> On Aug 17, 2018, at 12:59 PM, tom <[email protected]> wrote:
>
> hi,
>
> i have a Task model with and address plus radius in miles (adress is being
> translated to lat/lng via geo-api-call).
>
> Now i have a person at location x and i want to know if that person is within
> that circle of the TaskModel's location plus radius.
>
>
> does anyone know how to calculate that w/o using geo-api calls?
>
>
> thx
> tom
That's called the great-circle distance. It's not overly complex to implement
by hand (I've done it in SQL and in app code in the past):
https://en.wikipedia.org/wiki/Great-circle_distance
You might need to be careful about using floats, as they aren't perfectly
accurate (funny rounding stuff can happen which could cause exceptions). Maybe
use BigDecimal if doing your calculation with your own ruby code.
Hope that helps.
Phil
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