The Third Dimension:
Because Flying or Swimming creatures can move in all three dimensions, it's often necessary to measure distances between creatures at different angles,or to adjudicate movement upward or downward at an angle.
The Triangulated Distances table shows distances between points at differently heights; the values have been rounded off to the nearest multiple of 5 for convenience in game play. To use the table, find the horizontal distances between the two points and then the vertical distance between them, the point where the column an the row cross is the actual distance. For example, if two creatures are 100 feet apart horizontally and 50 feet apart vertically, the actual distance between them is 110 feet. You can also use the table to determine how far a creature can fly or swim in a turn if it also travels up or down. To do so, find the vertical distance the creature wishes to swim on the left side of the table, then move right until you find the first number that equals the creature's flying or swimming speed.