Here is a schematic view of the GPS occultation process. The rapid motion of the low orbiting receiver dominates the changing geometry and largely determines the duration of the occultation — typically about one minute. The much higher GPS satellites move relatively slowly and can be regarded as almost stationary during the occultation. For that reason, most occultations occur in the forward or backward direction with respect to the receiver's line of motion, with relatively few occurring off to the sides.