High Sierra Topix

Interesting article:
https://eos.org/features/a-lidars-eye-v ... are-faring

Thanks for posting this article, i really enjoyed it. Really cool to see how they are using data & technology. I met some guys doing work here in the eastern sierra using lidar in the last month, I think it was a study for ucsd, the company contracted was out of Oregon. I wonder if they have done any mapping in SEKI and seq national forest given all the fires and the severe impact to the forest. Thanks again really enjoyed it.

Sounds like a real improvement for veg typing over the older methods from aerial photos and sat imagery. LIDAR has been used for terrain models for years.

Well, serendipitously I just got a Topic Reply notice after long absence from HST. So I came by and, poking around, found this thread. Thanks for posting. Excellent reference and interesting approach.

I've been fiddling with lidar for a few years looking for ways to illustrate vegetation (aka fuels) in neighborhoods and communities. A couple of years ago a friend and I used 2011 lidar for Tuolumne County, CA to show relative density of "ladder fuels" in the 1m to 4m veg profile. I posted it in 3D here:
https://arcg.is/zPLPf

Here's a 2D map for Twain Harte (Google Drive link):
https://drive.google.com/file/d/1fnvGW3 ... sp=sharing

And, 'cause the fun never stops, lately I've been trying it again with just my neighborhood using our 2020 lidar data. ESRI's John Nelson has a terrific video of creating terrain data as dioramas, so I tried that. I also derived homes from the lidar and put those in. It's interesting and, I think, pretty cool but I'm not sure what it means or how it can be used:
https://drive.google.com/file/d/1fnQU8L ... sp=sharing

Another friend is teaching a fire prep class for PG&E and we're talking about using lidar of the area they're working in to better plan tactics and mitigation. We'll see. If there's interest here I'll post updates as they occur!

Meanwhile (and are we all having nerdy fun still?) Jim Schmidt (retired USFS fire/GIS nerd) has been working on estimating fuel density around structures lost in the Camp and 4 other fires. He started with lidar but has found that standard NAIP is just as good and that the relationship is with total fuel within 100' or so and less so with ladder fuels. This is depressing in that it suggests that clearing out around a house is not as effective preventing loss as we hope.

And (!!) another paper just out shows a strong relationship between housing density and loss as well as when the houses were built (pre-1987 building codes have a very high loss rate):
https://fireecology.springeropen.com/ar ... 21-00117-0

OK. No mas! It's fire season (not that it ever ends around here) so interesting to share and discuss different approaches at illustrating and, perhaps, mitigating danger and risk.

George

could these new lidar measurements eventually be turned into 21st century topographic maps?
the level of detail is staggering, and seems (to my feeble mind) like it could easily be transmuted into wildly accurate topos.

Right before I retired we started using multispectral imagery for bathymetry. By manipulating the UV bands we could determine depths and contours of wilderness lakes. I left before really getting into it, though.

Also using IR bands to find unmapped lava tubes.

I left right when it was getting fun.

I did use DEM data (Digital Elevation Model) to make 3 meter contour maps. They ended up being less useful than we thought they would.

Arrrghhh. Wrote a long and brilliant reply but had been logged off and <poof> it disappeared when I went through the Submit/Login process.... . I'll try again but it won't be as good (!).

@frozenintime Embarrassingly, I'm not sure how USGS makes topo maps today. In the olden days (up to the 70s) it was incredibly labor-intensive in that each contour line was hand-drawn from satellite imagery. In the 70's I ran into a cartographer in the Upper Kern on the JMT who was ground truthing a new Whitney Quad. Writing down assorted peaks, vegetation extent, trail location. What a great job! (though mine was pretty good, of course...).

I assume today it's mostly satellite imagery at various bands (the spectrums the satellite uses, e.g. IR and RGB etc). Lidar has to be specifically flown for an area. It's getting into wider use because the price is coming way down. All of Yosemite was flown last year and I think Sequoia Kings has been flown. Satellite imagery can give really good terrain and vegetation as @dave54 points out above. So that's what being used now for USGS maps. You can also do smaller areas of lidar from handheld drones.

I didn't know you could get lake depths. That makes sense and is very cool. What sort of accuracy? There's also really good sea floor surface maps and I'm not sure how those are derived/mapped. @dave54 or anyone else? Assume local areas have been done by surface ships but worldwide? Can satellite do that?

When we were looking for a missing skier a few years back I tried to find out if lidar or other imagery could show a person suspended in avalanche snow but no, alas. I wonder if bathymetry techniques are good enough to see an aircraft at the bottom of a body of water?

But, next, here's my latest effort just used yesterday in a fire effects class a friend is teaching. The idea is to show terrain and vegetation heights of a discrete area of terrain. So, bare earth, 1m, & 4m (ladder fuels); and > 4 meters (trees). This shows what's called the point cloud for the veg -- the actual pings sent down and reflected back to the aircraft so you can see the actual shape of the trees. I also derived buildings from the lidar.

https://www.youtube.com/watch?v=BfQrZLwLmAM

Dweeby side note, I also tried other techniques showing veg height by creating various surface models (DSM's & DEM) which worked pretty well. If anyone's interested, I can give you the tech workflow. Also, if anyone has other ideas I'd love to hear them!

OK. More than anyone probably wants to know but looks pretty darned cool. I also just ordered 32GB of RAM. This stuff just sucks down processor power... . And, oh yeah, I'm retired so just tinkering with this rather than yelling at kids to stay off my lawn... .

George