Re: [PulseWaves] Leica waveforms FWF in las 1.3?

[Ilkka Korpela]

Quoting Jason Stoker <jsto...@gmail.com>:

> All, we are having a collect done this summer by a contractor using
> a Leica instrument where the waveform is embedded into las 1.3 (no
> wpd files supplied). Is getting the FWF in las 1.3 going to be OK,
> or do you have any suggestions for other ways that the vendor can
> deliver the waveforms?

Hi

Our experience has been that the vendors have trouble establishing
the geometric corrections (inter and intrastrip-, and campaign-level)
while simoultaneously maintaining the integrity of the data, as the
DR data only is used for the estimation of trajectory/attitude corrections.
There does not seem to software that really supports FWF data (strip
matching, boresight calibr.) "Nobody asks for FWF data", is what we hear
often, and "Very few are even interested in the trajectory data".

Our solution (we do research) has been to have the DR data used for
strip matching /
trajectroy estimation, output LAS 1.2 DR data, and then take the waveforms
from LAS 1.3 files (without geometrioc corrections) and associate these,
using the time stamps between the LAS1.2 and LAS 1.3. This applies
to Leica sensors, for which LAS1.3 is well suited, as there is always
a single 128- or 256-byte sequence of amplitude data per pulse transmitted,
and no sampling of the outgoing pulse (to monitor its stability,
power over time)

With Riegl, the best way would be to use a dll by the company. Their
processing software doesn't well support LAS1.3 /WDPs (at least last
spring it didn't), because the time offset from the DR measurement
to the beginning of
each amplitude sequence (there can be several, multiples of 80 samples),
is only at 1 ns nominal accuracy. For such data comprising of multiple
WF sequences per pulse, WDP suits better. The company's own
dll for processing of the data, incl. the image of the transmitted pulse,
is probably a much better choice than using the blurred version in LAS1.3,
that also lacks the image of the transmitted pulse, which is what one
really needs in serious FWF analysis.

Saying that, we have not yet really found any real use (gain from)
for the WF data, that would pay for the extra storage and
computation efforts.
We are searching still :)

Would be interested in hearing about better solutions, me too.

Ilkka Korpela, Academy research fellow, Finland






> Thanks!
> Jason
>
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--
Ilkka Korpela
http://www.helsinki.fi/~korpela

[高崇軒]

Hello Jason

I'm assuming that you're wondering if the FWF data can be extracted in LAS 1.3 format. Our experience is yes, it can be extracted and work just fine. 

I'm just curious of what you're going to do with FWF data. Visualization? Or some application?

Cheers

Rock Kao

R&D Engineer

LIDAR Tech

2013/4/26 Ilkka Korpela <Ilkka....@helsinki.fi>

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Ilkka Korpela
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[Stoker, Jason]

Thanks Ilkka, that is very helpful!  Rock- one of our postdocs is getting this collection flown to do research on radiative transfer modeling for terrestrial carbon stocks.  Light extinction  through the canopy a major interest to her.  This is completely separate from any national-scale lidar mapping efforts that I have been involved with in the past.  Although small footprint waveform data for the entire U.S. would be interesting! ;-)

Jason M. Stoker

Physical Scientist

USGS Earth Resources Observation and Science (EROS)

47914 252nd St.

Sioux Falls, SD 57198

Office: 605-594-2579

Cell: 605-496-3513

My USGS Profile: https://profile.usgs.gov/jstoker

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[Martin Isenburg]

Hello Jason,

I agree with Ilkka suggestion for the most part. If the sensor that
was used to capture the full waveform LiDAR was a LiDAR sensor, then
(and only then) LAS 1.3 FWF is sufficient as there is no information
gain from using other formats. If, however, the full waveform was
captures with a Riegl, Leica, or AHAB scanner then I would go back to
the vendor and request the "rawest possible" format so that you have
the richest information possible when convert it to PulseWaves. To
make things easier in the long run, request your vendor to deliver in
PulseWaves in the future. (-: It seems RIEGL has more or less
completed PulseWaves integration, while Optech has promised to follow
suit (although its been a while I have heard back from them), and AHAB
once suggested to invite me up to Sweden to help with PulseWaves
integration ... although that might have been after a few beers.

If waveform is the main reason to do the LiDAR collect then I would
advise to make your contract spell out that a scanner is to be used
that also captures the outgoing waveform.

Cheers,

Martin @LaserPulseWaves

On Apr 26, 12:29 am, Ilkka Korpela <Ilkka.Korp...@helsinki.fi> wrote:

> > Visit this group's message archives athttp://pulsewaves.org