Everything in Place

Geographic information systems (GIS) — merging cartography, statistical analysis and database access — have existed for about 50 years, but their role in aviation safety soon will take a few leaps forward, experts told a December 2012 forum hosted by the U.S. National Transportation Safety Board (NTSB).

Concepts involved often are analogous to those in highway safety (such as intelligent routing of trucks carrying hazardous materials and smartphone apps for motor vehicle collision avoidance), infrastructure analysis, pipeline safety and positive train control. Impediments to expanded GIS uses in aviation safety, however, could include misinformed safety conservatism or delays within this transportation mode in recognizing the opportunities at hand, some presenters said.

Enabling Aircraft Containment

Since the aviation industry cannot invent more airspace to satisfy its demands, the alternative is containment — reducing the space from aircraft to aircraft — and this became the basis of 21st-century air traffic management (ATM) systems, said Dejan Damjanovic, director, air and marine solutions, of GeoEye. Containment, however, entails critical safety concerns with respect to obstacles and the part that GIS plays, he said, adding, “If we are going to be flying more airplanes in the same cubic miles of airspace, we need to have a much better handle on how [GIS] information is acquired and maintained.

“The primary notion is message-based ATM with smaller containment to get, purely and simply, more airplanes per hour in and out of everyone’s airspace and airports in order to improve travel, improve efficiencies and, of course, enhance safety at the same time. One of the predominant requirements … is that we must have a concise and clear idea of where are the terrain and the obstacles that affect flight, because fundamentally we will be bringing aircraft closer and closer to terrain and obstacles in order to increase the numbers [of aircraft] in a given [volume] of airspace. … The data standard [Eurocontrol Aeronautical Information Exchange (AIX)] … provides for an aeronautical information foundation that allows us to always come up with the same aeronautical answer … the exact same levels of quality and the same levels of accuracy.”

GIS addresses absolute accuracy — where are you in the world — and relative accuracy, such as correctly depicting distance on a digital map from one part of a runway to another part, or from an obstacle to a runway or between runway centerlines within the same airport. “So relative accuracy is as important as absolute accuracy; both need to coexist within the same frame of reference,” Damjanovic said. Key documents created to accomplish this are International Civil Aviation Organization (ICAO) Annex 15, Aeronautical Information Services, which defines how aeronautical information is collected, and the ICAO Performance Based Navigation Manual.

GIS data collection methods most relevant to aviation are aerial photography, U.S. National Aeronautics and Space Administration (NASA) Space Shuttle imagery, satellite imagery and light-detection and ranging (lidar) on ground and airborne platforms. He cited examples from GeoEye’s work at San Diego International Airport.

“We’re coming up with literally thousands of points around a single runway at San Diego — 2,700 points per runway — an astonishingly large number,” he said. “[For] power lines and fences, we come up with close to 500 just for a single runway. … Polygonal obstacles — typically man-made buildings — are the most significant challenge. … We identified over 3,000 individual buildings or man-made structures off that one [San Diego] runway. In ballpark numbers, it’s not uncommon in populated areas in the United States to identify between 5,000 and 10,000 obstacles around a single runway. … It’s going to be even more critical in the NextGen [U.S. Next Generation Air Transportation System] future that we have an incredibly detailed and complete grasp of all the point features, the line features and the polygon features that constitute the obstacles around given airports. … You must have a prudent and well-thought-through plan … because you need to collect [and validate the data] — and maintain it forever.”

Safety Research Directions

Safety-related aviation analyses are inherently spatial, yet individual aviation professionals tend to work in different, limited topological frameworks, said Christopher Knouss, a geospatial computing specialist at MITRE Corp. “One of the things that I’ve discovered along the way [is] a lot of the individuals associated with the airspace or … procedures or … traffic have never actually seen [these] on a map,” he said. “They don’t understand what the relationships between some of the different airspaces are — surrounding airspace, special activity airspace — so [appreciating that] is often the first step. We will also take a look at some of the safety aspects” using maps. MITRE specialists, for example, will present runway excursion data and cases within a GIS and radar coverage context, he said.

However, efforts to conduct analyses combining GIS data and flight operational quality assurance data sometimes run into incompatibilities. “The simulation folks are using that data, but … having to convert it again into the modeling environment … then others who want to do additional data-mining are doing conversion after conversion of the same data, which introduces resolution error, biases and inaccuracies,” Knouss said.

ICAO’s GIS Applications

Calculating global air carrier accident rates with state or region rates, then using maps to compare local rates with air traffic data for the associated flight information region, provides fresh perspectives on safety risks, said Marco Merens, technical officer, ICAO Air Navigation Bureau. Sometimes, however, such comparisons have revealed that it was “unfair to create a region [from states arbitrarily],” he said, adding, “That’s actually a known problem in geography … it’s called the modifiable unit area problem, and so GIS helps us to understand that.”

ICAO’s GIS Web portal complements its secure Internet platform for iSTARS group members to exchange safety intelligence, he said. These platforms help ICAO produce an integrated safety analysis that incorporates state-level results of its Universal Safety Oversight Audit Program (USOAP).

A second use of GIS is overlaying accident sites at latitude-longitude points on a world map depicting air traffic flows. Referring to such a map, Merens explained color-coding of fatal and non-fatal events, states and intensity of activity from departures data in the selected areas. For example, the United States has about 10 million departures a year versus some Western African countries with fewer than 7,000.

“ICAO has always grouped these states by ICAO regions, and West Africa is an ICAO region,” Merens said. “Once we plotted the traffic, we [saw] that we could not have created a … more unfair [grouping of states for safety-analysis purposes] because it actually contains the lowest traffic in Africa, and [yet some states] actually have not many accidents. … A single accident in that region doubles or triples the rate, so we cannot really use it to measure state safety. So we’ve actually stopped doing that.” Instead, use of United Nations regions often yields fairer comparisons, he said.

He also cited GIS color-coding of plotted points where losses of separation have occurred, and overlaying these with hazard-mitigation symbols on recorded aircraft tracks in specific state airspace of interest, such as a flight information region.

U.S. GIS Coordination

The U.S. Government Accountability Office (GAO) in November 2012 issued a report¹ citing insufficiently coordinated collection of GIS data by the U.S. Department of Transportation (DOT), said David Cowen, chairman, National Geospatial Advisory Committee. But efforts to establish a common, interoperable GIS platform for nearly all federal agencies have made progress, he said, noting, “We have the prototypes of a geospatial platform in place now. … So you can go in and get things … common data, common services, common applications through Web-based interfaces instead of buying desktop GIS [software] and staffing up. This is the way we are going, and this provides [the aviation community] a great way to enter the [GIS] field. … A robust GIS program would enable NTSB to improve the way it monitors and manages its safety programs. NTSB should take advantage of the platform that now exists and … help guide the stakeholders.”

Also in response to the GAO report findings, Stephen Lewis, a director of GIS at DOT, said that the department is setting up a geospatial policy advisory council.

Proposed GIS-related infrastructure projects — including a three-dimensional terrain elevation program that addresses one of the major aviation risks in Alaska — would stimulate economic growth, Cowen said. “The pilots flying in Alaska are doomed in many cases,” he said. “The [GIS] data is terrible in terms of trying to find a landing strip there because elevation data is bad.”

More Accurate Elevations

GIS in the broadest sense can be “geographic information science or any spatially enabled or location-aware technology,” said Reginald Souleyrette, a transportation engineer and University of Kentucky professor representing Data and Information Systems, Transportation Research Board of the National Academies. Specialists have watched their field evolve from what they call a map-view stage to a navigation-view stage to today’s behavioral-view stage. “Transportation futurists see a world with billions of embedded sensors,” he said, and human-machine and machine-machine interaction are affected.

NTSB’s interest extends mainly to ways of using GIS to help identify trends and areas of growing risk in all transportation modes. “For example, if we start to see a series of accidents and incidents, with GIS we can identify patterns, understand relationships and use its capabilities to help develop countermeasures,” said Chairman Deborah Hersman.

For transition to NextGen and the Single European Sky ATM [Air Traffic Management] Research (SESAR) program, GIS standards such as common geography markup language for geospatial data have become crucial to safe interoperability, said Nadine Alameh, director of interoperability programs, Open Geospatial Consortium (OGC).

“A few years back, the … global aviation community agreed to adopt [AIX,] an international framework of [GIS] standards specifically for the goal of improving air travel safety and operational efficiency,” Alameh said. “Location is just so critical to all aspects of aviation that [the U.S. Federal Aviation Administration (FAA) and Eurocontrol] adopted as part of that framework the suite of OGC standards [using] the geography markup language to encode all aeronautical information.”

She said OGC activities include developing a suite of Web services for aviation to “ensure that the right users get the right information at the right time — so you don’t get everything [at once], you just get what you need.” When a runway has been closed, for example, pilots need to know immediately — not in five minutes — through advances such as digital notices to airmen, she said.

Much has been published about how satellite-based aircraft navigation and ATM enable NextGen–SESAR capabilities, but sensor technology and GIS revalidation of terrain elevations and obstacle descriptions are less well known, added Jeffrey Danielson, physical geographer, Earth Resources Observation and Science Center, U.S. Geological Survey (USGS).

Before this century, methods for measuring elevations at map locations in the continental United States presumed users’ needs of the 1960s. Now aviation safety margins can benefit from far greater data accuracy and resolution made possible by lidar, the gold standard for many GIS measurements. Most of the data going into the USGS National Elevation Dataset (NED) is based on lidar, so far representing about 28 percent of elevation data for the lower 48 states, he said.

“Lidar really is a way to map the whole vertical profile of a landscape,” Danielson said. “We’ve seen drastic improvements in the accuracy of our terrain data using lidar … to map the feature much more precisely in terms of its position as well as the actual morphology of that feature.”

The NED, envisioned 15 years ago, is a seamless raster database that functions as a layer of the official USGS continental U.S. map, with updates six times a year. Its dataset is “edge-matched with spatially referenced meta-data to know what source was used to make [each] piece of data,” he said. The NED offers multiple resolutions,² bare-earth terrain imagery, contours and extensive data from participating government agencies. The currency of the NED varies dramatically among U.S. states, however, so specialists color-code the 1960s contours separately from up-to-date, usually lidar-based, contours.

Whether mounted on an aircraft, ground vehicle or tripod, a lidar system records a point cloud comprising billions of three-dimensional mathematical coordinates as X, Y and Z points of the vertical structure scanned. “Towers are of concern for the FAA and people looking at obstacles, for example,” he said. “Using traditional totalization and GPS [global positioning system] is still your most accurate way of measuring obstacles, but lidar does have the potential to be a tool to map obstructions [for an airport] landing approach.”

Upgrading Airport Data

Because the FAA provides funding through the congressionally approved Airport Improvement Program, the agency can require the recipient U.S. airports to use the latest GIS data submission standards, said Michael McNerney, assistant manager of FAA’s Airport Engineering Division. The Airports GIS program covers about 3,300 such airports as part of the national plan of integrated airport systems, which includes 547 airports certified under Federal Aviation Regulations Part 139 standards for scheduled air service. “We are primarily developing a data collection program in GIS,” he said. “Another benefit is improved safety by having better data, real-time data, corrected and traceable data. [We are supporting] NextGen [by] embarking on a program to do full-scale geospatial data collection at engineering-level accuracies [for the certified airports during 2013 and 2014].”

The accuracy improvement enables FAA airport specialists to measure on a digital airport layout plan the distances between runways, parallel taxiways or two adjacent buildings, for instance. “By 2016, we expect to go full digital/electronic on airport layout plans and all of our digital data,” McNerney said.

The program is collecting data for more than 100 features of each airport sufficient for standards-compliant drawings. “[This has] many different layers, and has tools to measure distances among a lot of GIS tools,” he said. “One of our outputs is 1.0-ft [0.3-m] elevation contours in the airport area; our consultants that use the data think that’s one of our best products.”

McNerney said that FAA Airport GIS now collects data for airport airside and groundside operations — the movement and non-movement areas — to provide a complete geospatial picture of an airport. This is much different from discrepancies of the past.

“When I was an airport consultant and was doing the master plan for Houston Intercontinental [Airport], we were siting a new runway, and the FAA was telling us that the runway was too far away from the tower, [saying,] ‘You can’t site it there,” he recalled. “We said, ‘Yes, it’s within limits.’ And so they said, ‘Show us your data.’ When we showed them the data, they said, ‘Oh, that’s where the tower is.’ They were still using an old airport layout plan that did not have the correct tower location. [Elsewhere,] a building would be located in the general area, but [on the map] it might be … 50 ft [15 m from] where it really is. So it’s important to have everybody looking at the same data, having safety-critical data for runways and taxiways, having a very rigorous verification and validation program.”

Building Instrument Procedures

A new instrument procedure development system (IPDS), developed and deployed in the last five years, gradually is replacing a legacy system to develop procedures for U.S. and some non-U.S. flight operations under instrument flight rules (IFR), said George Gonzalez, representative of mission support services, aeronautical navigation products, technology and air traffic control products, and the IPDS at the FAA Air Traffic Organization.

FAA staff currently uses IPDS solely for space-based navigation procedures, specifically those using GPS area navigation (RNAV) and required navigation performance (RNP) levels of technology. Because different layers of data are provided using a GIS format, procedure development specialists instantly can show/hide overlay data from accurate databases for elements such as obstacles, fixes, airports, runways and navaids with colors assigned as needed.

“This new system uses [AIX] to push and pull [GIS] Web services and data; there’s just about everything a procedure specialist would need,” Gonzalez said. “[I believe IPDS will] become useful for NTSB when it comes to trying to evaluate a procedure that may or may not have been involved with an aircraft crash. … A module being delivered within the next 12 to 18 months will provide ground-based [navigation aid] procedure development. … We’re also looking at providing flight path data on this system.” The ground-based module streamlines manual processes for building diverse standard instrument departure procedures and obstacle evaluation assessments.

The system includes two-dimensional and three-dimensional views of locations. In three-dimensional view, the specialist instantly can set the viewer’s position at any direction and elevation to study terrain and obstacles. “Cylinders [drawn by IPDS show each] obstacle with its accuracy, which has to be taken into consideration when there are procedures being built because some obstacles don’t have a very exact accuracy of the height or the position [data],” Gonzalez said.

In closing, the USGS’s Danielson stressed the need for GIS data users in aviation to ask about “whatever quality assurance methods that an organization or group is using in collecting and then processing the data. … From the USGS perspective, we produce a lot of [terrain] data, and definitely the meta-data sometimes is lagging behind the data, but we’re striving to match that up with the data in terms of currency. … Meta-data probably is one of the most challenging aspects to geospatial data.” 

Notes

1. GAO. Geospatial Information: OMB [Office of Management and Budget] and Agencies Need to Make Coordination a Priority to Reduce Duplication
2. Current resolutions possible are 1 arc second, about 30 m (98 ft); 1/3 arc second, about 10 m (33 ft); and 1/9 arc second, about 3 m (10 ft). “Bare earth” refers to lidar measuring/depicting the elevations of points on the contour surface as opposed to capabilities such as “first return” from the top of a surface (such as a man-made structure) or the “top of canopy” of trees.