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Doc Edward Morbius ⭕ · @dredmorbius

2071 followers · 14640 posts · Server toot.cat

Community Health Maps - How Accurate is the GPS on my Smart Phone? (Part 2)

44 bits

So, a redditor tracked down the location of a monolith placed in the Utah desert a few years ago, recently discovered by authorities, who did not disclose where it was.[1]

It's relatively well known that 33 distinct bits is enough to uniquely identify any individual person now alive on Earth.[2]

Geospatially, assuming 10m² resolution, 44 bits is enough to identify any unique region on Earth's land surface (46 bits buys you the oceans).

Searching for a ~1m² monolith visually within a 10m² square is reasonable.

GNU units:

You have: ln((.3 * 4 * (earthradius^2) * pi)/10m^2)/ln(2)
        Definition: 43.798784
You have: ln((1 * 4 * (earthradius^2) * pi)/10m^2)/ln(2)
        Definition: 45.535749

49 bits buys 1m accuracy, 63 1cm, 69 1mm. Anywhere on Earth, land or sea.

For comparison, cellphone positioning accuracy is typically 8--600m:

3G iPhone w/ A-GPS ~ 8 meters
3G iPhone w/ wifi ~ 74 meters
3G iPhone w/ Cellular positioning ~ 600 meters

https://communityhealthmaps.nlm.nih.gov/2014/07/07/how-accurate-is-the-gps-on-my-smart-phone-part-2/

https://www.gps.gov/systems/gps/performance/accuracy/

The power of disparate data traces to rapidly narrow down search spaces on a specific item, individual, or location, is what makes #BigData aggreggation so powerful, and terrifying.