Flying lasers eye naked earth
July 29, 2012 12:42 PM   Subscribe

Flying Lasers Reveal Buried Historical Structures (pictures)

It's LIDAR ("light detection and ranging"), which uses lasers in helicopters/drones and software to remove vegetation and reveal the naked earth surface with resolution down to centimeters. A brief history of LIDAR.
posted by stbalbach (23 comments total) 11 users marked this as a favorite
The second link requires Flash, but the first link has a great non-Flash gallery linked at the bottom.
posted by yoink at 1:01 PM on July 29, 2012 [2 favorites]

Absolutely amazing stuff! Interesting how the vegetation still shades the outlines on some of these remains after all these years. Either there are soil changes due to disturbance or these sites have been in continual use for eons. I lubs me some science.

The scientist does not study nature because it is useful; he studies it because he delights in it,
and he delights in it because it is beautiful. If nature were not beautiful, it would not be worth
knowing, and if nature were not worth knowing, life would not be worth living.
Jules-Henri Poincare

posted by BlueHorse at 1:11 PM on July 29, 2012 [1 favorite]

Oh cool, yeah I've been using Lidar in my archaeological research for a while. Where I work, you typically wouldn't directly detect an archaeological site itself (even with ~25cm vertical and ~50cm horizontal resolution) - they tend to be buried under recent soil and/or be fairly small sites in their own way. But Lidar is amazing for stripping off the dense rainforest, leaving behind a bare earth model produced by selecting only those laser point returns which come from the earth, not the vegetation cover. (This is done by a complex algorithm and a lot of tweaking by hand)

Here's an example - in this picture you can see a large area in a normal satellite view showing tops of trees -- some landforms are visible but coarsely, on the right you can see ancient shorelines from when sea levels were higher. In this picture is detail of the hill to the lower right of the previous, and with no trees you can see it as a sort of deeply-dissected mesa. With that model in hand we were able to waltz in and find sites up to 7000 years old on ancient shorelines in just a day or two, whereas even 10 years ago that would have taken something like a month and a huge dose of luck. In fact, we've used this around the place looking for the oldest of the old sites with quite a bit of success. It makes old-fashioned archaeological reconnaissance seem positively quaint by comparison (note - these pictures are really degraded resolution from the originals)

The downside is, it's extremely expensive to get flown, and a lot of the existing Lidar is owned by companies who won't share. I suspect that'll change a lot in the next year or two.
posted by Rumple at 1:19 PM on July 29, 2012 [15 favorites]

I wonder if the LIDAR unit would be something small enough to be flown on a quad copter or RC plane.
posted by smoothvirus at 1:26 PM on July 29, 2012

Very cool. Thanks for posting this.
posted by homunculus at 1:35 PM on July 29, 2012

Interesting that they found so many sites in the Black Forest. It really shows that Germany (and all of Europe) is an environment that has been inhabited and reworked by humans for thousands of years. No doubt the same is true for great forests in other areas like the Amazon.
posted by Kevin Street at 2:37 PM on July 29, 2012 [1 favorite]

I use LIDAR in two ways; first, the terrain way for doing roughness work for wind farm planning (and you wouldn't believe how badly it handles a field with standing cattle ...), and secondly pointing up to to give an instantaneous reading of wind speeds in a cone ~200m high. It's kind of magic.

smoothvirus, LIDAR has fairly hefty power usage. The smallest units I use are about the size and weight of a partially-loaded minibar fridge.
posted by scruss at 3:02 PM on July 29, 2012

It's kind of magic.

No, just sufficiently advanced technology.
posted by eriko at 3:20 PM on July 29, 2012 [6 favorites]

Hmm - oops... so I've been confusing LIDAR with Ground-Penetrating-Radar all these years - good thing I didn't go into geology... (or pretty much any job where I would be aiming high-power microwave beams in specific directions...)
posted by jkaczor at 3:55 PM on July 29, 2012

inhabited and reworked by humans for thousands of years

Quite a lot is known about humans who inhabited Northern Europe for the past 10 thousand years or so. You'd think that prior to the Romans and written records it's a sort of a dark uknown of barbarian tribes, but a lot has been uncovered through archaeology. Recommend the book Europe Between the Oceans: 9000 BC-AD 1000 for a (pre) history of Europe.
posted by stbalbach at 4:46 PM on July 29, 2012 [4 favorites]

Oh, Flying Lasers, is there anything you can't do!!
posted by etc. at 5:14 PM on July 29, 2012 [1 favorite]

And in other archaeological news: Archaeologists uncover Palaeolithic ceramic art
posted by homunculus at 5:49 PM on July 29, 2012

Hidden Doggerland underworld uncovered in North Sea

Wow, that could be an FPP all by itself, homunculus! Or at least it's a subject deserving of one. Don't know if there's much out there online.
posted by Kevin Street at 6:45 PM on July 29, 2012

> No, just sufficiently advanced technology.

I kind of asked for that, didn't I? Despite understanding exactly how it works, there is something semi-magical about setting up an atmospheric LIDAR unit, and being able to instantly see all of the wind flow vectors in three dimensions up to a seriously decent height.

Measuring wind speed - just horizontal wind speed - is hard with traditional equipment. Typically, you need a tower. Now, if you're only measuring at WMO-standard 10m height, it can be on pretty much anything - there are pump-up pneumatic towers that mount on the back bumper of a Land Rover that'll do that. Anything over 30m needs a semi permanent tower with fixed instruments. Anything over 80m starts to get huge, expensive, and needs air obstruction lighting (and lightning protection). Your measurement heights and locations are fixed. But you can have a LIDAR in the back of a truck, and move it from site to site, with a few minutes spent setting up. That's the magic part.
posted by scruss at 6:51 PM on July 29, 2012 [1 favorite]

I was secretly hoping "Buried Historical Structures" would mean "giant statues of squids deep below the desert" or "strange previously unknown undersea city"...
posted by woolly pageturner at 9:36 PM on July 29, 2012

Oh you guys with your flying lasers, what will you think of next?

I'm not sure which is cooler, finding archeological sites or mapping wind vectors. I shall have to spend a day following each of you guys around, obviously.

Rumple, where is the location in the pics, and what exactly did you find there?
posted by BlueHorse at 10:47 PM on July 29, 2012

Scruss: Low power and smaller units now exist (blessedly with onboard computers!). As someone who has routinely lugged 40kg of LiDAR (plus 40kg of computer and battery) up far too many mountains, this is a very very good thing.

Back of a truck? Pure luxury! ;)
posted by grajohnt at 1:39 AM on July 30, 2012

Frickin'flying lasers
posted by kcds at 5:25 AM on July 30, 2012

Ah, grajohnt, I wasn't aware. The smallest ones in use in the wind industry are bar-fridge sized, probably to deter theft. Wind power is usually in kinda hilly areas (except Texas and Denmark), and we nearly always have access roads for a crane, so trucks it is. Not used one of the forward-scanning LIDARs yet in any installation.

I have lugged in an entire WMO standard station (tower, guys, anchors, sensors, logger, cabling, plus tools and setup equipment) up a mountain single-handed, then installed it. Didn't enjoy that much at all. Nice view, though.
posted by scruss at 5:25 AM on July 30, 2012

bluehorse -- that is NE Haida Gwaii, the archipelago formerly known as the Queen Charlotte Islands. In that locale the early stuff was just a spread of simple stone tools buried about a metre down on a terrace overlooking the confluence of two of those deeply cut ravines. Charcoal from that layer gave the radiocarbon date estimate. An obvious spot for an archaeological site, but one that just stumbling around in the very dense forest would have taken forever to find. Instead, with the Lidar model, we could just set a waypoint and walk to that very highest potential spot and expend our energies digging not bushcrashing.

Lidar is really used for everything these days - police 'radar", obviously, survey instruments (that is, electronic transits, cluster total stations, robotic total stations, to calibrate telescopes on the fly for atmospheric flux, at a small scale to record petroglyphs, on a desktop to build 3-d models of artifacts, underwater for close up work (not the doggerland mapping referred to above but, say, recording a drowned roman wall or a shipwreck -- lidar can only penetate a meter or two except in extremey clear water). Anyway, it's quite the tool and for archaeological purposes, I think we will see a huge increase of off-the-shelf purchasable map sheets as the future direction. Governments will scan their entire countries for resource management purposes - in BC, the whole NE sector has been preemptively flown, Alaska has done thousands of square km of their National Forests, etc.

One classic outcome of this kind of work has been the identification of a previously unknown fault near Seattle, on Bainbridge Island. Forewarned is forearmed!

For forestry here in BC, it has been revolutionary. The lidar data on the one hand provides accurate forest canopy images in 3-D, allowing species composition and age to be determined (basically putting timber cruisers out of work). On the other hand, the derived "bare earth model" allows for accurate and (hopefully, environmentally-appropriate) road building and forestry logistics. I'd still rather they horse-logged, but no question that Lidar is enabling better forestry practices in the always contentious BC industry.
posted by Rumple at 10:16 AM on July 30, 2012 [1 favorite]

Wow, that could be an FPP all by itself, homunculus! Or at least it's a subject deserving of one. Don't know if there's much out there online.

Kevin, it's fascinating, but it didn't seem like there was quite enough for a good FPP at the time, so I figured I'd wait until I found more (or someone else posted about it.) There was an exhibit with a blog, btw. If you or anyone else wants to make a FPP about Doggerland, go for it.
posted by homunculus at 12:29 PM on July 30, 2012

You had me at "flying lasers." But the rest is also cool.
posted by Halloween Jack at 5:54 PM on July 30, 2012

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