Hello all, I am writing a program/game where you can move on a sphere's surface (like you are walking the earth). So I want to tell my object "move 10 meters in that direction", with a velocity-vector. The z-coordinate will never be used so I can construct this vector as: vx = speed * cos(angle) vy = speed * sin(angle) vz = 0 The object is placed on the sphere with: x = radius * cos(lat) * cos(lon) y = radius * cos(lat) * sin(lon) z = radius * sin(lat) Now I want to know the new coordinates (cartesian or spherical) after the object has moved. I've been aware of the formula's in the attached image. But i don't quite know how to use them. Thanks in advance.