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<br />and maintenance of costly ground-based <br />transmission equipment at the airport. <br />As mentioned previously, the FAA is <br />proceeding with a program to transition <br />from existing ground-based navi- <br />gational aids to a satellite-based <br />navigation system utilizing GPS <br />technology. Currently, GPS is certified <br />for en route guidance and for use with <br />instrument approach procedures. The <br />initial GPS approaches being developed <br />by the FAA provide only course <br />guidance information. By the year <br />2003, it is expected that GPS <br />approaches will also be certified for use <br />in providing descent information for an <br />instrument approach. This capability is <br />currently only available using an <br />instrument landing system. <br /> <br />GPS approaches fit into three <br />categories, each based upon the desired <br />visibility minimum of the approach. <br />The three categories ofGPS approaches <br />are: precision, non-precision with <br />vertical guidance and non-precision. To <br />be eligible for a GPS approach, the <br />airport landing surface must meet <br />specific standards as outlined in FAA <br />AC 150/5300-13, Airport Design, <br />Appendix 16, Change 6. At the time <br />this chapter was written, the new <br />standards were in draft form and had <br />not been finalized. Based upon this <br />draft circular, only Runway 12 meets <br />the requirements for a precision <br />approach since it is equipped with the <br />required approach lighting system, <br />runway markings and runway edge <br />lighting. It should be expected that the <br />ILS approach will eventually be <br />replaced by GPS as the FAA transitions <br />to GPS as the sole means for <br />navigation. <br /> <br />3-11 <br /> <br />Runway 12 is equipped with a straight- <br />in instrument approach procedure <br />utilizing the instrument landing system <br />(ILS). Runway 12 is also served by a <br />GPS and NDB approach. Facility <br />planning should include providing an <br />additional precision GPS approach from <br />the south to complement approach <br />capability to Runway 12. <br /> <br />Since instrument approaches can be <br />established at the airport using GPS, <br />which does not require the installation <br />of costly ground-based navigational <br />aids, instrument approach capability <br />can be planned for each end of the <br />crosswind runway. Since the primary <br />runway is expected to provide precision <br />approach capability to each runway <br />end, only limited approach capability <br />would be required to each end of the <br />crosswind N onprecision approaches <br />with visibility minimums of at least <br />greater than one mile should be <br />planned for each end of the crosswind <br />runway. <br /> <br />AIRFIELD <br />SAFETY STANDARDS <br /> <br />The FAA has established several <br />imaginary surfaces to protect aircraft <br />operational areas and keep them free <br />from obstructions that could affect the <br />safe operation of aircraft. These include <br />the object free area (OFA), obstacle free <br />zone (OFZ), and runway safety area <br />(RSA) . <br /> <br />The OFA is defined as "a two <br />dimensional ground area surrounding <br />runways, taxiways, and taxilanes which <br />is clear of objects except for objects <br />