On Jun 3, 2:12 pm, Marty <[email protected]> wrote: > Hi, > > I would like to draw a static map and use a polyline to conect 2 > points. > > This is straight foward and rather easy to acomplish, my challenge is > having the polyline follow the Great Circle path on the map instead of > a straight line. > > Any ideas? > > Thanx in advance
formula by Ed Williams Aviation Formulary V1.43 http://williams.best.vwh.net/avform.htm#Dist ===================================== Intermediate points on a great circle In previous sections we have found intermediate points on a great circle given either the crossing latitude or longitude. Here we find points (lat,lon) a given fraction of the distance (d) between them. Suppose the starting point is (lat1,lon1) and the final point (lat2,lon2) and we want the point a fraction f along the great circle route. f=0 is point 1. f=1 is point 2. The two points cannot be antipodal ( i.e. lat1+lat2=0 and abs(lon1-lon2)=pi) because then the route is undefined. The intermediate latitude and longitude is then given by: A=sin((1-f)*d)/sin(d) B=sin(f*d)/sin(d) x = A*cos(lat1)*cos(lon1) + B*cos(lat2)*cos(lon2) y = A*cos(lat1)*sin(lon1) + B*cos(lat2)*sin(lon2) z = A*sin(lat1) + B*sin(lat2) lat=atan2(z,sqrt(x^2+y^2)) lon=atan2(y,x) ======================= Distance between points The great circle distance d between two points with coordinates {lat1,lon1} and {lat2,lon2} is given by: d=acos(sin(lat1)*sin(lat2)+cos(lat1)*cos(lat2)*cos(lon1-lon2)) A mathematically equivalent formula, which is less subject to rounding error for short distances is: d=2*asin(sqrt((sin((lat1-lat2)/2))^2 + cos(lat1)*cos(lat2)*(sin((lon1-lon2)/2))^2)) ====================== -- You received this message because you are subscribed to the Google Groups "Google Maps API" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/google-maps-api?hl=en.
