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Field Manual 3-34.331 TOPOGRAPHIC SURVEYING 16 January 2001

TOC Chap1 2 3 4 5 6 7 8 9 10 11 AppA AppB AppC AppD Gl Bib

Chapter 10

## Airfield-Obstruction and NAVAID Surveys

This chapter acquaints Army surveyors with the terminology and the requirements for airfield-obstruction and NAVAID surveys. The content is general in nature due to the vast differences in airfield instrumentation, customer requirements, and FAA regulations.

### AIRPORT OBSTRUCTION CHARTS AND NAVAID SURVEYS

10-1. AOCs and NAVAID surveys are extensive field or photogrammetric operations that are required by agreement between the FAA and the USAASA and are specified in AR 95-2. Airfield-obstruction and NAVAID surveying operations involve obtaining accurate and complete NAVAID and associated airport/heliport-obstruction and geodetic-positioning data. A precise geographic position of these navigational facilities is required to support the FAA and a wide range of NAS activities. AOC surveys provide source information on

> > > - Runways and stopways.
> > > - NAVAIDs.
> > > - FAR-77 obstructions.
> > > - Aircraft-movement aprons.
> > > - Prominent airport buildings.
> > > - Selected roads and other traverse ways.
> > > - Cultural and natural features of landmark value.
> > > - Miscellaneous and special-request items.

10-2. AOC surveys also establish or verify geodetic control in the airport vicinity that is accurately connected to the >NSRS. This control and the NSRS connection ensure accurate relativity between these points on the airport and other surveyed points in the NAS, including GPS navigational satellites. AOC data is used to

> > > - Develop instrument-approach and -departure procedures.
> > > - Determine maximum takeoff weights.
> > > - Certify airports for certain types of operations.
> > > - Update official aeronautical publications.
> > > - Provide geodetic control for engineering projects related to runway/taxiway construction, NAVAID positioning, obstruction clearing, and other airport improvements.
> > > - Assist in airport planning and land-use studies.
> > > - Support activities such as aircraft-accident investigations and special projects.

### FAA AND FAR STANDARDS

10-3. FAA Publication 405 (FAA 405) and FAR-77 outline the requirements for AOC surveys. Various areas, surfaces, reference points, dimensions, and specifications used in airfield surveys are described below.

RUNWAYS

10-4. All length and width measurements are determined to the nearest foot. If the runway's threshold is displaced, the distance (in feet) is given from the beginning of the runway's surface. Determine the coordinates (latitude and longitude) of the runway's threshold and stop end at the runway's centerline. Elevations at the runway's threshold, stop end, and highest elevation (within the first 3,000 feet of each runway touchdown zone elevation [TDZE]) should be determined to the nearest 0.1 foot from the MSL. In addition, prepare runway profiles that show the elevations listed above, the runway's high and low points, grade changes, and gradients. Determine the elevation of a point on the instrumented runway's centerline nearest to the instrument landing system (ILS) and the glide-path transmitter to the nearest 0.1-foot MSL.

NAVAIDS

10-5. Airports requiring airfield-obstruction and NAVAID surveys are instrumented runways. The exact point on the radar, the reflectors, the runway intercepts, and the ILS and microwave-landing-system (MLS) components depend on the survey type, the location, and the required accuracy. The requirement to verify the existing ILS/MLS, their proper description, and all components on or near the runway is mandatory. Obtain information for locating and describing all airfield features with help from airfield-operation, maintenance-section, and control-tower personnel. The following NAVAIDs are located on airports:

> > > - ILS.
> > > - MLS.
> > > - Precision approach radar (PAR).
> > > - Airport surveillance radar (>ASR).

10-6. The following NAVAIDs are not located on airports:

> > > - Tactical air navigation (TACAN).
> > > - VHF omnidirectional range (VOR).
> > > - Nondirectional beacon (NDB).
> > > - VOR and TACAN (VORTAC).

OBSTRUCTIONS

10-7. An obstruction is an object or feature protruding through or above any navigational imaginary surface that poses a threat to the safe operation of aircraft. Navigational imaginary surfaces or obstruction identification surfaces (OISs) are defined in FAR-77. In the following paragraphs are some definitions, along with some samples.

FAR-77, Section 77.28, Military-Airport Imaginary Surfaces (Figure 10-1 and Figure 10-2)

Figure 10-1. General Plan View of an OIS

Figure 10-2. Partial Plan View of an OIS

10-8. Related to airport reference points (ARPs). These surfaces apply to all military airports. For the purpose of this section, a military airport is any airport operated by an armed force of the US.

> > > - Inner horizontal surface. An oval plane that is at a height of 150 feet above the established airfield elevation. The plane is constructed by scribing an arc with a radius of 7,500 feet from the centerline at the end of each runway and interconnecting these arcs with tangents.
> > > - Conical surface. A surface extending from the periphery of the inner horizontal surface outward and upward at a slope of 20:1 for a horizontal distance of 7,000 feet to a height of 500 feet above the established airfield elevation.
> > > - <Outer horizontal surface. A plane that is located 500 feet above the established airfield elevation, extending outward from the outer periphery of the conical surface for a horizontal distance of 30,000 feet.

<10-9. Related to runways. These surfaces apply to all military airports.

> > > - Primary surface. A surface located on the ground or on water, longitudinally centered on each runway, and the same length as the runway. The width of the primary surface for runways is 2,000 feet. However, at established bases where substantial construction has taken place according to previous lateral-clearance criteria, the 2,000-foot width may be reduced to the former criteria.
> > > - Clear-zone surface. A surface located on the ground or on water at each end of the primary surface. The clear-zone surface is 1,000 feet long and is the same width as the primary surface.
> > > - Approach/departure-clearance surface. An inclined plane that is located symmetrical from the extended runway's centerline, beginning 200 feet beyond each end of the primary surface at the centerline elevation of the runway's end and extending for 50,000 feet (Figure 10-3). The slope of the approach-clearance surface is 50:1 along the extended runway's centerline until it reaches an elevation of 500 feet above the established airport elevation. The surface then continues horizontally at this elevation to a point 50,000 feet from the beginning point. The width of this surface at the runway's end is the same as the primary surface, then it flares uniformly and the width at 50,000 feet is 16,000 feet.
> > > - Transitional surfaces. These surfaces connect the primary surfaces, the first 200 feet of the clear-zone surfaces, and the approach/departure-clearance surfaces to the inner horizontal surface, the conical surface, the outer horizontal surface, or other transitional surfaces. The slope of the transitional surface is 7:1 outward and upward at right angles to the runway's centerline.

Figure 10-3. Plan and Profile View of the Approach/Departure OIS

FAR-77, Section 77.29, Airport Imaginary Surfaces for Heliports

10-10. These surfaces apply to all military heliports. For the purpose of this section, a military heliport is any heliport operated by an armed force of the US.

> > > - Heliport's primary surface. The primary surface coincides in size and shape with the designated takeoff and landing area of a heliport. This surface is a horizontal plane at the elevation of the established heliport elevation.
> > > - Heliport's approach surface. The approach surface begins at each end of the heliport's primary surface, is the same width as the primary surface, and extends outward and upward for a horizontal distance of 4,000 feet where its width is 500 feet. The slope of the approach surface is 8:1 for civil heliports and 10:1 for military heliports.
> > > - Heliport's transitional surfaces. These surfaces extend outward and upward from the lateral boundaries of the heliport's primary surface and from the approach surfaces at a slope of 2:1 for a horizontal distance of 250 feet from the centerline of the primary and approach surfaces.

FAR-77, Section 77.5, Kinds of Objects Affected

10-11. This section further defines an obstruction and applies to

> > > - Any object of natural growth, the terrain, permanent or temporary construction or alterations (including equipment or materials used therein), and apparatus of a permanent or temporary character.
> > > - Any permanent or temporary existing structure altered by a change in its height (including appurtenances) or lateral dimensions (including equipment or materials used therein).

DATA

10-12. The ARP location (in longitude and latitude) will be determined according to FAA 405. Field elevation is the highest point on any airport landing surface.

### AIRFIELD-DATA ACCURACY REQUIREMENTS

10-13. All contiguous CONUS-, Alaskan-, and Caribbean-area coordinates should be determined based on NAD 83 and/or WGS 84. Geodetic accuracy of orthometric heights are referenced to NAVD 88. The coordinates for the points on the airport require different degrees of accuracy. Tables 10-1 and 10-2 and Tables 10-3, 10-4, and 10-5 are examples of different accuracy standards for airfield data. FAA 405 contains the complete requirements. The horizontal accuracy requirements can be met through third-order, Class II traverse, GPS, or two-point intersection techniques. The vertical accuracy requirements dictate a minimum of third-order differential-leveling techniques.

Table 10-1. Airport-Obstruction Accuracy Requirements

Item | Horizontal (ft) | Orthometric (ft) | Ellipsoidal (ft) | Above Ground Level (ft)
Non-man-made objects and man-made objects less than 200 feet above ground level that penetrate the OISs. | A primary surface. | 20 | 3 | 3 | NA
Those areas of an approach surface within 10,200 feet of the runway's end. | 20 | 3 | 3 | NA
Those areas of a primary transitional surface within 500 feet of the primary surface. | 20 | 3 | 3 | NA
Those areas of an approach/departure surface that are both within 500 feet of the approach surface and within 2,766 feet of the runway's end. | 20 | 3 | 3 | NA

Table 10-2. Visual-NAVAID Accuracy Requirements

Item | Horizontal (ft) | Orthometric (ft) | Ellipsoidal (ft) | Above Ground Level (ft)
Airport beacon | (1) | NA | NA | NA
Visual glide-slope indicators | 20 | NA | NA | NA
Runway end identifier lights (REILs) | 20 | NA | NA | NA
Approach lights | 20 | NA | NA | NA
<NOTE: The horizontal accuracy requirement for items coded "(1)" is 20 feet when located on a public-use airport or military airfield and 50 feet for all other locations.

Table 10-3. Control-Station Accuracy Requirements

Item | Horizontal (cm) | Orthometric (cm) | Ellipsoidal (cm) | Above Ground Level (cm)
Primary airport control station (PACS)1 | 5 | 25.0 | 15 | NA
Secondary airport control station (SACS)2 | 3 | 5.0 | 4 | NA
Wide-Area Augmentation System (WAAS) reference station1 | 5 | 10.0 | 10 | NA
WAAS reference station3 | 1 | 0.2 | 2 | NA
1Accuracies are relative to the nearest NGS-sanctioned continuously operating reference station. 2Accuracies are relative to the PACS and the SACS at the airport. 3Accuracies are relative to the other WAAS reference station at the site.

Table 10-4. Electronic-NAVAID Accuracy Requirements

Item | Horizontal (ft) | Orthometric (ft) | Ellipsoidal (ft) | Above Ground Level (ft)
Air-route surveillance radar (ARSR) | (1) | 100 | 100 | NA
ASR | (1) | 10 | 10 | NA
DME: Frequency paired with localizer Frequency paired with MLS azimuth guidance Frequency paired with NDB Frequency paired with VOR | 1 1 (1) (1) | 1 1 NA NA | 1 1 NA NA | NA NA NA NA
NOTE: The horizontal accuracy requirement for items coded "(1)" is 20 feet when located on a public-use airport or military airfield and 50 feet for all other locations.

Table 10-5. Airport-Runway Accuracy Requirements

Item | Horizontal (ft) | Orthometric (ft) | Ellipsoidal (ft) | Above Ground Level(ft)
Physical end | 1 | 0.25 | 0.2 | NA
Displaced threshold (DT) | 1 | 0.25 | 0.2 | NA
TDZE | NA | 0.25 | 0.2 | NA
Supplemental profile points | 20 | 0.25 | 0.2 | NA

### REPORTING

10-14. The required reporting for airfield surveys is not significantly different from that required for other survey operations. The parent unit will normally require all of the reports listed in Chapter 11 of this manual. In addition to these routine reports, a special report (according to ARs 95-1 and 95-2, >FAA 405, and FAR-77< will be required for the submission of the final data. For quick reference, the required documentation is listed below.

AOC

10-15. An AOC is a 1:12,000-scale graphic depicting FAR-77 guidance. An AOC represents objects that penetrate airport imaginary surfaces, aircraft movement and apron areas, NAVAIDs, prominent airport buildings, and a selection of roads and other planimetric detail in the airport vicinity. Also included are tabulations of runway and other operational data. AOC data is current as of the date of the field survey. The AOC consists of four sections:

> > > - Airport plan (AP).
> > > - Runway plans and profiles (RPP).
> > > - Tabulated operational data (TOD).
> > > - Notes and legends (NL).

10-16. Each section (all contents and the general format) should conform to the sheet style (obstruction chart [OC] 000) represented in FAA 405. An AOC is published on E50 chart paper (or equivalent) with border dimensions of 30 x 42 or 30 x 48 inches. The long dimension may be either in the north-south or east-west direction and should have a -inch space between the border and the trim line. If the AP and the RPP will not fit on the front of the chart, the RPP is printed on the back.

Airport Plan

10-17. The depiction of the AP depends on the surface type and whether an obstruction survey was accomplished. A detailed explanation of what pertinent information to depict is included in FAA 405, Section 10.1.3. For example, an AP for a specially prepared hard surface (SPHS) runway will include the following information:

> > > - Runway's length and width.
> > > - DTs.
> > > - The physical end of the runway.
> > > - Airport elevation.
> > > - TDZE.
> > > - Magnetic bearing.
> > > - Runway numbers.
> > > - Obstructions.
> > > - NAVAIDs.
> > > - Meteorological apparatus.
> > > - ARP.

Runway Plans and Profiles

10-18. A detailed explanation of what information to depict is included in FAA 405, Section 10.1.4. The RPP should include the following:

> > > - Proper angular orientation.
> > > - A horizontal scale of 1:12,000 and a vertical scale of 1 inch equal to 100 feet.
> > > - Adequate area of coverage of the primary and approach surfaces.
> > > - A plan view of the runway as shown on the AP.
> > > - A profile view of objects carried in the plan view.
> > > - A profile view of objects penetrating the approach surfaces.
> > > - The correct approach surface or precise-instrument-runway (PIR) surface.
> > > - The correct numbering scheme of objects in the profile.
> > > - A north arrow.

> > > NOTE: A PIR has an existing instrument-approach procedure that uses an ILS or a PAR. PIR also refers to a runway for which a precision approach system is planned and is so indicated by an FAA-approved airport layout plan, a military-airport layout plan, any other FAA planning document, or a military-airport planning document.

Tabulated Operational Data

10-19. The TOD should show the following:

> > > - The airport location point (ALP) listed in degrees and minutes.
> > > - The ARP listed in degrees, minutes, and three-decimal-place seconds.
> > > - A runway data table with runway numbers, appropriate latitude and longitude coordinates, and TDZEs.
> > > - Geodetic azimuth from the approach end to the stop end, reckoned from the north.
> > > - Additional information pertaining to runways with DTs.

Notes and Legends

10-20. A detailed explanation of what pertinent information to depict is included in FAA 405, Section 10.1.6. The NL should include the following:

> > > - Horizontal datum.
> > > - Vertical datum.
> > > - Map projection.
> > > - Airport elevation.
> > > - A legend.
> > > - Graphic horizontal and vertical scales.

FORMS

10-21. In addition to the AOC, each airfield report requires completion of the following forms:

> > > - DA Form 5821-R.
> > > - DA Form 5822-R.
> > > - DA Form 5827-R.

10-22. An airfield compilation report (DA Form 5821-R) (Figure 10-4) is a tabulation of all the information obtained from the survey. Table 10-6 includes instructions for completing this form.

Figure 10-4. Airfield Compilation Report

Table 10-6. Instructions for Completion of DA Form 5821-R

Block Name | Instruction
Survey agency | The agency conducting the field survey.
Airport name | The official airport name as determined by the FAA.
Identifier | The airport location-identifier designator as listed in FAA Publication 7350.5-V.
City | Self-explanatory.
State | >Self-explanatory.
Edition | The number of times the airfield has been surveyed by the agency listed in the survey-agency block. Identify the original survey as 1 and subsequent surveys as 2, 3, and so on.
Survey date | The year of declination.
ARP | The physical location of the ARP.
ARP latitude | Self-explanatory.
ARP longitude | Self-explanatory.
Delta azimuth or theta angle | The grid convergence for the ARP.
ALP | The physical location of the ALP.
ALP latitude | Self-explanatory.
ALP longitude | Self-explanatory.
Declination | The magnetic declination of the ARP.
Airport elevation (ft) | See the glossary.
Located | A short narrative description (include the latitude and the longitude).
Control-tower floor elevation (ft) | Self-explanatory.
Airport data | Object or airfield feature observed (use additional sheets as required).
Elevation | Self-explanatory.
Airport-data latitude | Self-explanatory.
Airport-data longitude | Self-explanatory.
Year code | The year and month surveyed (for example, April 87 is written 8704).
Remarks | Self-explanatory.
Office code | Leave blank (may be used by other offices).
Runway | The numerical designation of the runway.
DT length | See the glossary.
Runway-end elevation | Self-explanatory.
Runway-end latitude | Self-explanatory.
Runway-end longitude | Self-explanatory.
Width/length | The physical width and length of the runway's surface.
Geodetic azimuth/magnetic bearing | Self-explanatory.
Office code | Leave blank.

10-23. PAR or ground-controlled-approach (GCA) data is entered on DA Form 5822-R. The completion of this form is self-explanatory (Figure 10-5).

Figure 10-5. PAR Data

10-24. ILS data is entered onDA Form 5827-R (Figure 10-6). The completion of this form is self-explanatory.

Figure 10-6. ILS Data