[russell]

Its simple to use dead reckoning to find the vision tetra really (assuming you have dead reckoning equipment on board, and your programmers know how to use it). This method would not be foolproof, and there is a certain percentage of the time that it should not work at all (Im done with math for the day so someone else can figure it out), but it should work most of the time.

Basically you have to insist that you be allowed to position your bot in the left or right slot (not the middle, though you might be able to make it work for that too). Then you use your camera to scan for a vision tetra in front of you, then you determine the heading on which the tetra lies. This is where the problem comes in. It is unlikely that you could get an accurate enough angle to determine where the tetra is if it is not in one of the five tetra positions in front of you, so if both tetras are in the three positions not right in front of you then you just have to take a random guess at which of the other three positions they might be in and go for one. Then based on that angle you determine which position the tetra is in, then use dead reckoning to nail it.

Sorry that explanation was kind of incoherrent, but its the best I can do at this time of night.

Edit: Actually I just studied the field diagram again, and I realised that starting in the center might actually be the best, because you can get reasonably accurate angles on all of the tetras, and the only two that are on aproximately the same heading are the two in front of you, and if there are no tetras anywhere else, then they are both in front of you so you could theoretically be 100% effective. Assuming the pan servo can pan far enough to see the whole field.