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12/5/78 AC 150/5300-4B CHG 3 <br />Appendix 7 <br />APPENDIX 7. AIRPORT REFERENCE POINT (ARP) <br />*1. DISCUSSION. <br />a. The airport reference point is used to._geographically locate the a__i_r_- <br />port. It is used for horizontal control only and no elevation is <br />established for the ARP. The location of this point is computed and <br />no weight is given to runway width, thickness, or composition. (A <br />unity runway width is used.) <br />b. <br />To be a meaningful airport reference point, the point must be computed <br />to acknowledge the ultimate runway lengths proposed for development. <br />Closed or abandoned areas should not be included in the computation. <br />The ultimate development is customarily shown on the currently <br />approved airport layout plan. If there is no approved airport layout <br />plan, the areas to be considered are those existing plus those which <br />have been granted airspace approval less those which are to be <br />abandoned. <br />c. The ARP is computed or recomputed as infrequently as possible. The <br />only time that a recomputation is needed is when the proposed <br />ultimate development is changed. <br />2. SAMPLE COMPUTATION. The following procedure may be used to determine <br />the location of the airport reference point. <br />a. Establish two .base lines perpendicular to each other as shown <br />in Figure 1. Let the northerly base line be known as B and the <br />westerly as A. <br />b. Establish the midpoint of each runway. <br />c. Determine the perpendicular distance from the base lines to the <br />midpoints. <br />d. Calculate the moment of areas for each base line as shown in <br />Figure 2. <br />e. Divide each moment of areas by the sum of areas to determine <br />distance of the ARP from each base line. <br />f. The location should then be converted into latitude and longitude. <br />3. ACCURACY. The latitude and longitude should be computed to the nearest <br />second. Coordinates to the nearest tenth of a second may be needed <br />where navigational aids exist orare proposed for installation. <br />Coordination with the appropriate FAA Airway Facilities field office <br />should be made to ascertain the need for accuracy closer than the <br />nearest second. <br />Par 1 Page 1 <br />