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firebase / geofire-js

GeoFire for JavaScript - Realtime location queries with Firebase
MIT License
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Accuracy #13

Closed johnstontrav closed 10 years ago

johnstontrav commented 10 years ago

Hi,

What is the best possible accuracy? Can I get within 500m?

Cheers.

startupandrew commented 10 years ago

You should be able to, though it's less accurate as you get towards the poles, since the earth isnt a perfect sphere.

I'm currently working on a rewrite of this library. Stay tuned...

johnstontrav commented 10 years ago

Hey Andrew,

Great work on v2! Do you know what accuracy we can expect?

jwngr commented 10 years ago

Hey @johnstontrav - GeoFire 2.0 still has the same accuracy problems as you get closer to the poles. It is a tough problem to solve since the Earth is not geometrically consistent. If you are looking for accuracy numbers for things like our SF MUNI demo (https://geofire.firebaseapp.com/sfVehicles/index.html), I can safely say that GeoFire will have a higher accuracy than the GPS readings which generate the data. By this I mean that the algorithm GeoFire uses to find the distance between two latitude-longitude pairs has (in almost all cases - except near the poles) a smaller margin of error than the GPS instrument has in determining the latitude-longitude pairs in the first place. So I wouldn't be too concerned about that kind of thing. If you can explain your use case/worries, maybe I can talk more about it.

johnstontrav commented 10 years ago

thanks for the detail response. I am looking at using GeoFire and Firebase to write a 'people near me' and a 'find my car' app. I was hoping to located people/car within 50 metres or better. Can i get your thoughts? Cheers.

startupandrew commented 10 years ago

Unless those people live on the north pole, GeoFire should work great for this! Sub-50m accuracy should be no problem (and we'll prob do much better -- depending on the GPS you have)

johnstontrav commented 10 years ago

Great news, but I'm going to have to let Santa know he can't have the 'find a sleigh' app.

startupandrew commented 10 years ago

Haha. Darn.