Public Lab Research note

Balloon mapping meetup, Saturday 1/12/13, in San Francisco

by patcoyle | January 21, 2013 18:42 21 Jan 18:42 | #5664 | #5664

Balloon mapping meetup, Saturday 1/12/13, in San Francisco: Stewart Long posted, Hello, we are getting together to make a map this Saturday. The initial plan is to meet at Fort Mason Green and map around the waterfront at 9. Meeting early to hopefully have low winds. Discuss further at the Public Lab NorCal list. Stewart went with 9AM because the winds are likely to be calmer, and the Niners playoff game is going on after lunch so it's good to be out in front of that.

In response to questions about how long the session would take, Stewart indicated usually 1-3 hours, but we will find out as we go with the group. We will determine together where to walk around and map. It should be easy to find us if anyone wants to come later (look for the red balloon in the air). He also suggested people bring sunglasses, though it may not be sunny it's nice to have shades to look at the balloon. Also, if anyone wants to bring any kind of gear to try please do.

Stoney and Ben shared a car ride up from the South Bay, Mountain View, Sunnyvale area. Several others came from San Francisco and other parts of the Bay Area.

Pat brought 219 scf of helium (big tank), Delta and Sutton FF kites, two pairs of CHDK triggered vis/IR cameras (A490/495s and A1200s) and Al frame with picavet for two cameras, two grassroots mapping kit balloons, gps tracker, juice bottle rig for single camera, etc.

We filled the balloon, but when attached rig, didn't have enough lift. Since Pat had flown same set-up successfully at Cal Poly EWB event, we added more helium and on second try had plenty of lift. However, we discussed the weight of the rig and that it is clearly not optimized. As images in the photo gallery show, as flown the total weight was about 1200 grams, within accuracy of food scale.

We started with Pat's A1200 pair shooting visible and IR via iPhone triggered CHDK usb remote circuit. We brought the balloon down and changed cameras twice after initial launch.

Image gallery image shows track and altitude profile. The details of the gps track from the iPhone app GPS-Trk, show maximum elevation of ~174 meters.

First we changed to Bobby's GoPro which we flew for video while taking stills with Alan's SD550 shooting with CHDK intervalometer script. The image gallery shows the Palace of Fine Arts: the team on the ground, the rig aloft and one image from the SD550.

Then, on final segment, we flew Bobby's GoPro for video and Pat's A495 shooting continuously with rubber band over shutter. The clicking sound at altitude, in Bobby's video below, is the A495.

Marina Green and Fort Mason Aerial Balloon Photography from Bobby Sudekum on Vimeo.

Another image gallery image shows track and altitude profile from the QStarz BT-Q1300s, which was on the rig the whole time. The maximum elevation of ~240 meters was in the final segment. We used the PLOTS balloon mapping kit spool with 1000 feet of line, and had almost all of it out.

Ground-based videos are in playlist and below:

Noticed some glitches. For the dual camera flight, the synch was not correct, appeared that one was triggering an interval off, nominally 4 seconds - so it matters; auto registration/processing with Ned Horner Image-J tool will be problematic. We are looking into the issue and have good suggestions to try from the CHDK forum people.

Additional indignity, is one of the Al frame legs was slightly visible in the A1200 visible images so images needed to be cropped. Need more care in checking that camera field of view is clear prior to launch.

The A495 images in continuous mode were good, but pretty oblique at the end of the flight due to tilting of the rig.

Map of few images from first segment and below:

IR image map i and below:

The Mapknitter experimental mutispectral export produced a nice NRG map.

The last flight segment with the A495 continuous images covered such a large extent that the full map was too big to export from Mapknitter. The first part of it can be viewed, but not exported. Sub-map of the last part and below:

Other maps are coming as well. Stewart is preparing a large map in PhotoShop.

Sure was a great day for the session.


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