That's exactly the same as asking "How many different lengths are there on a piece of rope ?" There's no limit to the possible number of different measurements. If you name two different measurements, then no matter how close together they are, I can always name a new one that's in between yours. 'Latitude' on Earth covers a range of 180 degrees, from -90 at the south pole to +90 at the north pole. 'Longitude' covers a range of 360 degrees, being the angle that you can travel in an east or west direction, from the place you start, all the way around the Earth to the place you started from. Just like any other circle.