but already the first step of
>>> recognizing and extracting object didn't work for me. I suppose it's due to
>>> the v.lidar.* modules need data only from LiDAR, but I have data from
>>> phtogrammetry (eBee carries Canon RGB camera).
>>>
>>> Any idea how to classify my data?
>>>
>>
> Hi,
>
> I haven't tried v.lidar.* modules, because I typically work with already
> classified lidar, what exactly was the problem?
>
> Generally, you it would be difficult to get ground from UAV data because
> the point cloud represents only surface (unlike lidar where you get
> multiple returns). You could compare the point cloud with some coarser
> digital terrain model and high differences would mean that there is some
> vegetation or buildings.
>
> Anna
>
>
>>> Thank in advance,
>>> Adam
>>>
>>> Data sample at google drive:
>>> las:
>>>
>>> https://drive.google.com/file/d/0B3qa8r8b0sq0TTdnSVNHdE1UQ2M/view?usp=sharing
>>> txt:
>>>
>>> https://drive.google.com/file/d/0B3qa8r8b0sq0NVFRMmNEZHNkbDA/view?usp=sharing
>>>
>>>
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>>>
>>
>>
>>
>> --
>>
>> Nuno César de Sá
>> +351 91 961 90 37
>>
>>
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>>
>
>


-- 

Nuno César de Sá
+351 91 961 90 37
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