[Robotgroup] Triangulation using a Rich Skyline Telescope

[brooksdesign]

I've seen several differant versions of what I think you are suggesting as not so much a phase timing approach but instead a image recognition.My friend and bandmate James McCartney of LiQuiD MicE and the UT astro dept. wrote a starfinder program for the Hubble Space Telescope that work so much better than the one NASA paid a subcontractor mega bucks for,everyone started using it instead, so the sub tried to sue him.If I remember correctly he released it as freeware and UT's lawers backed him up on it. I forwarded this to him and hope to get his input soon.
  I've also seen something like this in a digital pen and paper combo where each sheet of this special paper has a random dot pattern that a tiny camera on the pen can navigate and map into a bitmap or jpeg or something like that then convert to wordpad or something else like that.
  And yet another type is the projected pattern for a version of 3d mapping used in a telepresence system.
-brooks

-----Original Message-----
>From: Bruce Waters <biwaters at austin.rr.com>
>Sent: Feb 2, 2008 8:05 AM
>To: robotgroup at puremagic.com
>Subject: [Robotgroup] Triangulation using a Rich Skyline Telescope
>
>I agree with others who have mentioned the difficulty
>of achieving the accuracy (centimeters) at the costs
>allowed using classical RF triangulation.   If you are
>willing to consider a rather dramatic modification of 
>the beacons, you might find meeting those specs more 
>realistic.   My approach would be to use a large number 
>of led's (eg. Christmas light strings) nonuniformly 
>arranged around the boundary(or elsewhere) to provide 
>a high angular resolution "skyline".   To reduce
>ambiguity it is important to insure that the interlight
>spacing not be excessively uniform.
>
>I would use a cheap telescope (with a right/left pair of 
>light edge sensors at the focus) at the same height as the 
>led's.  I would sweep or rotate the telescope.  I would 
>train the robot on the spacing of the led's from some 
>known near-central point.   I would move the robot 
>directly at some specific led beacon(a non-rotating 
>second telescope might facilitate this) and develop a 
>mathematical (initially tabular, then add sophistication) 
>model of the variations in angles to the rest of the 
>skyline.     I would return to the central point and pick 
>some number of additional headings to train the bot.  
>Consider mounting the telescope low and using 
>software techniques to ignore the wheels.
>
>Learning the skyline allows very low precision(just 
>string chunks of it around the boundary) initial
>placement the skyline.  It allows software 
>improvements to accuracy and data volume 
>requirements.  It provides an angular resolution 
>related to the telescope power and the number of 
>led's in the skyline.   It allows local incremental 
>improvement of the resolution by adding skyline in 
>appropriate places.   It is an interesting continuing 
>project to improve the performance without spending 
>more on hardware.   It can be wonderfully cheap for 
>the performance delivered.
>
>A valuable improvement you should consider is an 
>elevation tracking gimbal mount for the telescope 
>to reduce the exaggerated sensitivity to tilt of the 
>robot and vertical variations in the skyline as the 
>telescope rotates.   The light sensor for this 
>improvement should be upgraded to at least 
>four quadrant and could go (fast, low res)
>video.  Note that the skyline does not have to be 
>continuous but that precision does require that 
>adjacent beacons be visible at angles that are not 
>too acute in several major compass headings.
>
>Just like radio beacons, chance light sources in the
>skyline may be used as beacons in some cases so
>your robot may function adequately in some
>environments without additional beacons.  The
>elevation control and perhaps a zoom control
>on the telescope can greatly enhance such 
>serendipitous operation.   The flexibility and
>adaptability of this approach is outstanding.
>It is a wonderful platform to explore fuzzy
>logic, data volume reduction techniques, and 
>high reliability software concepts.
>
>Bruce Waters
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