GIS::Distance::Vincenty 0.01001

GIS::Distance::Vincenty Perl module contains Thaddeus Vincenty distance calculations. SYNOPSIS my $calc = GIS::Distance::Vincenty->new(); my $distance = $calc->distance( $lon1, $lat1 => $lon2, $lat2 ); For the benefit of the terminally obsessive (as well as the genuinely needy), Thaddeus Vincenty devised formulae for calculating geodesic distances between a pair of latitude/longitude points on the earths surface, using an accurate ellipsoidal model of the earth. Vincentys formula is accurate to within 0.5mm, or 0.000015", on the ellipsoid being used. Calculations based on a spherical model, such as the (much simpler) Haversine, are accurate to around 0.3% (which is still good enough for most purposes, of course). Note: the accuracy quoted by Vincenty applies to the theoretical ellipsoid being used, which will differ (to varying degree) from the real earth geoid. If you happen to be located in Colorado, 2km above msl, distances will be 0.03% greater. In the UK, if you measure the distance from Lands End to John O Groats using WGS-84, it will be 28m - 0.003% - greater than using the Airy ellipsoid, which provides a better fit for the UK. NOTE: This formula is still considered alpha quality in GIS::Distance. It has not been tested enough to be used in production. FORMULA a, b = major & minor semiaxes of the ellipsoid f = flattening (a-b)/a L = lon2 - lon1 u1 = atan((1-f) * tan(lat1)) u2 = atan((1-f) * tan(lat2)) sin_u1 = sin(u1) cos_u1 = cos(u1) sin_u2 = sin(u2) cos_u2 = cos(u2) lambda = L lambda_pi = 2PI while abs(lambda-lambda_pi) > 1e-12 sin_lambda = sin(lambda) cos_lambda = cos(lambda) sin_sigma = sqrt((cos_u2 * sin_lambda) * (cos_u2*sin_lambda) + (cos_u1*sin_u2-sin_u1*cos_u2*cos_lambda) * (cos_u1*sin_u2-sin_u1*cos_u2*cos_lambda)) cos_sigma = sin_u1*sin_u2 + cos_u1*cos_u2*cos_lambda sigma = atan2(sin_sigma, cos_sigma) alpha = asin(cos_u1 * cos_u2 * sin_lambda / sin_sigma) cos_sq_alpha = cos(alpha) * cos(alpha) cos2sigma_m = cos_sigma - 2*sin_u1*sin_u2/cos_sq_alpha cc = f/16*cos_sq_alpha*(4+f*(4-3*cos_sq_alpha)) lambda_pi = lambda lambda = L + (1-cc) * f * sin(alpha) * (sigma + cc*sin_sigma*(cos2sigma_m+cc*cos_sigma*(-1+2*cos2sigma_m*cos2sigma_m))) } usq = cos_sq_alpha*(a*a-b*b)/(b*b); aa = 1 + usq/16384*(4096+usq*(-768+usq*(320-175*usq))) bb = usq/1024 * (256+usq*(-128+usq*(74-47*usq))) delta_sigma = bb*sin_sigma*(cos2sigma_m+bb/4*(cos_sigma*(-1+2*cos2sigma_m*cos2sigma_m)- bb/6*cos2sigma_m*(-3+4*sin_sigma*sin_sigma)*(-3+4*cos2sigma_m*cos2sigma_m))) c = b*aa*(sigma-delta_sigma).

Requirements:	No special requirements
Platforms:	Linux
Keyword:	Cos,  Gis,  Gisdistancevincenty,  Lambda,  Libraries,  Perl Module,  Programming,  Sigma,  Sin,  Thaddeus Vincenty,  Vincenty Perl
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