A system of three dimensions is used in cargo plans to describe the position of a container aboard the ship. The first coordinate is the "BAY", which starts at the front of the ship and increases aft. The second coordinate is the "ROW". Rows on the starboard side are given odd numbers and those on the port side are given even numbers. The rows nearest the centerline are given low numbers, and the numbers increase for slots further from the centerline. The third coordinate is"TIER", with the first tier at the bottom of the cargo holds, the second tier on top of that, and so forth.