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APPENDIX Light Detection and Ranging (LIDAR) Sample Specifications of Airborne LIDAR for Airport Obstruction Surveys The sample specifications and guidelines contained in this Scope of Work (SOW) document are intended for conducting airborne LIDAR surveys and using the p oint clo ud" data in combination with aerial imagery for airport obstruction analysis. However, this document is not approved by the Federal Aviation Administration at this time and it shall not be considered as an interpretation or statement of FAA policy. Contractors seeking information on FAA-approved airport obstruction survey standards are advised to contact the FAA directly. Table of Contents Subject Page 1 GENERAL ....................................................................................................................................... A-2 2 GOVERNMENT (AIRPORT SPONSOR/FAA/NGS) ....................................................................... A-3 3 DELIVERY SCHEDULE AND DATA FLOW ................................................................................... A-4 4 EQUIPMENT AND MATERIAL ....................................................................................................... A-6 5 POINT SPACING ............................................................................................................................ A-9 6 RADIOMETRIC QUALIFICATION TEST ...................................................................................... A-10 7 SPOT SPACING QUALIFICATION TEST .................................................................................... A-12 8 SYSTEM CALIBRATION .............................................................................................................. A-13 9 MISSION PLANNING AND CLEARANCES ................................................................................. A-15 10 EYE SAFETY ................................................................................................................................ A-17 11 IMAGERY ...................................................................................................................................... A-18 12 WEATHER AND TIME OF YEAR ................................................................................................. A-18 13 POSITIONING AND ORIENTATION FOR THE DATA ................................................................. A-19 14 ANALYSIS WORKFLOW AND OUTLIER REMOVAL .................................................................. A-21 15 DATA LABELING .......................................................................................................................... A-23 16 DATA SHIPMENT AND PROCESSING ....................................................................................... A-23 17 DELIVERABLES ........................................................................................................................... A-23 18 REVIEW ........................................................................................................................................ A-25 19 REFERENCES .............................................................................................................................. A-26 20 TERMINOLOGY AND DEFINITION RELATED TO GROUND-BASED GPS DATA................. A-27 21 ACRONYMS.................................................................................................................................. A-29 A-1

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1 GENERAL Airport obstruction surveys provide safety critical source data used by the Federal Aviation Administration (FAA) to develop instrument approach procedures, determine maximum takeoff weights for aircraft, update aeronautical publications, and perform other functions. The primary objective of an airport obstruction survey is to accurately geolocate objects and obstacles that may penetrate a specified FAA Obstruction Identification Surfaces (OIS). Penetrating objects are termed "airport obstructions." Examples of typical types of obstructions include trees, buildings, towers, poles, antennas, and terrain. The Aeronautical Survey Program (ASP) of the National Geodetic Survey (NGS) established at National Oceanic and Atmospheric Administration (NOAA), under an interagency agreement with the FAA, has carried out obstruction surveys in the past using FAA 405, Standards for Aeronautical Surveys and Related Products (U.S. Dept. of Transportation, 1996). The FAA 405 document has been superseded by the current updated FAA Advisory Circular (AC) standards. The current FAA standards require NGS to conduct quality review and independent verification and validation of obstruction survey data. This Scope of Work (SOW) defines survey specifications and requirements for LIDAR data acquisition and processing to support the ASP. Additional project instructions included in contract agreement for an airport will provide project-specific survey information. General specifications, standards, guidelines, and additional requirements for airport obstruction surveys are contained in the following FAA ACs: AC 150/5300-16A, General Guidance and Specifications for Aeronautical Surveys: Establishment of Geodetic Control and Submission to the National Geodetic Survey, September 15, 2007. AC 150/5300-17B, General Guidance and Specifications for Aeronautical Survey Airport Imagery Acquisition and Submission to the National Geodetic Survey, US Dept. of Transportation, September 28, 2008. AC 150/5300-18B, General Guidance and Specifications for Submission of Aeronautical Surveys to National Geodetic Survey (NGS): Field Data Collection and Geographic Information System (GIS) Standards, US Dept. of Transportation, May 21, 2009. The following conventions have been adopted for this SOW document. The term "shall" means that compliance is required. The term "should" implies that compliance is not required, but is strongly recommended. All times shall be recorded in Coordinated Universal Time (UTC). The Survey Acquisition Contractor (SC) shall be referred to as "Contractor" in the SOW document. LIDAR data acquisition for airport obstruction surveying is very different than for other applications, such as floodplain mapping or bare-earth terrain mapping. For this reason, this docu ment contains detailed information on collecting LIDAR data for obstruction survey purposes. The following list outlines some of the most important considerations in collecting LIDAR for airport obstruction surveys and references the corresponding sections of this document: A. Multiple Look Angles. To achieve a high probability of detection and to assist in distinguishing between real objects and noise in the point cloud data, it is important to scan each section of the survey area from multiple look angles (i.e., different viewing geometries). One way to achieve this is using a combination of tilt (or "forward look") angles. This method is advantageous in obstruction surveying in that it yields strong geometry (high point density on vertical objects) and radiometry (return signal strength), while simultaneously increasing probability of obstruction detection and reducing probability of false alarm (or "false objects"). (See Sections 4.1 and 5.2.) B. Horizontal Point Spacing. The density of laser points on the ground is a key factor in the ability to detect obstructions. Airport obstruction surveys typically require "ultra-dense" LIDAR as compared with other applications, such as floodplain mapping. The horizontal point spacing in both the along-track and across-track directions must meet the specifications contained in this document. (See Section 5.1.) C. Vertical Point Spacing. Because many obstructions are tall, small-diameter objects, such as poles, the vertical point spacing is also a key consideration. The vertical point spacing, defined as the vertical distance between points from consecutive scan lines on the face of a vertical surface, is only applicable to tilted systems. (See Section 5.2.) A-2

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D. Mission Planning. The mission parameters used in obstruction surveying are different than those typically used for other applications, such as bare-earth terrain mapping. In addition to choosing parameters that will meet the required horizontal and vertical point spacing, radiometric considerations (i.e., those related to the received signal strength) must be taken into account. To ensure that the received signal from small-diameter, low-reflectance obstructions, such as antennas or poles, will be above the receiver detection threshold, it is typically necessary to use a narrow beam divergence and fly as low as possible, taking into account eye-safety limits and other considerations. Additionally, swath overlap, cross-lines, and other mission planning parameters must be carefully planned based on the unique considerations involved in airport obstruction surveying, including precautions taken to avoid missed objects, as illustrated in Figures 9.1, 9.2, and 9.3. (See Sections 9.1 and 9.2) E. Radiometric Performance. The radiometric performance of the LIDAR system is critical in obstruction detection in that the received signal from small diameter, low-reflectance obstructions (e.g., dark- colored poles and antennas) must be above the receiver detection threshold for these objects to be detected and successfully mapped. LIDAR systems to be used in obstruction surveying must pass the radiometric qualifications test described in this document. Section 6 contains a recommended radiometric qualifications test for LIDAR systems to be used in obstruction surveying, and Section 8.3 describes an additional in situ test of the system's ability to detect small-diameter, low-reflectance objects. F. Processing. For airport obstruction surveys, it is critical that full LIDAR point cloud containing ALL laser returns be used (i.e., first, last, and all intermediate returns, with no points removed or filtered out). Additionally, it is absolutely critical to start with the data in point cloud format; interpolated digital surface models (DSMs) are unacceptable as input to the processing, since 2D grids of elevation values cannot adequately represent vertical structure. Additionally, it is important to emphasize high probability of detection, PD, on vertical objects in any vertical object detection algorithm employed in the post processing (see Section 14). A generic OIS processing workflow is outlined Figure 14.1. G. Imagery. Aerial photography (digital or film) is important in that it assists in attributing obstructions and in distinguishing real features from false returns, as well as providing an independent source data set for validation and verification. (See Section 11.) 2 GOVERNMENT (AIRPORT SPONSOR/FAA/NGS) 2.1 PROPERTY OF DATA All original data, from the instant of acquisition, and other deliverables required through this contract, are and shall remain the property of the airport sponsor and/or United States Government, if not stated otherwise in project instructions. This includes data collection within and outside the project area. These items include the Contractor- furnished materials. Refer to AC 150/5300-18B for specific guidelines related to survey project administration and Contractor's responsibilities. 2.2 PROVIDED BY GOVERNMENT The government will provide to the Contractor: A. PROJECT INSTRUCTIONS Project instructions are included in a separate document that provides specific project information, contains any unique project requirements, and may have the following attachments: Maps showing the project area OIS requirements A-3

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B. LIDAR SURVEY ACQUISITION REQUIREMENTS (this SOW document) C. Surface Model Library (see Section 14.1) D. REJECTED DATA If data are rejected by FAA/NGS, sample data will be sent upon request showing the problem areas. 3 DELIVERY SCHEDULE AND DATA FLOW 3.1 REGULAR PRODUCTION Any request to deviate from these standards shall be submitted, in advance of the data acquisition, to FAA/NGS for written approval. 3.1.1 DATA ACQUISITION STANDARDS A. Global Positioning System (GPS) Position Dilution of Precision (PDOP) shall be <3. B. Unless otherwise stated in the project instructions, horizontal along-track and across-track point spacing shall not exceed the limits specified in Table 5.1. C. Unless otherwise stated in the project instructions, vertical point spacing shall not exceed the limits specified in Table 5.1. D. Aircraft bank angle shall not exceed 20 degrees. E. Other mission parameters including flightline and flying height shall be set based on the specifications contained in Section 9.1. 3.1.2 DATA PROCESSING A. The format of the data shall be latitude, longitude referenced to the North American Datum of 1983 (NAD 83) and an epoch date shall be included, such as NAD 83 (1986) or NAD 83 (2007). B. The vertical datum is the North American Vertical Datum of 1988 (NAVD 88). To conform to aeronautical conventions and FAA standards, elevation units are U.S. Survey feet. C. The geoid model to be used in converting from GPS-derived ellipsoid heights to NAVD 88 orthometric heights is GEOID03 or the most current version. For Geoid information see: www.ngs.noaa.gov/GEOID. D. No points shall be removed (filtered out) from the LIDAR point cloud data. Outliers shall be classified as "withheld" in the file, in accordance with the LAS file formatting requirements. (See Section 14.2). E. The Contractor shall ensure complete coverage of the OIS. There shall be no "holidays" in the data (no data gaps) anywhere within the OIS. F. The Contractor shall record all processing steps and software used including version numbers. G. The Contractor shall use either Rapid or Precise orbits (but not UltraRapid orbits) for GPS processing. 3.1.3 ACCURACY STANDARDS Accuracy requirements for airport surveys are a function of the survey type, which is specified by the FAA and listed in the individual project instructions. Additional information on accuracy requirements can be found in FAA Order 8260.19, Flight Procedures and Airspace (U.S. Department of Transportation, 1993). More recent information regarding these accuracy requirements and OIS is found in the following FAA ACs: AC 150/5300-17B, General Guidance and Specifications for Aeronautical Survey Airport Imagery Acquisition and Submission to the National Geodetic Survey, US Dept. of Transportation , September 28, 2008. AC 150/5300-18B, General Guidance And Specifications For Submission Of Aeronautical Surveys To NGS: Field Data Collection And Geographic Information System (GIS) Standards , US Dept. of Transportation, May 21, 2009. A-4

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To ensure high-quality data, the Contractor may be required to perform a standard accuracy assessment and/or obstruction detection accuracy assessment on the LIDAR data. The individual project instructions will list the specific requirements. Minimum 30 accuracy checkpoints shall be used for LIDAR survey unless otherwise required in project instructions and these shall be referenced to the National Spatial Reference System. If Contractor proposes to perform less number of LIDAR accuracy checkpoints then prior permission shall be obtained in advance from FAA/NGS. Minimum nine imagery ground control points for georeferencing imagery and an additional minimum five accuracy checkpoints are required for aerial imagery/photo. The pre-marked imagery ground control points and accuracy checkpoints should be of suitable type and location such that they can be detected in both imagery/photo and LIDAR data sets. Accuracy checkpoints for LIDAR can be the same locations used for imagery accuracy checkpoints and imagery control GPS ground stations. These accuracy checkpoints are not to be confused with the ground GPS base station data required and used for post-processing airborne GPS data for both LIDAR and aerial imagery. (See Sections 13.1, 13.2, and 21.) The standard accuracy assessment, if required, will be performed in accordance with the "ASPRS LIDAR Guidelines Vertical Accuracy Reporting for LIDAR Data" (ASPRS, 2004) and the corresponding horizontal accuracy reporting guidelines. Only the "fundamental" vertical accuracy, as defined by ASPRS, needs to be calculated and reported; "supplemental" vertical accuracies for various ground cover classes do not need to be reported. Accuracy shall be reported at the 95% confidence level. All accuracy checkpoints shall be referenced to the National Spatial Reference System (NSRS) and, preferably, tied to the National Continuously Operating Reference Stations (CORS) network. These checkpoints are not to be confused with ground GPS ground control stations, but maybe georeferenced using standard GPS techniques as described in the ASPRS Guidelines. In accordance with the ASPRS Guidelines (ASPRS, 2004), the checkpoints should be at least three times more accurate than the data being tested and should be well distributed throughout the dataset. The checkpoints should be located on open terrain of constant gradient for which the "first return" and "last return" elevations are equal. A final report shall be generated following this testing process and delivered to FAA/NGS. This report shall contain a table summarizing the results including the number of checkpoints, and the mean, median, mode, skewness, and standard deviation of the dataset, in addition to the Accuracy(z), as defined in the ASPRS Guidelines. If obstruction detection accuracy assessment is required, the Contractor can contact NGS to obtain the analysis software and specifications, as well as the independent field-surveyed data set. Obstruction detection accuracy assessment is performed by comparing the LIDAR data against an independent high-accuracy field-surveyed obstruction data set. The software used in the obstruction accuracy assessment compares the data sets and computes the percent detection, as well as the horizontal and vertical RMSE for obstruction data points in the LIDAR data set. (See Section 8.) 3.2 DATA FORMAT AND STANDARDS A. Format of deliverables shall be: 1. LIDAR point cloud: LAS 1.2 or more recent version of the LAS standard will be required and specified further in the project instructions. The LAS file shall contain all recorded returns (i.e. first, last, and any intermediate returns), return number, scan angle, scan direction, GPS time, intensity, X, Y, Z, and the edge of the flight line (if available). If digital aerial imagery is collected concurrently the LAS file may be version 1.2 and contain an associated red, green, blue (RGB) values (optional), as well as LIDAR intensity (required) for each LIDAR point. Details on LAS format standards can be found at: http://www.asprs.org/society/committees/LIDAR/LIDAR_format.html. No points shall be removed from the LIDAR point cloud. 2. "Raw" observation files (i.e., laser ranges, scanner angles, position and orientation data, with applicable time tags, waveforms if available, etc., as taken off the aircraft at the end of the flight) enabling NGS to post-process the raw data to generate point clouds. 3. Imagery: GEOTIFF (see Section 11). Follow AC 150/5300-17B specifications. A-5

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B. The media for deliverable shall be an external Hard Drive (either SATA or eSATA format) formatted NTFS. Contractor shall maintain a copy of the data until FAA/NGS acknowledges receipt and confirms data is valid. 3.3 DATA FLOW Survey Acquisition Contractor, referred to as SC or Contractor, shall submit survey plan and quality control plan to Airport Authority/FAA for NGS review. Survey work is authorized by Airport Authority only after approval from FAA. Survey data shall be handled in the following sequence: A. SC acquires data as per SOW and FAA accuracy requirements. B. SC processes data to FAA/NGS specifications. C. SC validates data versus check points. D. SC ships data to FAA/NGS as per SOW. E. FAA/NGS receives data, acknowledges receipt of data, reviews data, conducts verification and quality checks, and notifies SC of review outcome. F. If during the FAA/NGS review, the data are found to not meet the SOW, the Contractor may be required to re-acquire the data. 3.4 COMPLETION DATE All deliverables shall be received by FAA/NGS, as specified, no later than the date in the project instructions. 4 EQUIPMENT AND MATERIAL 4.1 LIDAR SYSTEM The Contractor shall have several options in deploying the LIDAR sensor for OIS surveys (see Table 4.1). The following alternatives describe preferred and optional approaches, all accepted by FAA/NGS. Note: In Table 4.1 for true sensor-fusion-based methods, the distinction between "photo-assisted LIDAR workflow" and "LIDAR-assisted photogrammetric workflow" becomes somewhat ambiguous. However, for purposes of this document, the determining factor in distinguishing between these two types of workflows is which sensor the Contractor certifies as the "primary" source of obstruction information. A. MULTI-LOOK GEOMETRY - It is recommended that the LIDAR data be collected using two look angles (nadir and 20 forward). This approach can be met either with a custom dual-look system (i.e., a LIDAR system designed specifically for obstruction surveying utilizing dual lasers, each with a different look angle) or by using a variable-tilt sensor mount (Figure 4.1) and flying the project area twice: once in each configuration. Using two different collection geometries is important for the following reasons: 1. The nadir-pointing and tilted sensors complement each other in that the tilted sensor provides better geometry (laser points that "walk up" the face of a vertical object), while the nadir-pointing sensor yields higher return signal strength from small obstructions. 2. The dual-look approach assists in distinguishing between "false returns" (i.e., unwanted returns caused by atmospheric particles, birds, electronic noise, etc.) and real features (e.g., the top of a power pole) in that it is unlikely that the same false point would be registered with both geometries. 3. The dual-look LIDAR survey approach enhances vertical point spacing. A-6

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Figure 4.1 Example of a variable-tilt sensor mount. One method of achieving the dual-look approach is to fly the project area twice (once in each configuration) using a variable-tilt mount The enhanced obstruction detection geometry afforded by this LIDAR acquisition approach allows the imagery requirements to be slightly "relaxed" (see Table 4.1). Table 4.1 Options for deploying nadir or tilted sensors LIDAR Option System Description General Workflow Description Multi-look via tilted Deploy either simultaneous twin-look Photo-assisted LIDAR workflow. sensor sensor or tilt-mount and fly two sets of Proceed with OIS analysis steps as passes at nadir and at 20 suggested in Figure 14.1. Cross/tie lines at end(s) of each runway(s) Relaxed imagery requirements Multi-look via First set of passes parallel to runways Photo-assisted LIDAR workflow. redundant, Second set of passes perpendicular to Proceed with OIS analysis steps as orthogonal passes first set suggested in Figure 14.1. Relaxed imagery requirements Single-look, relying First set of passes parallel to runways LIDAR-assisted photogrammetric primarily on Cross/tie lines at end(s) of each workflow. Introduce image data photogrammetric runway(s) earlier in workflow. Rely methods for Stringent imagery requirements principally on photogrammetric obstruction detection methods to detect vertical obstructions (VOs), LIDAR is used to supplement processing and for DEM and orthophoto generation. B. ALTERNATIVES TO DEPLOYING MULTI-LOOK LIDAR SYSTEM 1. ALTERNATIVE #1 - The Contractor shall fly parallel flight lines (with 50% swath overlap) in opposing directions (reciprocal headings), then fly perpendicular flight lines, again with 50% swath overlap in an alternating heading pattern, covering the entire OIS. This will ensure redundant, multi-look coverage comparable to, although slightly less desirable than, a tilted sensor deployment. In this case, camera imagery with "relaxed" resolution (as compared with Alternative #2) up to 0.50 m may be used to satisfy the imagery requirement in Sections 11 and 14. A-7

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2. ALTERNATIVE #2 - The Contractor shall fly parallel flight lines (with 50% swath overlap) in opposing directions (reciprocal headings). At least one cross/tie line shall be flown over each end of each runway/approach (e.g. airport with two runways will have four cross/tie lines). The lack of multi-look geometry from the LIDAR will be compensated by the more stringent photogrammetric analysis of the imagery. In this case, the imagery will be utilized at a much earlier step in the post-processing workflow (prior to performing OIS analysis), so that all objects potentially missed by the LIDAR will be identified, analyzed, and attributed using the imagery. (Refer to Section 14.1, Figure 14.1.) The Contractor shall adhere to the imagery specifications outlined in AC 150/5300-17B. Additionally, imagery resolution shall be 0.10 m or better. C. MAINTENANCE Prior to commencing data acquisition, the contractor shall provide to NGS: certification that both preventive maintenance and factory calibration have been completed either in accordance with the manufacturer's scheduled intervals, or as justified by apparent lack of calibration stability, whichever interval is shorter. D. DATA COLLECTION 1. Carrier-phase L1 and L2 kinematic GPS shall be acquired and used in processing the trajectories. See Section 13 for further details. 2. The LIDAR system must acquire and output "intensity" data (i.e., data values proportional to the amplitude of each laser reflection). 3. The LIDAR system shall be capable of meeting the point spacing requirements specified in Section 5. 4. Sensor-to-GPS-antenna offset vector components ("lever arm" values) shall be determined with an absolute accuracy (1 ) of 1.0 cm or better in each component. Measurements shall be referenced to the antenna L1 phase center. The offset vector components shall be re- determined each time the sensor or aircraft GPS antenna is moved or repositioned in any way. Note: with a variable-tilt sensor mount, as shown in Figure 4.1, it is typically necessary to re- determine the sensor-to-antenna offset vector each time the sensor is tilted or for each fixed tilt setting. E. MALFUNCTIONS All LIDAR system malfunctions shall be recorded, and FAA/NGS shall be notified. A malfunction is defined as a failure anywhere in the LIDAR sensor that causes an interruption to the normal operation of the unit. Also, any malfunctions of the GPS or Inertial Measurement Unit (IMU) collection systems shall be recorded and reported. 4.2 AIRCRAFT A. PLATFORM TYPE The type of aircraft and the aircraft tail number used shall be stated on the LIDAR Flight Log and all aircraft used in the performance of this Project shall be maintained and operated in accordance with all regulations required by the FAA. Any inspections or maintenance of the aircraft which results in missed data collection shall not be considered as an excusable cause for delay. B. PORT OPENING The design of the port opening(s) in the aircraft shall be such that the field of view is unobstructed when a sensor is mounted with all its parts. The field of view, as much as possible, shall be shielded from air turbulence and from any outward flows, such as exhaust gases, oil, etc. The port opening shall not contain any type of window (including optically-flat windows). The sensor shall A-8

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have a clear view of the ground below, and no optics other than those internal to the LIDAR system and installed by the LIDAR manufacturer shall be placed in the optical path of the laser beam. This requirement is due to the fact that some attenuation of the laser radiation will occur even with coated, optically-flat windows, which could lead to non-detection of obstructions. 5 POINT SPACING The spacing of the LIDAR data points is a critical factor in the ability to detect obstructions. Both the horizontal and vertical point spacing (defined in Sections 5.1 and 5.2, respectively) shall meet the specifications contained in Table 5.1, unless otherwise stated in the project instructions. 5.1 HORIZONTAL POINT SPACING Horizontal point spacing refers to the spacing of the LIDAR points on a flat surface. Horizontal point spacing is defined along two directions: along track (i.e., in the direction of flight) and across track (i.e., perpendicular to the direction of flight). The horizontal along-track point spacing, HPSalong , is given by HPSalong = (5.1) 2fsc where is the flying speed over ground and fsc is the scan frequency. The horizontal across-track point spacing, HPSacross , is given by swath width HPSacross = (5.2) number of points per scan line 2H tan(S/2) = PRF(sc/2) where H is the flying height, S is the full scan angle, PRF is the pulse repetition frequency, and sc , is the period of the scanner (i.e., the inverse of the scan frequency). Unless otherwise stated in the project instructions, horizontal point spacing must meet the specifications contained in Table 5.1 of this document. 5.2 VERTICAL POINT SPACING Vertical point spacing is only applicable in the case of a tilted sensor. Vertical point spacing refers to the vertical distance between points from consecutive scan lines on the face of a vertical surface. Vertical point spacing, VPS, is given by VPS = sc cot(t) (5.3) Where, is the flying speed over ground, sc is the period of the scanner, and t is the tilt (or "forward look") angle. Unless otherwise stated in the project instructions, the vertical point spacing must meet the specifications contained in Table 5.1 of this document. Note: depending on the system used, achieving these point densities may require multiple passes. In this case, it is recommended that both parallel and perpendicular lines be flown, as recommended previously for the nadir-only sensor in Section 4.1. A-9

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Table 5.1 Point spacing specifications Maximum Across- Maximum Along- Maximum Vertical Corresponding Track Horizontal Track Horizontal Point Spacing (tilted Point Density Point Spacing Point Spacing Sensors only) LIDAR survey supplemented with aerial 0.18 m 0.18 m 0.50 m 30 points/m2 photography (digital or film) 6 RADIOMETRIC QUALIFICATION TEST This section describes a recommended test and proposed equipment to be developed and maintained at NOAA/NGS. At present, this equipment has not been constructed, so the responsibility for performing this test, if required, is solely that of the Contractor. The objective of the test procedures described here is to radiometrically qualify LIDAR systems for airport obstruction surveying. The outputs of this test are the maximum qualified operating height, hmax, for the system and the minimum ground sampling density, min , for that system. This test qualifies an individual, unique system, and it is not intended as a type qualification test. This test is constructed for single-beam, scanned-spot architecture, 1064nm LIDAR instruments, and any other instrument architectures proposed for use should be qualified in the spirit of this test. For example, a multi- beam LIDAR system would require a measurement for each beam in the system and the result would require flight planning based on the worst-case maximum flying height and the worst-case sample density, even if they result from different beam data elements. Instruments designed to operate at different wavelengths (e.g. 1540 nm) would require a reflectance standard with Lambertian characteristics and would require a measurement of 0 , the target reflectance, at the operating wavelength. The radiometric performance of a LIDAR system is critical in obstruction detection. Systems qualified by this test, and operated at an altitude above-ground-level (AGL) less than or equal to the maximu m operating altitude (calculated by the methodology of this section) and at a sample density greater than or equal to the minimum operating density (calculated by the methodology of this section) have a high likelihood of detecting small-diameter, low-reflectance obstructions, such as dark-colored poles and antennas. The test procedures have been designed to meet the following requirements: Provide a common reference so that the results from different manufacturers' LIDAR systems will have the same meaning. Provide a method that specifically tests the ability of the LIDAR system to detect small-diameter obstructions, such as antennas and poles. Utilize a ground-based, controlled test environment. Ensure repeatability of the results. This test will be carried out under the oversight of NOAA personnel at the proposed NOAA LIDAR Radiometric Calibration Center at Corbin, VA, unless written consent is granted by NOAA for the Contractor to perform an in-flight radiometric performance test in lieu of the test described below. The test setup is illustrated in Figure 6.1. The test target consists of a one-half inch diameter wood dowel painted with Kodak White Reflectance Coating. This coating provides a standard reflectance of nearly 100% at a 1064 nm wavelength and has Lambertian reflectance properties. A minimum of two configurations shall be tested; 1) with the LIDAR directed to its nadir position and, 2) with the LIDAR directed to the maximu m angular excursion planned for the OIS survey activity. The intention of measuring at multiple angular positions is that the internal optical characteristics of the LIDAR instrument may not allow equal radiometric efficiency at different scan angles. This test is intended to determine the minim um return signal within the planned operational angular range for the instrument under test. A-10

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For the first portion of the test, the target is placed at a known distance of R0 = 100 m and positioned such that it intercepts the transmitted beam approximately at the center of the beam. The dowel must be long enough to cross the entire beam spot diameter. Distant Beam Stop R0 Reflective Dowel x Lidar Under Test Figure 6.1 Setup for radiometric qualifications test to be performed at the NOAA LIDAR Radiometric Calibration Center at Corbin, VA. For each angular condition tested, the laser shall be fired at the test target for at least 10 seconds and the return signal shall be recorded. The minimum measured first-pulse intensity recorded during any of the angular setups shall then be scaled to correspond to the actual planned flight parameters using: 3 Is = I0 R R 0 max min 0 (6.1 ) where Is is the scaled, worst-case first-pulse intensity expected in operation, I0 is the minimum measured first-pulse intensity recorded during the test, R0 is the test range (100 m), Rmax is maximum range for the planned flight parameters, 0 is the reflectance of the standard target (1 at 1064 nm with the Kodak White Reflectance Coating), and min is the "worst-case scenario" reflectance, assume 5%. RMAX is calculated from: RMAX = hmax / cos t cos s (6.2) where hmax is the maximum flying height (AGL), t is the tilt ("forward look") angle, and s is the maximum half scan angle from the flight plan. A-11

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objects") due to ground clutter or noise and randomly distributed throughout the project area will typically be automatically eliminated in the OIS analysis step, due to not penetrating or falling outside the OIS, and the remainder can be easily removed during the image analysis steps. This inherent tolerance of conservative detection thresholds in the object extraction process is an important aspect of the workflow, since the key consideration in airport obstruction surveying is to avoid missed obstructions that could potentially jeopardize flight safety. The imagery input is critical, as the imagery provides a complementary and independent data source. For a more in-depth discussion of the workflow benefits, refer to "Improved Approach to LIDAR Airport Obstruction Surveying Using Full-Waveform Data," Journal of Surveying Engineering, Vol. 135, No. 2, pp. 72-82, Parrish and Nowak, 2009. Also, a slight variation on the workflow entails introducing the aerial imagery at an earlier step to facilitate a primarily photogrammetric approach to obstruction detection, assisted by LIDAR (see Section 4.1). Unfiltered LIDAR Run Object Point Cloud Data Detection Collate Objects Containing all Returns Algorithm Step 1 Option 2 Imagery Option 1 Attribute Objects Perform QA/QC Perform OIS Steps Analysis Step 4 Step 3 Step 2 Figure 14.1 Basic workflow diagram for data processing The OIS analysis (Step 2) shall be performed using NGS-supplied software contained in the NGS COM Surface Model Library (SML), a dynamic-link library that is compatible with Microsoft Visual Basic (VB), C++, and .NET. The library comprises dozens of functions that allow users to calculate surface penetrations, analyze features relative to specified OIS, and numerous other related tasks. NGS is responsible for updating SML as needed to reflect any changes in the definitions of the OIS (U.S. Dept. of Transportation, 2008). Each obstruction output from this workflow shall contain a latitude, longitude, NAVD 88 orthometric height, accuracy code (in accordance with FAA Order 8260.19, Flight Procedures and Airspace , U.S. Dept. of Transportation, 1993), and applicable zone information. Specific OIS requirements for each runway will be contained in the individual Project Instructions. 14.2 DATA CLEANING/FILTERING The Contractor shall avoid pre-filtering of the data . One aspect of LIDAR collection and post-processing for airport obstruction surveys that it is very different than for other end-user application (e.g., floodplain mapping) pertains to cleaning/filtering of the data. Many production workflows that are geared towards bare-earth terrain modeling involve a great deal of filtering/cleaning of LIDAR points very far up the processing chain, or even during data acquisition. For example, some service providers will apply a range gate in the air that removes all objects less than a certain distance from the aircraft. Similar types of filtering (e.g., max elevation, min intensity, max range difference, etc., etc.) are often applied in post-processing. For airport obstruction surveying, this type of cleaning is very dangerous, as it can easily lead to removing points corresponding to reflections from obstructions, in some cases causing these obstructions to be missed. Therefore, the Contractor must deliver the raw LIDAR point cloud (with absolutely no points removed either in the air or in post-processing) as one of the deliverables. Additionally, the Contractor must be extremely careful about any cleaning or filtering done during the analysis workflow A-22

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described above. In general, it is best to leave all points to be input to Step 1 from the LAS file and allow the Object Detection step to handle filtering. Any pre-cleaning/filtering performed should be explicitly described in the report. Additionally, these filtered points shall not be removed from the LAS file; instead they should be kept and attributed as "withheld" in the LAS file (classification bit encoding). 15 DATA LABELING All Hard Disk Drives shall be labeled with the project name, collection date(s), Contractor name, and disk contents. LIDAR data Hard Disk Drives shall be able to be easily matched with the corresponding LIDAR flight log(s). 16 DATA SHIPMENT AND PROCESSING 16.1 SHIPMENT The Contractor shall ship final deliverables in FAA/NGS format (on Hard Disk Drive), directly to FAA/NGS, to arrive within ten working days from the date of completion of the data processing. Copies of the LIDAR Flight Log and the raw navigation files may be made and used by the Contractor to produce and check the final deliverables. 16.2 FAA/NGS NOTIFICATION The same day as shipping, the Contractor shall notify FAA/NGS of the data shipment's contents and date of shipment by transmitting to FAA/NGS a paper or digital copy of the data transmittal letter via email or fax. 17 DELIVERABLES The following list outlines the required deliverables resulting from Airport OIS Survey work. Additional or custom deliverables may be described in individual project instructions. The Contractor is also responsible for providing all required deliverables in FAA AC 150/5300-16A, FAA AC 150/5300-17B, and FAA AC 150/5300-18B. If the Contractor finds a contradiction or redundancy, then FAA/NGS shall be notified. A. LABOR, EQUIPMENT AND SUPPLIES The Contractor shall provide logs of all labor, equipment maintenance and calibration (including aircraft and LIDAR system), supplies, and material to produce and deliver products as required under this document. Full information on a LIDAR vendor shall be provided if used as a specialized subcontractor by the SC. B. LIDAR SURVEY AND QUALITY CONTROL PLAN Prior to data acquisition, submit a proposed LIDAR Survey and Quality Control Plan which specifies the data collection parameters to be used and contain a map of the flight lines and the project coverage area, including flying height, speed over ground, scan angle, PRF, overall point density, and horizontal and vertical point spacing. FAA/NGS will review the proposed mission planning reports, normally within five business days, and will respond in writing with approval and/or comments. The Final Report shall contain map(s) showing the flight lines and boundaries of LIDAR data actually collected. C. GPS SURVEY LOCATION OF TEST APPARATUS DESCRIBED IN SECTION 8.3.3. D. LIDAR RAW DATA Submit the completed data collection raw output. E. LIDAR PRODUCTS Required products may include: LIDAR point cloud files, intensity images, attributed objects/obstructions, and other products described in AC 150/5300-17B and AC 150/5300-18B. The project instructions will specify which additional products, if any, are required. (See Section 3.1 D.) A-23

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F. IMAGERY - All imagery including orthophotos (if required in SOW and/or project instructions) shall be delivered according to the format and requirements outlined in FAA AC 150/5300-17B, specifically Sections 19-22 inclusive. G. FLIGHT REPORTS Submit the completed, original LIDAR Flight Logs with the data, and a copy directly to FAA/NGS. H. GPS/ IMU FILES The Contractor shall submit the original, raw data files and processed trajectory files directly to FAA/NGS, to arrive at FAA/NGS along with the raw data points and final products. The raw data files shall include RINEX files generated from each receiver's proprietary data files. (See sections 12.1 and 12.4.) I. AIRBORNE POSITIONING AND ORIENTATION REPORT Submit raw GPS and IMU data (in the manufacturer's format) along with the final processed GPS trajectory and post-processed IMU data. Also submit a report covering the positioning and orientation of the LIDAR. (See Section 11.5.) J. RANGE AND SCANNER ANGLE FILES The Contractor shall submit the original, raw data files directly to NGS, to arrive at NGS along with the raw data points and final products. K. GPS CHECK POINTS Submit an organized list of all GPS points used for the project as ground stations and accuracy check points. Indicate which GPS points are pre-existing ground control and which stations are new and positioned relative to the NSRS. See project instructions and Sections 3.1 C and 12.2. L. FAA/NGS SURVEY FORMS The Contractor shall prepare and submit the following FAA/NGS forms for each GPS check point and the GPS ground station(s): Visibility Obstruction Diagram, GPS Observation Log, Recovery Note or Station Description. (See Section 12.2.) M. CALIBRATION REPORTS There is no standard format for the calibration reports. However, the calibration reports shall contain, at a minimum, the following information: The date the calibration was performed. The name of the person, company, or organization responsible for performing the calibration. The methods used to perform the calibration. The final calibration parameters or corrections determined through the calibration procedures. N. SENSOR MAINTENANCE Provide maintenance history directly to FAA/NGS of the sensor to be used for acquiring LIDAR. (See Section 4.1.) O. DATA SHIPMENT See Sections 3 and 15 for instructions. P. DATA SHIPMENT REPORTING The Contractor shall notify FAA/NGS of each data shipment's contents and date of shipment by transmitting to FAA/NGS a paper or digital copy of the LIDAR Flight Log (marked "copy" at the top) and a copy of the data transmittal letter via email or facsimile. This shall be done the same day the data is shipped to the data processing contractor. (See Section 15.) Q. UNUSUAL CIRCUMSTANCES The Contractor shall also notify FAA/NGS of any unusual circumstances that occur during the performance of this project which might affect the deliverables or their quality and especially of any deviation from this project. This may be included in the weekly email required below, unless urgent. A-24

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R. DEVIATIONS FROM SOW Requests to exceed or deviate from the project instructions will be considered if written justification is provided to FAA/NGS in advance. No deviation is permitted until written approval is received from FAA/NGS. S. STATUS REPORTS The Contractor shall submit project status reports via email to the Contract Officer's Technical Representative (COTR) contacts in Section 14 every week, until the work is complete. These reports are due at NGS by 2:00 p.m. EST each Monday. These reports shall include a summary of completed data acquisition, with dates completed; data shipped, and dates; and any unusual circumstances, equipment malfunctions, and/or any disturbance of the sensor. A weekly status report is required even if no progress has been made. T. FINAL REPORT The Contractor shall supply to FAA/NGS a Final Report incorporating all of the information in this Deliverables section including, at least, the sections listed below: 1. Work performed under this contract, discuss each deliverable including: the maximum range from the ground station, the minimum swath overlap, percent of good laser returns (if available), standard deviation and residuals in GPS trajectories, and an explanation of the HARD DISK labeling; 2. Equipment used to perform this work, including hardware models and serial numbers, calibration reports, and software names and versions (include aircraft and LIDAR info); 3. Flight line map(s), and project coverage area; 4. Discussion of data quality including QA/QC procedures; 5. Ground Control Report, including a station list in table format; 6. Aircraft Navigation; 7 Airborne kinematic GPS Report, including ground stations; 8. Weather, solar altitude, and time of year; 10. Any unusual circumstances or problems, including equipment malfunctions (including those already reported); 11. Any deviations from this SOW, including those already reported; 12. Any recommendations for changes in the SOW for future work. U. PROPERTY OF DATA All original data, from the instant of acquisition, and other deliverables required through this contract including raw data and final products, are and shall remain the property of the United States Government. This includes data collection outside the project area. See specific guidelines and/or deviations in project instructions. V. OPTIONAL DELIVERABLE Georeferenced raster photo/imagery draped over a LIDAR-derived surface model and obstruction points to the Airport Sponsor, FAA, and NGS. 18 REVIEW Data and other deliverables not meeting these specifications may be rejected. A-25

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19 REFERENCES ASPRS, 2004. ASPRS LIDAR Guidelines Vertical Accuracy Reporting for LIDAR Data V1.0. American Society for Photogrammetry and Remote Sensing, Bethesda, Maryland. Flood, M. Eye Safety Concerns in Airborne LIDAR Mapping. Proceedings of the ASPRS 2001 Annual Convention, 23-27 April, St. Louis, Missouri (American Society for Photogrammetry and Remote Sensing, Bethesda, Maryland), un-paginated CD-ROM, 2001. Parrish, C.E., and R.D. Nowak, 2009. Improved Appro ach to LIDAR Airport Obstruction Surveying Using Full- Waveform Data. Journal of Surveying Engineering, Vol. 135, No. 2, pp. 72-82. Parrish, C.E., G.H. Tuell, W.E. Carter, and R.L. Shrestha, 2005. Configuring an airborne laser scanner for detecting airport obstructions. Photogrammetric Engineering & Remote Sensing, Vol. 71, No. 1. Parrish, C., J. Woolard, B. Kearse, and N. Case, 2004. Airborne LIDAR Technology for Airspace Obstruction Mapping. Earth Observation Magazine (EOM), Vol. 13, No. 4. U.S. Department of Transportation, 1993. FAA Order 8260.19, Flight Procedures and Airspace . Federal Aviation Administration, Washington, DC. U.S. Department of Transportation, 1996. FAA No. 405, Standards for Aeronautical Surveys and Related Products, Fourth Edition. Federal Aviation Administration, Washington, DC. U.S. Department of Transportation, 2007. FAA AC 150/5300-16A, General Guidance and Specifications for Aeronautical Survey Airport Imagery Acquisition and Submission to the National Geodetic Survey. Federal Aviation Administration, Washington, DC. September 15, 2007. U.S. Department of Transportation, 2008. FAA AC 150/5300-17B, General Guidance and Specifications for Aeronautical Survey Airport Imagery Acquisition and Submission to the National Geodetic Survey. Federal Aviation Administration, Washington, DC. September 29, 2008. U.S. Department of Transportation, 2009. AC 150/5300-18B, General Guidance and Specifications for Submission of Aeronautical Surveys to NGS: Field Data Collection and Geographic Information System (GIS) Standards. Federal Aviation Administration, Washington, DC. May 21, 2009. A-26

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20 TERMINOLOGY AND DEFINITION RELATED TO GROUND-BASED GPS DATA Ground-based GPS data are collected for both aerial imagery and LIDAR remote sensing projects for a variety of purposes, which, in any given project, can include any or all of the following: 1) post-processing of airborne GPS trajectories, 2) geometric sensor calibration, 3) georeferencing of remotely-sensed data, and 4) spatial accuracy assessments. For purposes of this report, the following terms and definitions related to ground-based GPS data collection are adopted: 20.1 GPS Base Station A GPS base station consists of a GPS antenna and receiver set up over a fixed location with accurately known coordinates. For directly-georeferenced airborne remote sensing projects (e.g., acquisition of LIDAR or directly-georeferenced aerial imagery), the GPS base station data are used in post-processing the airborne kinematic GPS data. Typically, NGS recommends a dedicated base station in or near the project site, although Continuously Operating Reference Stations -- CORS [see definition below] can, in some circumstances, be used in place of dedicated (i.e., project-specific) base stations. In the past, base stations were almost always set up over a survey monument (e.g., PACS, SACS, or other geodetic control point). However, NGS' Online Positioning User Service (OPUS) is increasingly being used to obtain base station coordinates, so that the base station can be set up in any safe location in or near the project site with a clear view of the sky. One issue for airport applications is that, in the western United States for airports with PACS and SACS that were included in the 2007 adjustment, an OPUS solution for an unknown ground station will not agree with the PACS, since the OPUS reference system is NAD 83 (CORS) and the PACS reference system is NAD 83 (2007). If OPUS is used in the western U.S., then HTDP [see definition below] should be used to predict the amount of change for the unknown point from NAD 83 (CORS) to NAD 83 (2007). To avoid this complication, and for other reasons explained below [see control station definition], the recommended procedure is to set up the GPS base station over the PACS or SACS for LIDAR airport surveys. Note: in many surveying applications, GPS base stations are equipped to actively broadcast differential GPS corrections to other GPS receivers either via radio modem or cellular connection to the internet. However, in airborne remote sensing for mapping applications, it is more common to post-process the airborne kinematic GPS data, rather than relying on real-time corrections broadcast from the base station. For airport LIDAR projects, the airborne GPS trajectories must be post-processed. 20.2 Ground Control Point (GCP) For purposes of this report, this term is used rather broadly to refer to an accurately-surveyed (usually with GPS), identifiable point on the ground that can be used for: (a) geometric sensor calibration, (b) georeferencing, or (c) spatial accuracy assessments. It is typically required--especially for controlling aerial imagery--that the GCPs be readily identifiable in the remotely-sensed data. For example, common GCPs for aerial imagery acquisition include sidewalk corners and paint stripes (especially, where paint stripes intersect, as in a parking lot or tennis court), the image coordinates of which can be precisely measured. Where there are no readily-identifiable features in the scene, pre-marked "panels" or "targets" can be placed in the project site and surveyed with GPS in advance of the airborne data acquisition. If these features are also identifiable in the LIDAR intensity data and have accurately-surveyed heights, in addition to horizontal coordinates, then they can simultaneously serve as GCPs for 3D imagery and LIDAR. 20.3 Control Station Control stations are permanent survey marks with precisely determined latitudes, longitudes and elevations relative to a geodetic datum. PACS and SACS are control stations established in the vicinity of an airport and tied directly to the National Spatial Reference System -- NSRS. Based on FAA guidance A-27

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documents, all aeronautical and airport engineering surveys should be referenced to the PACS and/or SACS. Over time, an airport operator will likely find that survey data collected from projects that are directly tied to the PACS and/or SACS will be much easier to relate to other survey data from other airport projects that are also tied to the PACS and/or SACS. Problems will arise when one project was tied to a CORS that has since been decommissioned, or a HARN that was destroyed by a construction project. If all projects are related to the PACS and/or SACS and those control stations were established in locations at the airport that are very unlikely to be destroyed or disturbed, then all survey projects will be able to be related to each other for a very long time. Setting up GPS base stations used for LIDAR and aerial imagery acquisition over PACS or SACS, and tying airport GCPs to the PACS and SACS, therefore ensures datum consistency for airport-specific applications. 20.4 Check Point Check points are GCPs specifically intended or used for assessing the spatial accuracy of the data. In order to ensure an independent accuracy assessment, check points should be maintained separate from other GCPs and excluded from sensor calibration and georeferencing procedures. 20.5 HTDP NGS' HTDP (Horizontal Time-Dependent Positioning) software enables users to predict horizontal displacements and/or horizontal velocities related to crustal motion in the United States and its territories. The software also enables users to update positional coordinates and/or geodetic observations to a user- specified date. HTDP supports these activities for coordinates in NAD 83, as well as in all official realizations of the International Terrestrial Reference System (ITRS), and all official realizations of the World Geodetic System of 1984 (WGS 84). Accordingly, HTDP may be used to transform positional coordinates between any pair of these reference frames in a manner that rigorously addresses differences in the definitions of their respective velocity fields. HTDP may also be used to transform velocities between any pair of these reference frames. [Source: National Geodetic Survey, 2008. HTDP User's Guide: http://www.ngs.noaa.gov/TOOLS/Htdp/htdpUserGuide.pdf] 20.6 CORS Continuously Operating Reference Stations (CORS) provide Global Navigation Satellite System (GNSS - GPS and GLONASS) carrier phase and code range measurements in support of three-dimensional positioning activities. NGS manages a network of CORS with data available for download via the internet: http://www.ngs.noaa.gov/CORS/. Each CORS station comprises a permanent GPS site. By using CORS as base stations [see definition above], surveyors can eliminate the need to set up their own GPS equipment at the base site, while simultaneously ensuring that their data is tied to the National Spatial Reference System (NSRS). However, as described above, for airport LIDAR surveys, it is recommended that one dedicated base station be set up over the PACS or SACS, rather than relying solely on CORS. A-28

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21 ACRONYMS AC Advisory Circular AGL Above Ground Level ANSI American National Standards Institute ASP Aeronautical Survey Program (National Geodetic Survey) ASPRS American Society of Photogrammetry and Remote Sensing COTR Contract Officer's Technical Representative CORS Continuously Operating Reference Stations FAA Federal Aviation Administration FOV Field of View GCP Ground Control Point GIS Geographic Information System GPS Global Positioning System HPS Horizontal Point Spacing HTDP Horizontal Time-Dependent Positioning IMU Inertial Measurement Unit KGPS Kinematic Global Positioning System LAS Laser Data Format LIDAR Light Detection and Ranging LRCC LIDAR Radiometric Calibration Center NAD 83 North American Datum of 1983 NAVD 88 North American Vertical Datum of 1988 NGS National Geodetic Survey NOAA National Oceanic and Atmospheric Administration NSRS National Spatial Reference System NTFS New Technology File System (for Windows NT Operating System) OIS Obstruction Identification Surface OPUS Online Positioning User System PACS Primary Airport Control Station PDOP Position Dilution of Precision POS Position Orientation System PRF Pulse Repetition Frequency RGB Red Green Blue RMSE Root Mean Squared Error SC Survey Acquisition Contractor or Survey Contractor SACS Secondary Airport Control Station SML Surface Model Library SOW Statement of Work or Scope of work UTC Coordinated Universal Time -- formerly known as Greenwich mean time (GMT) VOs Vertical Objects VPS Vertical Point Spacing A-29

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Transportation Research Board 500 Fifth Street, NW Washington, DC 20001 ISBN 978-0-309-15471-0 90000 Subscriber Category: Aviation 9 780309 154710 These digests are issued in order to increase awareness of research results emanating from projects in the Cooperative Research Programs (CRP). Persons wanting to pursue the project subject matter in greater depth should contact the CRP Staff, Transportation Research Board of the National Academies, 500 Fifth Street, NW, Washington, DC 20001. COPYRIGHT INFORMATION Authors herein are responsible for the authenticity of their materials and for obtaining written permissions from publishers or persons who own the copyright to any previously published or copyrighted material used herein. Cooperative Research Programs (CRP) grants permission to reproduce material in this publication for classroom and not-for-profit purposes. Permission is given with the understanding that none of the material will be used to imply TRB, AASHTO, FAA, FHWA, FMCSA, FTA, or Transit Development Corporation endorsement of a particular product, method, or practice. It is expected that those reproducing the material in this document for educational and not-for-profit uses will give appropriate acknowledgment of the source of any reprinted or reproduced material. For other uses of the material, request permission from CRP.