Public Lab Research note


ORD - SFO

by cfastie | October 23, 2013 23:25 | 4,649 views | 3 comments | #9540 | 4,649 views | 3 comments | #9540 23 Oct 23:25

Read more: stable.publiclab.org/n/9540


Last Friday, three of us flew from New England to San Francisco for the Mentor Summit of the Google Summer of Code. Public Lab mentored three students to develop code for three projects, and the three mentors, Jeff Warren, Don Blair, and I attended the two-day summit at the GooglePlex in Mountain View. For some unknown reason, only one of us took an Infragram camera, and I also happened to have window seats all the way there. (I was asked by the mother of a three year old to trade seats so she could sit next to her daughter on the four hour flight from Chicago, but her other seat was over a wing, so I refused. I was roundly scorned by everyone in economy seating, but my responsibility to Public Lab tool testing must always come first.)

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My Infragram camera was a Canon A810 with Rosco 2008 filter, white balanced on blue origami paper under blue sky in the shade. I also had an unmodified Powershot S95. The Infragram images here are either NBG made by swapping the blue and green channels in Photoshop (NIR is displayed in red), or Normalized Difference Vegetation Index (NDVI) made with Ned's Fiji plugin. The photos below are taken between Tonopah, Nevada and Tracy, California in the Central Valley, and are in chronological (east to west) order. All the photos are looking more or less to the north.

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CrescentDunes.jpg
The Crescent Dunes concentrated solar power generator near Tonopah, NV. When completed, 17,000 heliostats will direct sunlight to a 540 foot tall tower where molten salt will be heated to 1050° F. A steam turbine will generate enough electricity to power 75,000 homes. The full diameter (outer ring) is 1.75 miles. This is an RGB image. The Infragram was also nice, but there are not many plants there. One of the eponymous crescent dunes is at lower right.

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CentPivIrr2a.jpg
Center pivot irrigation circles at the Circle L Ranch near Dyer, NV. Both NBG (left) and NDVI (right) highlight where irrigation allows crops to grow. Each circle is 0.5 miles in diameter. Both images are derived from one Infragram photo.

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MonoNDVI2pan.jpg
Mono Lake, CA (in distance) and the eastern ridges of the Sierra Nevada Mountains. The Owens River Valley is at lower right, and Route 395 is at lower left. The hottest NDVI colors are in the foreground because the longer path through air (in the distance) allows blue light to be scattered which increases noise in the blue channel and lowers the difference between red (NIR) and blue values which decreases NDVI values.

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HalfDome.jpg
Yosemite Valley, CA. Half Dome is at center, the main valley bisects the photo right to left. Mount Starr King is in the foreground to right of center.

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YosemiteNBGNDVI.jpg
Yosemite Valley, CA. A similar and slightly wider view than above with NBG (left) and NDVI (right) from an Infragram photo. El Capitan at far left, Granite Flats at far right. The burned area at the edge of the Rim Fire shows up as a dark area under the wing tank in both images.

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CentVall.jpg
California's Central Valley near Tracy, CA. NDVI values fade strongly from bottom to top as scattered light contaminates the blue channel with distance.
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Next up: Photos from the actual Mentor Summit.

Note: Don't worry, the little girl got to sit with her mother after a caring gentleman swapped seats.


3 Comments

You could try to use some of these for calibration using Landsat imagery to estimate NDVI.

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That's a cool idea. I'm sure somewhere in the gradient from near to far the NDVI in these images is correct.

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Amazing! You should rectify the concentrator photo and contact them... i bet they don't have as up to date an image as you took!

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