[meteorite-list] Wales image analysis
From: Charles R. Viau <cviau_at_meteoritecentral.com>
Date: Thu Apr 22 10:28:22 2004 Message-ID: <008401c38b14$50951460$1800a8c0_at_chupa> Excellent analysis!. Do you have a ballpark altitude of the head? do you think it may have been > 6 km ? Thanks CharlyV -----Original Message----- From: meteorite-list-admin_at_meteoritecentral.com [mailto:meteorite-list-admin_at_meteoritecentral.com] On Behalf Of Matson, Robert Sent: Sunday, October 05, 2003 3:25 AM To: 'meteorite-list_at_meteoritecentral.com ' Subject: [meteorite-list] Wales image analysis Hi All, Okay, I've spent quite a few hours playing around with trajectory solutions based on the two images (the original higher-zoom image taken from Pencoed and the second wide-field shot taken from Porthcawl). While it would be nice to have the exact coordinates of the two observers, and some info on the fields of view of the two images, the "flavor" of the solutions is not likely to change that much. And this is where it gets interesting because those solutions do NOT point to an object in level flight. In other words, the rules of geometry are forcing me to reverse my position and join the pro-bolide club! Here's why. The wide field image from Porthcawl has the sun in the field of view which allows one to place some reasonable bounds on both the FOV of the image and the azimuths and elevations of the trajectory. The track, if projected to the horizon, would intersect somewhere in the azimuth 230-240 range. (At 6:15pm BST, the sun was at elevation 7.8 degrees, azimuth 259.5 as viewed from Porthcawl.) If someone has a more accurate estimate of the time of the image, please let me know - the only reference I've seen is around 6 pm. Now Pencoed is actually located ENE of Porthcawl (I'm using a location 13.4 km east and 3.6 km north in my model). What this means is that the sight lines to the contrail are very similar from the two locations, and this is a problem. You see, a constant-altitude contrail under these circumstances would have to appear more steeply inclined relative to the horizon as seen from Pencoed, and instead the contrail is, if anything, slightly less inclined in the 15-year-old's image. (By the way, the Pencoed image is not level w.r.t. the horizon; the image needs to be rotated about 7 degrees clockwise to align it with the Porthcawl image. But even after correcting for this rotation, the Porthcawl slope is still greater than that in the Pencoed image.) I've tried a variety of reasonable values for the field of view of the wide-field image, which in turn drives the time of the exposure, the azimuth/elevation of the sun and the azimuth and elevation ranges of the trajectory. Clouds visible in both images can be used to determine corresponding azimuths and elevations in the zoomed-in image. The result is always the same: a steep, high altitude trajectory. If someone can get an accurate time for the Porthcawl image, and good coordinates for the two observers, I'll be happy to compute a best fit triangulation solution. Perhaps DoD will have a track on this object after all -- time will tell. Cheers, Rob ______________________________________________ Meteorite-list mailing list Meteorite-list_at_meteoritecentral.com http://www.pairlist.net/mailman/listinfo/meteorite-list Received on Sun 05 Oct 2003 03:43:00 AM PDT |
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