function dist=sphdist(lat1,lon1,lat2,lon2,radius)
%% SPHDIST distance between two points given by lat and lon
%
%  sphdist calculates the distance between two points given by
%  latitude and longitude coordinates, assuming a perfect sphere
%  with a given radius
%
%  input: lat1:  latitude of point #1 in degrees
%         lon1:  longitude of point #1 in degrees
%         lat2:  latitude of point #2 in degrees
%         lon2:  longitude of point #2 in degrees
%         radius: radius of the sphere
%
%  output dist: distance between point #1 and #2 [m]
%
% Created by Patrick Eriksson
% Date: 2010-01-23

deg2rad = pi/180.;
ga = (lon1-lon2).*deg2rad;
a = (90.-lat2).*deg2rad;
b = (90.-lat1).*deg2rad;
c = acos(cos(a).*cos(b)+sin(a).*sin(b).*cos(ga));
dist = radius.*c;