Hello Kutalmis;

So you are saying that commercial WF recording systems are in use over there in TX and that your university has a dual-band sensor. Congrts!

The point that I tried to make was more about commercial topographic sensors, the sensors that are being used for mapping purposes. We have used these sensors since about 2004-05 for characterizing trees and forest canopies, and I'm curious about the markets in 2020: if one wants to have large coverage (hundreds of sq km) airborne LiDAR data, with WFs stored for each pulse transmitted, is it still possible as it was in my country 2010-2017. The hype now seems to be about very sensitive systems that need just a few returning photons, using which you get a dense (and noisy) point cloud from a high altitude, which reduces data costs.

The current palette of commercial (discrete-return) sensors may still have those that can be harnessed with WF recording option, but are these bought by the companies, ie. in use and available for experimenters (without the need to be sky-high prices)?.

ilkka

Most definitely there are the sky high prices to match the sky high data rates and full waveform recording features that are available but not just in the very largest airborne scanner from Riegl with dual beam at 1064nm and 532nm and 2 million points per second. Riegl also provide the full waveform data capture in the full range of scanners down to the VUX-1HA which has 3mm accuracy.

The key difference between this method and the single photon method you mention is just that with single photon you can indeed capture a much wider swath from higher flight path and so get higher productivity from each hour in the air, but single photon is no good at all when there is vegetation on the ground, it cannot provide the differential between treetop and ground profile with enough clarity to obtain a ground surface model accurately.

Using even the much lower end Minivux-1 or minivux-2 from Riegl each with up to 5 returns per point and flying just a UAV you can easily get cm level survey data and get clean terrain model including vegetation detail to provide volume and growth data.

contact me [email protected] to get more info if needed

thanks Randall. Yes, I know that many of the manufacturers have the option to install the WF digitizers in the receivers, but these are, ss far as I know, add-on gadgets that cost quite a bit.

I'm trying to find people who can say if such sensors are actually in use in 2020, or is everyone operating DR sensors without the WF recording option?

Having WF recording switched ON may influence the doable pulse density. At least in the (ancient) ALS60, which had two oscilloscopes taking turns in sampling the WFs, there was an upper limit in PRF (about 115 kHz) after which you got only 50% of the returning pulses digitized. This may well be the case in the moder sensors as well. The digitizers and busses can't keep up with high PRF.

But, again, do companies who fly LiDAR data have these sensors anymore? Are they buying the optional digitizers to the sensors that otherwise only collect discrete-returns. In 2018 I got some riegl1560i data, but the (BIG) company said that they did not have the WF option, nor for the Optech Titan, which could be equipped with 2 digitizers that listen to 2 out of the 3 receivers (532,1064, 1550 nm).

I have played with Riegl LMS-Q680i that is a true WF sensor as the WFs comprise the stored observations. But that sensor seems to be outdated. The WFs are cool, here's an example with old 2013 WF data:

http://mires-and-peat.net/pages/volumes/map26/map2603.php

Cheers, ilkka

We use WF lidar for vegetation applications. Yes, they are very informative. I used them for dryland vegetation characterization. We don't own a sensor. We used/use data collected from LMS Q1560 (NASA JPL) and National Ecological Observatory Network's (NEON) LMS Q780 data. NEON data is freely available.

Thank you Nayani. The Q1560 is available in Finland as well by a company in Norway, but they do not have the WF-recording option bought and installed, so its DR data that I'm going to collectt his summer.

I did not know of NEON. Looked at the site. Great collaboration.

All my reserach is near https://fluxnet.fluxdata.org/doi/FLUXNET2015/FI-Hyy and I have LiDAR since 2004, nearly every year. It's just that WF sensors do not seem to exist (commercail) anymore in Northern Europe. Flying one from far away is really expensive.

Thanks again, ilkka

You are very welcome. Thanks for sharing your research and I have used some of your findings for my research (Thank you!). About NEON; they revisit their sites with full payload (hyperspectral, lidar (discrete and waveform), and camera) every 1-2 years.

In the Czech Republic, it is possible to use the Riegl LMS Q780, which is owned by CzechGlobe - Global Change Research Institute CAS. It can also be used for commercial applications as well as in foreign countries. Link: http://olc.czechglobe.cz/en/main-page/

We use data from this scanner for our university forest enterprise (10 000 ha).

Zdenek Patocka this is good to know. Riegl 780, 680 were (are) good sensors and work with those was (is) based on WF postprocessing. It seems as if the larger companies have gone for more efficient ones (flying costs) and therefore no WF from their part. Thanks.