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This is a more accurate analysis than before.
8 char geohashes are noticeably less precise than GPS point-distance calculations - but probably good enough for MVP1
A radius of 20m to identify “nearby” geohashes for matching is excessive - a 10m radius gives better results.
The use of 8 char geohashes + notifying only when 4 of 6 points are detected, more-or-less masks the GPS inaccuracy that we are seeing (at least for my measurements in rural Italy). It looks as though improvng GPS accuracy in MVP1 (SAF-175) may not in fact be necessary for MVP1.
GPS Reliability (SA-278 / SAF-257), however, remains absolutley critical.
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