From 2dfdc09969b8c32887cb45b6f7ff286227ddfd27 Mon Sep 17 00:00:00 2001 From: Johannes Hofmann Date: Wed, 28 May 2008 19:18:53 +0200 Subject: use numerical more stable distance formula --- src/Panorama.cxx | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/src/Panorama.cxx b/src/Panorama.cxx index 32e14f4..8bab3e4 100644 --- a/src/Panorama.cxx +++ b/src/Panorama.cxx @@ -413,8 +413,11 @@ Panorama::update_coordinates() { double Panorama::distance(double phi, double lam) { - return acos(sin(view_phi) * sin(phi) + - cos(view_phi) * cos(phi) * cos(view_lam - lam)); + double d_lam = view_lam - lam; + + return atan2(sqrt(pow(cos(phi) * sin(d_lam), 2.0) + + pow(cos(view_phi) * sin(phi) - sin(view_phi) * cos(phi) * cos(d_lam), 2.0)), + sin(view_phi) * sin(phi) + cos(view_phi) * cos(phi) * cos(d_lam)); } double @@ -428,7 +431,6 @@ Panorama::alpha(const Hill *m) { return fmod(atan2(sin_alph, cos_alph) + 2.0 * pi_d, 2.0 * pi_d); } - double Panorama::nick(const Hill *m) { double b, c; -- cgit v1.2.3