I was just about to tell you what the problem was! ;-) Bob S
> On Jan 31, 2015, at 12:42 , Michael Doub <miked...@gmail.com> wrote: > > Of coarse it was me. And as you would expect, I found it right after sending > the mail to the list. > > put lon2 - lon2 into dlon should be put lon2 - lon1 into dlon > > Sorry for the junk mail. > > -= Mike > > > > On 1/31/15 3:33 PM, Michael Doub wrote: >> I am trying to covert the javascript that computes distance based on >> longitude and latitude from this page: >> http://andrew.hedges.name/experiments/haversine/. >> >> The sites javascript is returning 0.341 miles and 0.549 km >> Livecode is returning 0.097 miles and 0.157 >> >> I have been staring at this for a while. Does anyone see my mistake or is >> there a precision issue tripping me up? >> >> Thanks >> Mike >> >> >> >> on doit >> answer __latLongDist (38.898556, -77.037852, 38.897147, -77.043934) >> end doit >> >> >> function __latLongDist t1, n1, t2, n2 , mk >> put 3961 into Rm -- mean radius of the earth (miles) at 39 degrees from >> the equator >> put 6373 into Rk -- mean radius of the earth (km) at 39 degrees from the >> equator >> put t1 * pi/180 into lat1 -- convert degrees to radians >> put n1 * pi/180 into lon1 >> put t2 * pi/180 into lat2 >> put n2 * pi/180 into lon2 >> put lat2 - lat1 into dlat >> put lon2 - lon2 into dlon >> put (sin(dlat/2))^2 + cos(lat1) * cos(lat2) * (sin(dlon/2))^2 into aa >> put 2 * atan2( sqrt(aa), sqrt(1-aa) ) into cc >> put cc * Rm into Dm >> put cc * Rk into Dk >> return round (Dm,3), round(Dk,3) >> end __latLongDist >> >> >> >> /* main function */ >> function findDistance(frm) { >> var t1, n1, t2, n2, lat1, lon1, lat2, lon2, dlat, dlon, a, c, dm, dk, >> mi, km; >> >> // get values for lat1, lon1, lat2, and lon2 >> t1 = frm.lat1.value; >> n1 = frm.lon1.value; >> t2 = frm.lat2.value; >> n2 = frm.lon2.value; >> >> // convert coordinates to radians >> lat1 = deg2rad(t1); >> lon1 = deg2rad(n1); >> lat2 = deg2rad(t2); >> lon2 = deg2rad(n2); >> >> // find the differences between the coordinates >> dlat = lat2 - lat1; >> dlon = lon2 - lon1; >> >> // here's the heavy lifting >> a = Math.pow(Math.sin(dlat/2),2) + Math.cos(lat1) * Math.cos(lat2) * >> Math.pow(Math.sin(dlon/2),2); >> c = 2 * Math.atan2(Math.sqrt(a),Math.sqrt(1-a)); // great circle >> distance in radians >> dm = c * Rm; // great circle distance in miles >> dk = c * Rk; // great circle distance in km >> >> // round the results down to the nearest 1/1000 >> mi = round(dm); >> km = round(dk); >> >> // display the result >> frm.mi.value = mi; >> frm.km.value = km; >> } > > _______________________________________________ > use-livecode mailing list > use-livecode@lists.runrev.com > Please visit this url to subscribe, unsubscribe and manage your subscription > preferences: > http://lists.runrev.com/mailman/listinfo/use-livecode _______________________________________________ use-livecode mailing list use-livecode@lists.runrev.com Please visit this url to subscribe, unsubscribe and manage your subscription preferences: http://lists.runrev.com/mailman/listinfo/use-livecode
