Going north means changing latitude to approach 90 degrees north latitude at the pole. Those degrees of latitude are evenly spaced in distance (s=rtheta, if theta is angle north of the equator).

Going east means changing longitude, rising from -180 degrees to 180 and then resetting. Those degrees of longitude correspond to less and less distance at the poles (s=rcos(theta)*phi, if theta is angle north of the equator and phi is angle around the axis).