Yesterday we went to the beach for a second practice session with the beepers. After seeing the multiple burial instructions in this video I was keen to have a go searching for more than one transceiver. The initial stage of the multiple burial search is the same as if you’re looking for a single signal, so the practcie was useful for that situation too.
With the BCA Tracker there are two (there might be more?) methods of dealing with multiple signals. The first, which is what I was practicing and is general to all trasceivers, is called the three circle method; with the Track the searcher only uses the regular search (SE) mode. The second and more advanced method described, specific to the Tracker, makes use the transceiver’s special (SP) mode.
This is my understanding of the 3 circle method. Once you’ve found the first signal, assuming you can’t turn it off (perhaps because others are still probing/digging), you travel in a circle around the signal looking for a lower distance reading and/or listening for another audio beep. That first circle is three steps out from the lowest distance reading of the original find.
If you don’t pick anything up on the first pass you take another three steps back and walk a second circle. Again, if nothing is found you perform a third circle, three steps back from the second. If you still don’t find anything you go back to the point at which you left your orginal primary search (when you first detected a signal).
I think the theory is pretty simple. If there’s another signal close by, at some point on one of the three circles you’ll be closer to it, than the original beacon. This methodical approach seems to be a reliable way of seperating the two signals.
Check out my first attempt; apologies for the cheesy intro…
In this example I located the second signal on the first of the three circles. Note that first time the beeper detected the second signal I was unsuccessful in locking onto it. After returning to the circle it only took a couple more steps before the signal was detected again, this time the dropping distance was conclusive.
And here’s my second attempt.
Here are some comments:
Picking up the second signal. In the first case where the signals were closer together, the search was quicker. This may seem obvious, but my orignal expectation was that in cases where signals are close together, they’d be harder to separate. The Tracker easily picks them out when rotated side-to-side.
In the second example it took longer to pick up the other signal. Quite a few times, each in the same area, I stopped to check or tried following a different signal only to turn back to walking the circle. In these cases I was fairly certain that the other beacon was over there, but the data I was getting didn’t seem conclusive
Was I walking too fast? Should I have followed my instincts or kept using the circles? I guess more practice would answer some of these questions. Either way, I did end up clearly detecting a much lower signal, and it led right to the beacon.
Audio vs. video. At the time I was definitely paying more attention to the distance read out than the audio beeps. However, after watching the video back it’s clear that the beeps are also very informative.
My original approach. Again, something that I didn’t think about at the time was the direction of my approach to the first beacon. This should give a clue as to where the other signal is less likely to be.
Nothing found after three circles? If you don’t find anything you need to return to the original primary search and continue searching the rest of the deposition area. In this case I’m not sure how you would ignore the first signal if it still wasn’t turned off. It seems like it would be in the way…
Overall times. These were my first two attempts at finding two signals. The first search took around 4 minutes and second around 6 minutes. Considering that I was learning the search procedure, I think this is another indication that the BCA Tracker is an easy unit to operate.