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Our Members: Joe Poulton—Mapping Geology with High-Resolution Photography [Part 2]

Posted on: May 8th, 2012 by Abbey Smith

Telling the stories of our members is important to us because it helps the community understand who makes up that community.  Member Joe Poulton, with AAC Friend Abbey Smith, produced this stunningly-cool three part series about his experiences in Yosemite—photographing geology in ways that help YOSAR study rockfall, help climate scientists predict change, and a whole lot more…

Photo by Peter Duke

A Personal Experience with Gigapixel Imagery [Part 2]

[Continued from Part 1]…The next day we all converged in the campground where we were given our groups for the shoot. Then we had a gear meeting with instruction on the use of the Gigapan and the Canon G9.  It was amazing how many people were involved. As I got to know people around the camp, everyone had something to do with the Hollywood/LA/ International Film industry. In my group, Franklin Londin was a 3D specialist. Franklin shot every one of his pictures in 3D with this interesting little camera he put together that had two separate lenses and his business card was printed on a pair of 3D glasses. Franklin at the time had recently worked on Speed Racer. Tom Kluyskens worked on Spiderman’s graphics. Then there was the Kiwi, he worked on the computer program that directed the battle scenes in Lord of The Rings: The Two Towers.  Nick Fillingham and his wife rounded out our team. 

Greg Stock, National Park Service (NPS) Geologist for Yosemite also showed up for the gathering. The project was created for his ultimate use in understanding the rockfall and landslide hazard in Yosemite Valley. The end product would be a high resolution photographic Digital Elevation Model (DEM). The large-scale panoramic image would be stitched together by xRez Studios and then laid over a DEM and thrown into a simulated computer environment that Greg Stock can interactively tour with his computer platform. In this way, Greg can visit the specific site of rockfall and landslides as they were before the event to see what signs might have been visible.

Standing around in the campground for the first gathering I was surrounded by people with a lot of graphic and image history. All I had done was take one panoramic image of Mount Hood and a few landscapes. I didn’t believe the situation and how I had become involved with an elite industry group. However, being involved with xRez and this event was a great inspiration to continue down my photographic path.

…Standing around in the campground for the first gathering I was surrounded by people with a lot of graphic and image history. All I had done was take one panoramic image of Mount Hood and a few landscapes. I didn’t believe the situation and how I had become involved with an elite industry group…

After the lesson on equipment use, we took off in our groups to get aquatinted with the gear. My group went to the top of Sentinel Dome. Walking around the southeast edge of this monolithic mound of rock was wonderful; I gave some thought to climbing up this beautiful crack on the southeast side. Common sense out weighed my desire, since I was walking around with an atrophied right ACL and didn’t have all the necessary control of my knee. We continued around to the northeast of the Dome and up to the top.

The landscape rolled away from our perch with greens, grays, and blues dominating the scene. The breeze from the west lapped at our necks. The sun was peering over our shoulders as we gazed north at El Capitan and Half Dome with Yosemite Falls cutting away at the landscape between the giants. Teasing our view to the northeast was Vernal Falls and off in the horizon was the geology of Tuolumne Meadows. All the while the birds were laughing at us. No not really, they were just enjoying the sunshine too.

We got acquainted with our gear taking practice panoramic shots from the Dome. Then we went to explore more of the Park. We enjoyed Vernal Falls, Curry Village, El Cap Meadows and the west tunnel entrance during our tour that day. At the end of the day, as we arrived back in camp, we noticed some destruction had occurred. Joegen Geerds’s tent had been shredded with debris thrown about. After some investigation, we noticed an empty box of tea bags as being the focus. Later that evening the NPS setup a cool looking bear trap near by. The most interesting fact was my bivy bag, which was next to the tent, was untouched.

After that the night’s fire pits burned down to a simmer and the next day beckoned us to begin. We got our gear and headed for our shot location atop the Manure Pile. Yes that’s right, a big pile of rock near the base of El Cap. After some moderate scrambling we reached a large rocky porch for our shoot. We got ready as it neared 1300 hours. The wind had picked up a bit; we started shooting and noticed the wind rocking the Gigapan. We each took turns as wind blockers and stabilizers for the equipment as the robot panned and snapped shots of our landscape section.

Once the hundreds of images were captured we all regrouped back at the campsite to celebrate the success. The next morning I was planning on getting out early to start the drive home. Eric gave me the option of free gear to take—either a GPS or a Lowe Pro camera backpack. Since I know how to use a compass and a map I went for the pack. [Story continues below the gallery...]

I got out of the camp early the next morning, missing the group panoramic and the cool portraits that fellow photog Peter Duke took of members. However, as I drove out that morning I came face to face with a large grizzly that luckily was more afraid of my car, than my car was of that grizzly. Before I could get a photo the bear took off into the dense roadside forest.

After we had all disbanded, xRez Studios first rendered the image by stitching all 10,000 individual images that covered 16 miles of the Valley’s flanks. The render was followed with a large print exhibit in Los Angeles for Siggraph 2008. XRez printed the image on a continuous 40 feet by 5 feet at 300 dpi from a 150,000 pixel render through Maya and Mental Ray software programs. XRez then laid the digital image version over the DEM, which in part was created by a hang glider “equipped with 3 time-lapse cameras which provided a point cloud data representation of the valley walls through use of Microsoft Photosynth.”  Aircraft based laser scanning or Light Detection and Ranging (LiDAR) occurred previously, more on LiDAR after further discussion on the end use of the Yosemite gigapixel image. 

The final image has been a great resource for Greg Stock. Greg has been able to utilize the image for rockfall studies as he stated in an interview recently:

“I have utilized the xRez images in many rockfall studies. Yosemite
Valley experiences about one rockfall per week on average, so since we took
the photos in 2008 there have been ample opportunities to use the photos to
document rockfalls. Examples include rockfalls from Glacier Point in 2008,
near Half Dome in 2009, and near the Royal Arches in 2009-2010. I’ve
attached a paper we published last year on the Glacier Point rockfalls that
give you some sense of how we use the photos.”

In the above mentioned article: High-resolution three-dimensional imaging and analysis of rockfalls in Yosemite Valley, California, there are some impressive notes of modern technology aiding the extensive research being conducted with gigapixel imagery. LiDAR both aerial and terrestrial based efforts that when combined give a more precise volumetric reading than the previous utilized guess work of determining the new rockfall on the talus field below the sheered section of cliff. “Rock-fall volumes have traditionally been estimated using the product of detachment surface areas and an assumed failure depth or thickness; this value can be compared to volume estimates of fresh talus beneath the source area. Both techniques result in large volumetric uncertainties, typically on the order of ±20% and occasionally much larger.”

The terrestrial LiDAR can scan the overhangs and vertical rock faces for proper depth readings successfully, even gaining access to locations that could be hazardous for a person to reach and gain an estimate otherwise. The aerial LiDAR or Airborne Laser scans (ALS) are blind to overhangs and vertical rock faces but are able to “resolve the lower angle topography and upward-facing surfaces” of terrain that the terrestrial efforts can’t determine properly.

The first set of aerial LiDAR was taken in 2006 during the fall. When, “the National Center for Airborne Laser Mapping (NCALM), in collaboration with the National Park Service, collected ALS data for Yosemite Valley and vicinity.” The project in 2006 used “an Optech 1233 ALTM scanner mounted in a turbocharged twin engine Cessna 337. Above–ground-level flying heights varied from less than 100 m to over 2 km, with an average range of 1050 m.”

These two versions of LiDAR combined with the hang glider time lapse create the base for the resulting Digital Elevation Model and helps gain proper mass of what exists at the time of the scan. Then after a rockfall or landslide a new scan is taken and compared to what was there. The LiDAR scans can produce an error in readings of some areas. That is where the gigapixel imagery comes into play. Through this imagery the researchers are able to verify what areas actually fell. This new technology being utilized and combined creates a precision that is remarkable for understanding the changing geology.

The future holds promise too…

Read Part 3 of this 3 part series—and check out some more great photos—on Thursday.

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