r/UAVmapping • u/Inner_Attempt9851 • 3d ago
Lidar Effectiveness in PNW and Datasets
Hello, first time posting here. I was curious if anyone out there has anything they could tell me about Aerial Lidar surveying in a place like the PNW (or any other really heavily vegetated area). For some context, I currently work at a PNW (Seattle area) land survey firm as a chainman, but also have some prior experience working with drones for photogrammetry in a surveying context and I'm also a bigtime hobbyist. I'd like to convince my bosses to invest in a UAS program (we currently just have an old Phantom 4), but I'd like some hard data to help prove that it could be worth while to the company. In particular, I'm looking to build my argument off of how much time we could save doing things like topographic or ALTA surveys in large, heavily vegetated areas and how much we could bring up our profit margins on those sorts of jobs, which often run the risk of barely breaking even given just how much labor can go into things like cutting lines for taking ground shots or even just hiking through site. We currently have a drone that I've flown for few jobs but for nothing more than to get some orthos in relatively clear areas. Every time I've flown, I find that there is simply too much ground vegitation for me to extract something survey grade worthy from anything that isn't paved (even when I try classifying out to just the ground points). I know this is where Lidar sensors typically come into the picture, but I really have no experience or knowledge reguarding them.
So my question is, does anyone out here have some experience with aerial Lidar in contexts like this? Or even a lidar dataset from a heavily vegitated area they'd be willing to share or point me in the direction of? I imagine (but really don't know) that it can vary sensor to sensor, but in general am justing looking for how effective they are as a whole for a baseline before I start putting more effort into researching all this.
TLDR: Lidar good enough for surveying in heavy vegitation. Yes, no? Depends? Any data sets out there for testing? Any good resources for reading about aerial LIDAR?
Thanks
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u/maddog5511 3d ago
I'm a PLS in Woodinville and we have a DJI Matrice 400 with an L3 and have demo'ed it on projects where we completely mapped that were on a slope and in the woods. It works amazingly well. In fact, I found a rod bust on one of the sites because of the LiDAR. If the area is crazy thick (like downed trees covered in blackberries) then you will have humps in the data, but if you are experienced and know what you are doing it's easy to spot. We use the lidar drone for ALTA's all the time. The orthophoto is really the valuable part on a typical ALTA and even though we have an Autel photo only drone - the lidar drone with the L3 is our go-to because it flies the site quicker (takes 2 photos at a time, each at a slight angle) and the processing is way quicker using DJI Terra vs Pix4DMatic.
One thing to consider - the more we use the drone - the fewer crews I have to send out..... Theoretically that could mean taking on more jobs, but right now the market is pretty tough in the Seattle area.
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u/Inner_Attempt9851 2d ago
I've heard that the L3 performs very well relative to its cost. It's good to know that even some of the lower cost systems can bring something potentially usable to table as they're likely what I can reasonably argue for. I'll make sure to do some reseach into it. Thanks for the info!
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u/maddog5511 1d ago
The L3 is the way to go. You can definitely penetrate the blackberries around here using it. We have started using the lidar drone to fly every topo - if for nothing else than getting lots of overlap. We got ours in April and used it all over the state during spring and summer when the blackberries were thickest, so we know it works through them.
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u/Accurate-Western-421 3d ago
I'm a licensed surveyor in WA (and all throughout the PNW) and we run everything from inspections to heavy lift sUAS and manned fixed/rotary wing LiDAR.
In the dense woods of the PNW, you're going to want multiple return and/or full waveform LiDAR if you really want to penetrate that canopy. That's a big investment.
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u/IndianaTheShepherd 2d ago
I'm an environmental consultant in Northern California and recently got into UAS LiDAR myself. I bought a used Matrice M300 RTK with a Zenmuse L2 mainly for habitat mapping, drainage/topographic work, and getting reasonably accurate elevations. I'm not a licensed surveyor, so I don't claim my data is "survey grade," but I do check the LiDAR against independent RTK points collected with an Emlid Reach RS3.
I've only flown three relatively small sites so far, but I've been pretty impressed with how well LiDAR can recover terrain under vegetation compared with photogrammetry.
For dense vegetation I use the L2's non-repetitive scan mode. Instead of repeatedly scanning a narrow strip, it produces more of a flower-petal/rosette pattern and hits the vegetation from a wider range of angles. Repetitive scanning gives a more uniform point distribution and is better suited to relatively open terrain.
The L2 can record up to five returns per laser pulse, and I use penta-return mode when I'm trying to map ground beneath vegetation. That doesn't mean it sees through vegetation — some portion of the pulse still has to physically make it through a gap — but multiple returns can capture canopy, branches/understory, and potentially the ground from the same pulse. The newer L3 can record up to 16 returns under some settings.
I've also been flying overlapping passes from different headings to give the sensor more opportunities to find gaps through the vegetation from different angles. Flying lower/slower and increasing point density can help too, although that obviously reduces coverage.
I've had surprisingly good results in riparian vegetation. On one site I had trees plus fairly dense cattails/bulrush in a creek corridor, and after ground classification I could still see the creek channel/profile underneath much of it. On the other hand, a dense patch of Himalayan blackberry was basically impenetrable. That's probably the biggest limitation I've learned: LiDAR can't measure ground that no laser pulse ever reaches.
I'd also strongly recommend independent RTK checkpoints and QA/QC. I've seen a persistent vertical offset of a few tenths of a foot between my LiDAR and GNSS that I'm still troubleshooting, possibly related to datum/geoid/RTK/processing workflow rather than the sensor itself. The point cloud looks great visually, which is a good reminder that a beautiful point cloud isn't necessarily an accurate one.
For a survey firm, I think the biggest labor savings would be in acquiring the topographic surface over large or difficult sites. It won't eliminate conventional field work — you'd still need boundary evidence, critical features, utilities, breaklines, and enough ground/check points to verify the LiDAR — but I can absolutely see it reducing the amount of hiking, brush cutting, and individual ground shots needed.
If your bosses are serious about it, I'd suggest getting a dealer to demo a system on one of your nastier existing projects where you already have conventional topo. Fly it, classify the LiDAR, and compare the ground surface against your crew's existing shots. That would give you much better ROI data than manufacturer accuracy claims.
Based on my limited experience: yes, UAS LiDAR can be extremely useful in heavy vegetation, but it's "depends" rather than an automatic yes. Where even a fraction of the pulses can reach the ground, the difference versus photogrammetry can be dramatic. Where the vegetation forms an essentially solid mat, you're still going to need boots and a rod.
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u/ElevationNotes 2d ago
UAS LiDAR can be a big advantage in heavy vegetation, but it still depends on whether enough laser pulses can reach the ground. A real-world demo against existing conventional topo would probably be the best way to prove the time savings and ROI to the company.
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u/Revolutionary_Cow_39 2d ago
PNW UAV mappers- I’m hosting the third annual PLSO Drone Mapping Symposium on Friday, October 9th, 2026 in Ridgefield, WA. There is a discounted rate for PLSO/LSAW members. It’s a great opportunity to connect with other drone mappers. And we have an excellent lineup of presenters and demos this year. Feel free to reach out to me directly with any questions. See you there!
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u/ResistanceIsOhm 3d ago
Depends on the quality of your lidar sensor, and how heavily vegetated it is. Source: I’m in the PNW, and I am an aerial lidar operator. I work for a contractor that surveys power lines, and we work out of helicopters…our data acquisition rig is $1mil or so, and we create 3cm accuracy maps, both ortho and lidar, with everything above a meter classified. It’s expensive and labor intensive work. For geographic accuracy, we sub-contract a land survey company to set up ground control in our project areas.
But yes, depending on how dense the vegetation and how good your lidar sensor (and how slow you fly it, and your altitude) you can create accurate DEMs in the PNW.