On 3/26/14, 8:22 AM, Adrian Custer wrote:
are in Montevideo, even in the city center, at the end of the process,
but that is information that we tend know without asking our phones for
help.
You may know you are in Montevideo, but your phone doesn't. :) Even
city-level precision will allow your phone to give you appropriate
weather forecasts or restaurant suggestions.
I'm not an expert at all, and I don't know the app either, but I think
we know the signal strength, right? Maybe the app is recording this as
well, and we're removing the station with too weak signal?
The issue is that we are not *measuring* the wifi signal at every time
step. Instead, the system accumulates wifi signals as they are broadcast
into a set of current signals and uses that store to answer API queries.
So you are getting the 'signal strength of the last received broadcast'.
According to the literature and our experience, WiFi signal strength is
a very poor predictor of distance. When we have a larger number of WiFi
samples, we plan to use a grid-based "voting" algorithm instead of
trilateration.
chris
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