The following figures and formulas have been prepared for determining the maximum allowable heights of objects within the airport’s vicinity. The formulas are used in conjunction with the figure; whereas a formula is assigned a number, that formula corresponds with a point location of the same number on the figure. By using the formula and following the steps outlined below, the maximum allowable height at a point location can be determined.

1. Locate the point (object) in question on the figure (sample point locations identified by numbers are given in various coded airport zones).
2. Apply the formula having the same number as the chosen point location to calculate the maximum allowable height for an object at that point (some formulas will have letter variables A, B, C, etc., which are shown on the figure in Appendix 27-13A).