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62 Key Insights An airspace composite map is intended to aggregate and display in a simplified, single composite view the complex variety of surfaces that are most critical for an airport to protect from encroachment. The creation of the composite map involves many of the same steps that are carried out by any airport conducting a comprehensive airport obstruction evaluation. Composite map development requires a high level of expertise but substantially simplifies future obstruction analyses and airspace evaluations. Key Definitions Instrument Flight Procedures (IFPs) Information Gateway: A centralized instrument flight procedures data resource that provides up-to-date information on published aeronautical and instrument flight procedures charts and instrument flight procedures production plans, coor- dination forms, and documents. National Flight Data Center aeronautical data: A repository of aeronautical information on all the components of the NAS. The data are used to develop and update instrument flight procedures, aeronautical charts, and all related publications. 6.1 The Composite Map Approach The composite map is a three-dimensional model of an airportâs airspace, blending various imaginary and design airspace surfaces into one composite that shows the height of the desired most critical surface over any given point. The use of the term âdesiredâ as opposed to âlowestâ is deliberate. Many imaginary surfaces protecting different parts of the NAS exist over any given point on which a property owner may wish to establish a structure. However, not all of these surfaces are required to be clear of obstacles. Some may just require that the obstacle that penetrates the surface is studied by the FAA and marked and lighted. Additionally, the airport sponsor may choose to trade more strin- gent protection of one runway and its approaches for a more lenient approach to development at the ends of a less critical runway. The composite map joins all critical surfaces the airport intends to protect and shows them as a single model, similar to a topographic map, where the contours represent the heights of imaginary airspace surfaces. Superimposing this map over aerial photographs C H A P T E R 6 Airspace Composite Map and Development Methodology
Airspace Composite Map and Development Methodology 63 or parcel maps allows all stakeholders to view the most critical surface heights over any given geographical point without relying on knowledge of a multitude of complex airspace regulations. It should be noted that a composite map of airspace surfaces is intended to establish the ulti- mate lowest limits of the airportâs airspace up to which development should be allowed. Once a composite map is developed and established, it will be very difficult to lower or âregainâ airspace. Therefore, consideration must be given to an airportâs long-term, ultimate build-out poten- tial. This not only includes the physical layout of the runways and approaches but also future air service requirements (e.g., serving airlines that may apply the ICAO OEI OIS requirements, as opposed to FAA AC 120-91). Airport sponsors at all types of airports are expected to answer the question posed by property owners: âWhat is the allowable height that I may build to on my parcel?â As shown in Chapter 3, due to the complexity and variety of multiple surfaces and criteria, answering this question with certainty may not be an easy and straightforward task, especially at more complex airports. Research and field experience has shown that airports that use a composite map of their airspace surfaces for obstruction management purposes do so because of the complexity of the multiple surfaces that are required to be kept clear to support their operations. Airports that have developed and use a composite map to address airspace questions find that the map removes some of the complexity from the various airspace surfaces and improves the consistency of obstruction analyses. The results of the analysis undertaken in the development of a composite map to identify critical surfaces should be reflected in airport protection zoning for the airport. If a local jurisdiction does not have airport protection zoning regulations, a composite map can be utilized to provide a detailed analysis of impacts on operations and to visually pres- ent the results of the analysis to nonaviation stakeholders as a case against airport or airspace encroachment. 6.2 Selecting the Composite Map Surfaces There are several different types of surface or criteria that can be developed and joined in a comprehensive composite map. The types and extent of the composite surfaces depend on the airportâs needs and on how the airport sponsor intends to use the map to conduct business. Airport Use of a Composite Map of Airspace Surfaces Bostonâs Logan International Airport is an airport surrounded by multiple juris- dictions, none of which has adopted airport protection height zoning. Composite mapping of the critical surfaces over the South Boston Waterfront district began nearly two decades ago due to the area undergoing a redevelopment boom as an extension of the downtown business district. Having a composite map of the critical airspace surfaces allowed the city planning staff to identify appropriate future land uses based on allowable building heights across an area affected by four different runways. The composite map of critical surfaces was composed in 2008 and distributed to local development authorities for reference.
64 Best Practices for Airport Obstruction Management Guidebook Four main categories of imaginary surfaces may need to be considered when developing a composite map: â¢ CFR 14 Part 77, Civil Airport Imaginary Surfaces (FAR Part 77.19) â¢ FAA AC 150/5300-13A: Airport Design surfaces â¢ FAA Order 8260.3D (TERPS) surfaces â¢ Air carrier OEI OIS surfaces (FAA AC 120-91 or ICAO Annex 6) Each of these categories, including how impacts on those surfaces and criteria affect the air- port, are described in Chapter 3. FAR Part 77.19 The surfaces covered by FAR Part 77 for the purpose of obstruction identification and evalua- tion vary based on the airportâs specifics and will range in dimension from airport to airport. For the purposes of composite map development, the typical set of imaginary surfaces covered by FAR Part 77.19, described in Section 3.2, should be considered for composite surface modeling and analysis, including the following: â¢ Primary surface â¢ Approach surface â¢ Transition surface â¢ Horizontal surface â¢ Conical surface When creating a FAR Part 77 surface composite, special attention should be paid to the PIR approach surface, if one is applicable. The PIR approach surface originates at the end of the primary surface and extends to a distance of 50,000 feet. In the area where the PIR approach surface overlies the horizontal and conical surfaces, those surfaces are the lowest surfaces over any point on the ground within their horizontal confines and, therefore, should be used for map development and contouring, as shown in Figure 6.1. Source: Planning Technology, Inc. Map data: Google, Image Landsat/Copernicus, Data SIO, NOAA, U.S./Navy, NGA, GEBCO. Figure 6.1. FAR Part 77.19 cut-away model.
Airspace Composite Map and Development Methodology 65 As the approach surface continues at a shallower slope than the conical surface, it re-emerges as the lowest and more critical surface. Although the conical surface forms a complete ring surround- ing the outer limits of the horizontal surface, neither the horizontal surface nor the conical surface is modeled in the areas where the approach and transitional surfaces are lower over the same point. FAR Part 77 typically serves as the composite mapping starting point for all airports because it defines the regulatory and filing requirements and, in many cases, it may align with state or local regulations. However, when an airport needs to protect surfaces that are lower than FAR Part 77, as described in Chapter 3, a composite map is a valuable tool. Airport Design Criteria Airports developing a composite map should also consider the importance of including the imaginary surfaces that are part of the airport design criteria in FAA AC 150/5300-13A. Although these surfaces are primarily contained on the airport, there are three sets of surfaces that will extend beyond the airportâs boundaries: the TSS, instrument approaches with VGS, and the 40:1 departure surface used by FAA Airports for airport planning purposes. The airport sponsor should also identify the most critical TSS type or VGS criteria that the airport intends to protect because each runway end may have multiple splays for the same type of surface, such as approach, if there are multiple types of approaches serving a particular runway end. Because these criteria may affect the siting of the runway thresholds, availability of approaches, and airport utility, it is important for airport sponsors to identify the most critical criteria and include them as a part of an overall composite. TERPS The TERPS surfaces described in Section 3.4 of this guidebook, for the most part, are higher than FAR Part 77.19 surfaces. However, there are areas where this is not the case, and any airport with instrument procedures should be aware of these cases. While Section 3.4 covers the special considerations in TERPS analysis, the same or similar considerations are appli- cable during the development of a composite map. TERPS criteria are complex and vary from case to case. Therefore, the listing of special considerations in Section 3.4 is not intended to be a complete list, but demonstrates the need for particular scrutiny of TERPS surfaces when developing composite maps. Nonvertically Guided Approaches and Offset Approaches As discussed earlier in this guidebook, FAR Part 77.19 criteria for approach surfaces evaluate a continuous and progressively sloped surface, while the TERPS design criteria for instrument approaches without vertical guidance use a step-down method. Therefore, the OCS that the FAA uses to establish the approach minimums and determine whether the approach may be authorized may be located below the FAR Part 77 approach surface. Figure 6.2 shows an FAR Part 77.19 precision approach surface with a typical, nonvertically guided, or nonprecision, OCS overlaid as an example of such a condition. In addition, the FAR Part 77 approach surface is centered on the extended runway centerline. However, in certain circumstances (e.g., due to the presence of obstacles) straight-in approaches are offset and intersect the extended centerline just beyond the end of the runway. The aircraft navigational technology used for complex instrument approaches allows for multiple turns along the final approach course before aligning with the runway centerline. These turns have to be modeled as a part of the composite map because impacts on the applicable surfaces may come from beyond the lateral confines of the approach surface.
66 Best Practices for Airport Obstruction Management Guidebook Runways for which takeoffs are authorized during instrument meteorological conditions benefit from having the instrument departure surfaces modeled as a part of the composite map. As described in Section 3.4, although the departure surfaces should be clear of impacts, the FAA provides several measures to accommodate the existing penetrations. During the development of the departure surface element for the composite map, the airport sponsor should take into account any such measures that may have been implemented by the FAA and may affect the overall design of the composite surface. Figure 6.3 shows the departure surface as it relates to the FAR Part 77.19 surfaces. Including standard departure surfaces in a composite map is important, even if they are already partially penetrated. This allows the airport to protect the remaining airspace that is available for departing aircraft, which may not be able to achieve a higher nonstandard climb gradient. Other Approaches and Visual Aid Critical Areas Visual aid critical areas must also be considered during composite map development. In the case of a typical precision instrument approach (such as an ILS), the surfaces associated with the final approach are generally less restrictive than the FAR Part 77 imaginary surfaces. However, there may be additional visual aids supporting that approach, such as a PAPI, which has its own associated OCS. Figure 6.4 shows a typical three-degree PAPI OCS, as well as an ILS precision approach and other FAR Part 77.19 surfaces. OEI OIS Chapter 3 discusses the need to evaluate additional surfaces for those runways supporting air carrier operations. As OEI OISs are often below FAR Part 77.19 and TERPS surfaces, modeling the appropriate surfaces as a part of the composite map development process is critical to main- taining the economic viability of air carrier operations. Source: Planning Technology, Inc. Map data: Google, Image Landsat/Copernicus, Data SIO, NOAA, U.S./Navy, NGA, GEBCO. Figure 6.2. FAR Part 77.19 versus nonvertically guided approach OCS.
Airspace Composite Map and Development Methodology 67 Source: Planning Technology, Inc. Map data: Google, Image Landsat/Copernicus, Data SIO, NOAA, U.S./Navy, NGA, GEBCO. Figure 6.3. FAR Part 77.19 versus standard departure (40:1). Source: Planning Technology, Inc. Map data: Google, Image Landsat/Copernicus, Data SIO, NOAA, U.S./Navy, NGA, GEBCO. Figure 6.4. Part 77.19 versus ILS final approach and PAPI OCS.
68 Best Practices for Airport Obstruction Management Guidebook While the FAA continues to treat OEI OIS impacts as an economic issue for air carriers, including the OEI OIS in the composite map assists airports seeking to protect air carrier service from degradation due to OEI surface impacts. Figure 6.5 illustrates a typical OEI straight-ahead surface based on a slope of 62.5:1 in relation to the FAR Part 77.19 cut-away model. 6.3 Building a Composite Map Airports surveyed as a part of NCHRP Project 09-16 that have developed airspace surface composite maps used a multistep process that included the following: â¢ Determining which of the aforementioned surfaces would be applicable â¢ Collecting the obstruction data â¢ Individually constructing the surfaces with three-dimensional design software Individually constructing the surfaces produces a three-dimensional âwireframeâ model, which can be compared to other models that use spatial analysis tools to determine which point is the lowest for each of the various designed surfaces. This approach requires the skills and expertise of airport staff, or a consultant experienced in airspace surface development, and soft- ware designed for three-dimensional applications. The software packages used for these types of analyses are developed to suit a variety of applications and, therefore, have numerous variable settings that may affect the outcome of the process. For example, some applications allow for variability in the precision of the final surface. The contours of a composite map for the airport may be set in 25- or 50-foot increments; however, the precision to which the mapâs surfaces are built will determine how far the user can âzoom inâ and still receive reliable height information. While each airport and set of Source: Planning Technology, Inc. Map data: Google, Image Landsat/Copernicus, Data SIO, NOAA, U.S./Navy, NGA, GEBCO. Figure 6.5. FAR Part 77.19 versus the OEI surface.
Airspace Composite Map and Development Methodology 69 circumstances is different, the basic steps outlined below apply to the process of map devel- opment for each facility. Data Collection Data collection for obstruction management purposes is discussed in Chapter 3. For the purposes of composite map creation, the process of data collection is largely similar to other obstruction management efforts and involves two considerations. The composite map creator must (1) establish the applicable airspace surfaces and (2) determine the source of obstacle data to be used for airspace analysis, if applicable. Surface Selection and Data Gathering The surface data required will vary depending on which surfaces the airport intends to model and make part of the composite: â¢ FAR Part 77 and airport design criteria: Data requirements for this effort will include all the data required to determine existing and future approach types, runway coordinates, and runway centerline profiles. Most, if not all, of the data required for this step can be obtained from the ALP and the National Flight Data Centerâs aeronautical database. â¢ TERPS: For this effort, data are collected on all the instrument approach and departure pro- cedures. Most of the data can be found through the FAAâs Instrument Flight Procedures Information Gateway. â¢ OEI: The amount of data collection required for this task will greatly vary, depending on the airlines that serve the airport and the obstacles surrounding the airport. Straight-out pro- cedures are easily modeled using the standards in AC 120-91 and ICAO Annex 6; however, turning procedures will depend on individual airlines, aircraft types, standards used, and many other factors. The airline-specific data can be obtained through coordination with the specific air carriers. It is important to note that the selection of surfaces to include on a composite map should focus on identifying surfaces that are most critical to the airportânot necessarily surfaces that are the lowest. The selection should focus on measures that are subjective and dependent on the particular airportâs specifics. For example, the airport may elect to use a TERPS nonprecision final approach segment for a composite map model, while omitting the inclusion of an FAR Part 77 precision instrument approach surface that is more restrictive. This can be done if the precision instrument approach is protected by monitoring and evaluating the TERPS surfaces for that or other established approaches. Determining which surfaces to elect as âcriticalâ requires professional judgement and a clear understanding of the direct and indirect consequences of failing to protect a particular surface. Obstacle Data Although an analysis of obstacles is not required for composite map development, such an analysis is usually carried out in conjunction with an updated airport survey to provide current information for surfaces, such as OEI surfaces, which vary depending on the existing obstacles. Likewise, if a surface is already penetrated by numerous obstacles, this may affect the decision on whether or not it is appropriate to include it in the composite map. The sources for obstacle data include the following: â¢ DOF: A repository of man-made obstacles surrounding airports. â¢ Airports GIS: Sets the standards by which all airport surveys are conducted. The requirements for data collection are in FAA AC 150/5300-16, -17, and -18. â¢ OE/AAA: A repository of all obstacle data collected from the submitted FAA Form 7460-1.
70 Best Practices for Airport Obstruction Management Guidebook Develop the Initial Composite To get an initial picture of how the various surfaces around the airport intersect, a good place to start is combining all the standard surfaces associated with the airportâs FAR Part 77.19, OEI, and airport design requirements with the TERPS surfaces associated with any published instru- ment procedures. This initial composite map will represent the lowest-case scenario for the majority of the surrounding airport environs. By combining the obstacle data collected from the various databases noted above with the initial composite map, the airport can identify areas where it may want or need to modify the critical surfaces based on significant obstructions. If the goal of the composite map is to identify proposed obstacles that merit additional study or to eliminate unnecessary evalua- tions of future obstacles that are shielded or shadowed by existing obstacles, then using one of the higher surfaces over those areas may be more appropriate. This approach to surface modification has been implemented at most of the urban airports surveyed that have devel- oped composite maps, including Bostonâs Logan International, Miami International, Orlando Executive, Phoenix Sky Harbor International, and San Jose International airports. Each of these composite maps includes a âdowntownâ zone that is defined, yet does not include the standard FAR Part 77.19 surfaces as the controlling surfaces, even though they are lower than the other surfaces in the composite map. It is common for airports to have penetrations to their imaginary surfaces defined in FAR Part 77.19. Rather, these airports have gone through a process to identify the surfaces that are most critical to protect, and then have worked to protect those surfaces. Identify Modifications for Special Circumstances Under certain circumstances, an airport may choose to simplify its composite map and not show every surface, instrument procedure type, and variation. For example, Phoenix Sky Harbor International Airport chose to simplify its composite map surfaces so that they could be more easily incorporated into the cityâs height zoning ordinance. The airport established a series of baselines from which distances to parcels can be measured and the heights of the surfaces con- tained on the composite map over a parcel can be easily calculated. Additionally, the special considerations discussed in Section 3.7 may require particular modifications of the model to be carried out to account for those circumstances. Final Composite Once a list of applicable surfaces has been developed and any of the modifications to the com- posite map to account for the special circumstances discussed above has been implemented, a final composite map may be developed. Similar to the initial composite map, the final composite and its level of complexity depends on the airport and the way in which the airport intends to use the composite map for obstruction management. This chapter describes only a sample of the different surfaces the FAA analyzes during the obstruction evaluation process that can be considered in the development of a composite map. Figure 6.6 depicts a composite map using just these surfaces and assuming the lowest surface over any given point prevails to demonstrate the overlapping that occurs. The com- plexity of the overall composite map multiplies when considering parallel, crossing, and con- verging runways; turning OEI corridors; missed approach surfaces; and offset approaches. Figure 6.7 shows the same surfaces as Figure 6.6 in a top-down view to illustrate composite complexity.
Airspace Composite Map and Development Methodology 71 Source: Planning Technology, Inc. Map data: Google, Image Landsat/Copernicus, Data SIO, NOAA, U.S./Navy, NGA, GEBCO. Figure 6.6. Sample composite map profile view. Source: Planning Technology, Inc. Map data: Google, Image Landsat/Copernicus, Data SIO, NOAA, U.S./Navy, NGA, GEBCO. Figure 6.7. Sample composite map plan view.