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I've always wondered how "segment matching" algorithm works

Is it just brute force checking every gps lat/long point in an activity to see if any path numbers are "close" to any segment lat/long start point? And then if so, to additionally match an end-point, and then if so see how many points inbetween match?

Seems like a heck of a db query, math ranges? Are the gps point normalized somehow to accelerate the process or just stored as original floating point and let the db engine do the heavy work?

adding: oooh it's right in the patent, figure 9+



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