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Public Lab Research note


A Flight of Ice and Fireweed

by cfastie | July 13, 2015 22:57 13 Jul 22:57 | #12058 | #12058

Above: Fireweed (Epilobium angustifolium) near Glacier Gap Lake in the Amphitheater Mountains in central Alaska.
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Yesterday was a perfect day for half-spherical panoramas near Fairbanks. There were puffy clouds all around so the sky photos would stitch together, and the ground was brightly lit by the sun so it was not much darker than the sky. There was plenty of wind to loft a Saturn V Rig, although it felt marginal at ground level when I chose the Fled kite and took the legs and most bumpers off of the rig to save weight. As soon as the kite reached a few hundred feet it flew steadily.
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The Fled can lift a rig in a little less wind than a nine foot Delta. It is very good at floating when the wind slackens so the rig does not descend too much. Photo by Galen.
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The KAP location was an apparently boring hay field near a cabin I had rented during graduate school. It was an easy place for a quick flight, but I remembered that I had seen patterned ground nearby when my landlord took me up in his Cessna for a short tour (he kept his plane in a shed next to my cabin). I did not remember where the patterned ground was, and I never found it during the KAP session. But it was beautifully revealed in the photos from the Saturn V Rig.
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The polygonal pattern in the field of fireweed is a network of shallow trenches formed when ice wedges thawed. In the distance are some small thermokarst ponds.
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Patterned ground is a common feature in the arctic. Ice wedge polygons are formed when very cold soil contracts and forms cracks at the surface, similar to mud cracks in drying lake beds. When water fills the cracks, ice wedges form and grow. It has to be really cold for ice wedge polygons to form so they are not very common at low elevation south of the arctic. There are just a few active examples visible near Fairbanks (which is 115 miles south of the arctic circle) but the area of our flight probably has many acres of active ice wedges under forest.
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It was a warm breezy afternoon and the KAPing was easy while the thunder clouds slid past on either side of us. The Saturn V Rig went up with only two pieces of tubing for camera protection and no legs. Photos by Galen.
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There are some ponds at the edges of the hay fields where I launched the kite, and I assumed these were formed when the forest was removed and ice masses thawed (the ponds were probably not there when the land was cleared for agriculture). I could not see anything that looked like patterned ground, but when I saw an abandoned hay field covered in blooming fireweed, I decided that it might make a colorful KAP subject. I was greatly pleased to see obvious polygons in the pink field when I viewed the aerial photos later.
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Now that I know where these ice wedge polygons are I will explore them up close the next time I visit.

After the fireweed field was cleared of trees decades ago it was used as a hayfield for a while before it was abandoned. So I assume the ice wedges started to thaw and made it impossible to drive farm equipment around. Decades later the depressions made by the thawing wedges are conspicuous. It would be good to explore the intact forest adjacent to the patterned field to see if the pattern is present there. I also wonder whether the polygon borders are wetter than the centers. Of course they won’t be for long, because winter is coming.


This is the truly spherical version of the panorama in which you can look at the zenith and the nadir. The top of the sky was filled in using Photoshop.

There are a few beta test units of the Saturn V Rig and assembled SkyShield autoKAP controller for sale at the KAPtery. In a week or two there might also be kits available of the full release version of the SkyShield (v. 2.3). The first kits of SkyShield 2.3 are reserved for the current beta testers who have posted research notes about their experiences. These will be heavily discounted, especially for those (Pat) who have provided lots of feedback (limited time offer, so get posting!).

Flight notes:

Camera:

  • Model: PowerShot S100
  • ISO: 125
  • Shutter speed: 1/800 second (Tv)
  • Focus: manual on infinity
  • Focal length: 24mm (eq.)

SkyShield:

  • Version: 2.0 (4-switch DIP)
  • Sketch: version 2.05
  • Mode: Mode 0 (slower version of mode with 4 tilt angles, 8 pan positions at and above the horizon, 6 below the horizon, and 3 at nadir, 25 photos per cycle)
  • Customization: The nadir tilt angle was changed from 20 to 11 so the camera was pointed straight down. The uppermost tilt angle was changed from 127 to 124 because otherwise the Picavet cross was included in some photos.

Flight:

  • Kite: Fled
  • Duration: 57 minutes
  • Photos taken: 1111

Panorama stitching:

  • Software: Microsoft ICE
  • Post processing: No adjustments were made to any photos before stitching.
  • I tried about five different sets of 25 photos (one full pan/tilt cycle) before ICE made a panorama with only minor stitching errors.
  • The original embedded panorama from Photosynth has been replaced with one from 360Cities.net because Photosynth no longer exists.

2 Comments

Hey Chris,

What is your process for creating panoramas in ICE? Which projection do you use?

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For 360° kite panoramas, I let ICE analyze the photos and do the stitching. If the stitching works, ICE usually selects the "spherical" projection to display the result. That projection is usually what you want for a (mostly) spherical panorama. Then you can straighten the horizon (a key step) and center the panorama by dragging it around before you export it. Skip the cropping step if you want to display it in a spherical viewer.

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