Fullwaveform LiDAR for forestry application

[Nurul Ain]

Hello,

I have several question that i would like to ask, and get some clarification .I'm a newbies in this LiDAR processing, and would like to have your answer regarding to this matter.

1.How to analyze fullwaveform lidar data? In what format that usually used?

2.How about the projection used to process the fullwaveform Lidar data?(For an example from UTM47 to GDM2000 or vice versa)  How to do the re projection using lastools?

Hope to hear your answer.

Ain

[Jonah Sullivan]

I have seen many RESEARCH projects utilising full waveform lidar. I have never seen a PRODUCTION usage (a real-world survey with a reasonable study area).

Most of the research has used matlab.

Martin Isenberg has created Pulsewaves to query full waveform data packets, but I have never seen it used in the wild except for research projects.

Jonah Sullivan
Geospatial Analyst
National Topography Services | National Location Information Group
Environmental Geoscience Division | GEOSCIENCE AUSTRALIA
Phone: +61 2 6249 9516 Fax: +61 2 6249 9999
Email: Jonah.S...@ga.gov.au Web: www.ga.gov.au
Cnr Jerrabomberra Avenue and Hindmarsh Drive Symonston ACT
GPO Box 378 Canberra ACT 2601 Australia
Applying geoscience to Australia’s most important challenges

[Antoine Cottin]

Hello Ain,

To answer your questions:

1. To analyze the waveform you have to basically develop your own tools or use some existing tools that have been develop with PULSEWAVES.

2. Projection is not related to waveforms… in LAS file usually the waveform is tie to a point of the point cloud… and actually this point is derive from the processing of the waveform. The waveform is a basically a electrical signal recorded over time with no geographical information… the geographical information comes from an anchor point and a direction vector. If you want to change the projection, you have to transform the anchor points coordinates accordingly. 

More information about waveforms:

Waveforms come mostly in two flavor, LAS (1.3 and 1.4) or PULSEWAVES. You can find other type of formats but they are not as widely accepted as these two format. But LAS is not really adapted to full-waveform data… this is why Martin Isenburg develop the PULSEWAVES format. A C++ reader/writer is available on Rapidlasso's Github:

https://github.com/PulseWaves

Carbomap as developed a PULSEWAVES reader/writer in IDL and is available on its Github repository:

https://github.com/carbomap/PulseWaves

With Pulsewaves you’ll have some limited tools to analyze the shape of the waveform.

If you have LAS file with waveform than you can use Carbomap's tool, fleurdelas, which has functions to get access to the waveform:

https://github.com/carbomap/Fleurdelas

As Jonah said, waveform is not widely used yet in the industry as standard data, as it’s difficult to handle (big data) and time intensive to analyze. Historically, the community that uses waveform in production are the hydrographers using airborne bathymetric lidar. 

Coming from this community, I have a long experience in full-waveform processing and have develop Carbomap’s processing tools and workflow around the waveform. So, as of today, we use, on a daily base, in production full-waveform for forest mapping.

Don’t hesitate to contact us if you have questions.

Cheers.

Antoine 

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Dr Antoine Cottin
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[Daniel Clewley]

Hi Ain,

If this is the ARSF full waveform LiDAR data you emailed about earlier
it will be LAS 1.3 format which contains the point data (1st, 2nd 3rd
and last return) and the digitised waveform for each Pulse (we also
supply LAS 1.3 format data which doesn't have the waveforms). LAS 1.3 is
used as it is the only format Leica's software exports. The projection
of the points will be UTM but you can reproject them using LAStools.

You can download a sample of ARSF full waveform data from
http://liblas.org/samples/NERC-ARSF-LAS1_3-sample.tar.bz2 or full
projects from http://neodc.nerc.ac.uk/ (application required).

You can use the LAS 1.3 files in LAStools to create a DSM/DTM etc., but
they won't make use of the waveform information only the points. As
Jonah and Evon suggested PulseWaves is capable of working with the
waveform information in LAS 1.3 files (and other formats) and
'pulseview' is capable of visualising waveform data. There is a separate
mailing list for pulsewaves where there is more discussion on
full-waveform data.

There are also some other packages which can work with waveform data
(open source and commercial), we have some listed here
https://arsf-dan.nerc.ac.uk/trac/wiki/Links. (open to more suggestions
on these). However, depending on what you want to achieve it's likely
you'll have to write something yourself.

Hope this helps,

Dan

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[Jan Depner]

Dan,

I downloaded your LDR100301_120340_4.las to take a look at some
waveform data. I am a bit confused though. When I run lasinfo on the
file I find:

variable length header record 4 of 5:
reserved 43707
user ID 'LASF_Projection'
record ID 34735
length after header 56
description 'Projection Info'
GeoKeyDirectoryTag version 1.1.0 number of keys 6
key 1024 tiff_tag_location 0 count 1 value_offset 1 - GTModelTypeGeoKey: ModelTypeProjected
key 1025 tiff_tag_location 0 count 1 value_offset 2 - GTRasterTypeGeoKey: RasterPixelIsPoint
key 3076 tiff_tag_location 0 count 1 value_offset 32632 - ProjLinearUnitsGeoKey: look-up for 32632 not implemented
key 2052 tiff_tag_location 0 count 1 value_offset 9001 - GeogLinearUnitsGeoKey: Linear_Meter
key 4096 tiff_tag_location 0 count 1 value_offset 5030 - VerticalCSTypeGeoKey: VertCS_WGS_84_ellipsoid
key 4099 tiff_tag_location 0 count 1 value_offset 9001 - VerticalUnitsGeoKey: Linear_Meter

My problem is that it appears that key 3076 (ProjLinearUnitsGeoKey) with
a value of 32632 (which is undefined for ProjLinearUnitsGeoKey) should
probably be 3072 (ProjectedCSTypeGeoKey) for which the value 32632 is
defined as PCS_WGS84_UTM_zone_32N. Is that correct? I hope so,
otherwise I'm not able to determine UTM zone ;-)


Cheers,
Jan

[Daniel Clewley]

Hi Jan,

Yes the projection is WGS-84 UTM 32 N.

This is quite an early sample (2010) of the data exported from Leica's
ALSPP software. I believe there were some problems with correctly
setting the projection.

Thanks,

Dan

[Nurul Ain]

Hi guy,

I have another question, how can we verify the lidar data, whether fullwaveform or not? Is it any data that output from Riegle Q560 sensor will be consider as waveform data or any special characteristic that will be consider a waveform data? I have buy a data from a local company, but they claim their data is fullwaveform, but it is in las1.2 format.

Cheers,

Ain

[Antoine Cottin]

Hi Ain,

As you said, LAS 1.2 doesn’t hold waveform information.

Indeed Riegl sensors have a technology called ‘online waveform processing’, which means that for most of the scanner a waveform is indeed digitised than processed directly in the scanner and the discrete points are stored in the LAS file. Of course some sensors can also record the full-waveform.

Having a quick look at LMS-Q560 and it stated “full waveform analysis for unlimited number of target echoes”…

So claiming the data is full-wavefrom is true and false. If you clearly asked for full-waveform data associated to the points cloud, meaning LAS 1.3 or 1.4 or pulsewaves, then they didn’t delivered what you’ve expected… if you didn’t clearly stated that you needed the full-wavefrom data block… well… I’m not quite sure you can argue because the data you received is the result of full-waveform data.

Cheers.

Antoine

-------------------
Dr Antoine Cottin
Chief Technology Officer

Carbomap Ltd

7th Floor, Appleton Tower
11 Crichton Street
Edinburgh
EH8 9LE
http://www.carbomap.com

+44 (0) 131 668-6954

[Evon Silvia]

Whether or not your data was collected in full waveform depends on the sensor type, sensor configuration during acquisition, and post-processing. For example, just because a Riegl QG-820-G can record full waveform doesn't mean that they did record, or that they recorded it for every point, or that it wasn't lost during post-processing.

Back to you example, though... LAS 1.2 files are incompatible with the storage of full waveform data unless they separately stored it in the Pulsewaves format.

Evon

[Martin Isenburg]

Hello Nurul,

I encourage you to a watch a few minutes of this video (starting at time 2:18:13) and you should get a good idea about the difference in data and the confusion that exists about *true* full waveform and full waveform-derived discrete returns:

http://www.youtube.com/watch?v=_zBAaN6SO20&t=2h18m13s

Then continue on to this video and skip to time 3:09:30 where you can follow me doing a long and detailed visual exploration of full waveform data stored in PulseWaves format.

http://www.youtube.com/watch?v=e41kTmFdS_M&t=3h09m31s

You can download the data and the PulseWaves viewer here:

http://github.com/PulseWaves/

http://github.com/PulseWaves/PulseWaves/archive/master.zip

Regards,

Martin @rapidlasso

PS: We'll also be at the RIEGL LiDAR 2015 user conference in Hongkong and Guangzhou (May 4th - 8th) and at the Optech ILSC 2015 user conferene in Toronto (June 9th - 12th) to talk about what's new with PulseWaves.