Friday, July 07, 2006

Project Iteration II: Object pattern matching. Sort of.

So, from my first post, we all know our imaginary sector of the university. Now let's imagine we thought about the measurements we take differently. Instead of randomly taking readings here and there, and then working out distance and then signal estimates, let's think with a little more forethought. Perhaps, just perhaps, we could look at points of this sector where a particular transition occurs. Like a signal passing through a wall, or a tree, or around a corner. With this in mind, we can take less readings, and simply reapply the logic for each situation it occurs in in the future- passing through a wall should give a common decrease in signal, shouldn't it?

With this in mind:
Seems a great idea, doesn't it? Means we don't have to take a bucketload of readings, right? Well, let's have a look:
As we can see, we've hit a snag. Rather, we've hit several:
  • We know what signal strength is decreased by when it passes through walls, but we don't actually know what it is at the wall itself. This alone isn't such a big issue- after all, who is going to use their laptop in a wall? (Go on then, prove me wrong.)
  • The biggest issue here is the bottom right hand area, which has an abundance of "?"s, which represent an unknown signal strength. Why? Well, there's a few things here. The first is a matter of precedence. We know that supposedly signal decreases by one over each square it travels in air (6-5-4), but what happens when we get to the corners of the building at (3,4)? Note here we have readings of 8, 8, 8, 7 and 5 around it. Which of these do we minus one from? Further more, look at (5,8). The first thing we think is, "ah- this will be 7, it's one square away from 8". But wait, it's behind a tree, so do we apply the "minus whatever when we go through a tree" rule? Indeed, what does "through a tree" mean? Does it have to be north-to-south as measured originally?
All of a sudden, this approach has become very messy. Perhaps, we could adapt an approach that aggregates the surrounding squares, giving us our answer. We will explore an approach like this in Iteration three (keep in mind my project iterations won't neccessarily follow this order, or even feature some of these ideas, I'm just throwing some ideas against a wall and seeing what bounces). For the time being, I like the approach presented here- but it needs to be replicated more. I need more than one reading for "through a tree", and I need to cover other situations like "round a corner" to be sure of full coverage. I also need to work out this problem of precedence. Even so, it's a start.

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