Re: GPS positions

On 2010-05-22, Mike Ellsworth <younicycle(at)gmail(dot)com> wrote:
> If you don't want to work with postgis, I think you could just use a bit of sqrt
> using double precision - for a circle anyway.
>
> I did something similar for a simple target archery scoring example I
> set up awhile ago.
> http://www.younicycle.com/web/younicycle_com/xml-hr/ex_12_a.html
>
> Many of the other links off this page require login/privileges - but I
> believe this specific page works.
> round(GREATEST(10.5 - sqrt((("xyarchery"."xx" - 200) ^ 2) +
> (("xyarchery"."yy" - 200) ^ 2)) / 20, 0))
> where pixels are being recorded & scored.

you can't apply pythagoras's theorem to latt0tude,longitude
coordinates and get a useful result unless the points are near the
equator.

By far the easiest solution is to us a package, like postgis, that was
prepared by persons who know what they are doing.

the same goes time arithmetic, where leap-years are just one of the
pitfalls.