The application of LiDAR to synthetic vision system integrity

Abstract

One goal in the development of a Synthetic Vision System (SVS) is to create a system that can be certified by the Federal Aviation Administration (FAA) for use at various flight criticality levels. As part of NASA's Aviation Safety Program, Ohio University and NASA Langley have been involved in the research and development of real-time terrain database integrity monitors for SVS. Integrity monitors based on a consistency check with onboard sensors may be required if the inherent terrain database integrity is not sufficient for a particular operation. Sensors such as the radar altimeter and weather radar, which are available on most commercial aircraft, are currently being investigated for use in a real-time terrain database integrity monitor. This paper introduces the concept of using a Light Detection And Ranging (LiDAR) sensor as part of a real-time terrain database integrity monitor. A LiDAR system consists of a scanning laser ranger, an inertial measurement unit (IMU), and a Global Positioning System (GPS) receiver. Information from these three sensors can be combined to generate synthesized terrain models (profiles), which can then be compared to the stored SVS terrain model. This paper discusses an initial performance evaluation of the LiDAR-based terrain database integrity monitor using LiDAR data collected over Reno, Nevada. The paper will address the consistency checking mechanism and test statistic, sensitivity to position errors, and a comparison of the LiDAR-based integrity monitor to a radar altimeter-based integrity monitor.

Terrain Elevation Data Integrity Monitor and Referenced Navigation

“…Earlier work [2,3,5,6] has used a downward-looking radar altimeter because most aircraft are already equipped with one. The applicability of light detection and ranging (LIDAR) was investigated in [7] and forward-looking, X-band weather radar, configured in terrain mapping mode is used in [8].…”

Time Error Correction For Laser Range Scanner Data

“…The measurement errors can be broken into two categories: ranging errors and scan angle errors [9]. In our paper, we will mainly focus on time errors.…”

Feature Extraction and Separation in Airborne Laser Scanner Terrain Integrity Monitors

“…As was shown in [1], sole comparison of the vertical components of a real-time generated ALS point cloud with a LIDAR generated terrain database can lead to large, somewhat misleading errors in the presence of even small horizontal errors. The separation of features from the terrain in an ALS generated point cloud allows for processing of the terrain data separate from the feature data.…”

“…In this paper it was shown that the integrity monitoring techniques used in the radar altimeter methods did not achieve the hypothesized system performance improvements because of the apparent 'noise' introduced to the system from features with sharp gradients like building and trees [1]. This paper distinguishes itself from previous research by identifying features, such as buildings, using the information contained in the high accuracy/high density ALS point cloud.…”

“…At the 2003 DASC, Ohio University first explored the use of an ALS based system to provide the terrain database integrity monitor function [1]. In this paper it was shown that the integrity monitoring techniques used in the radar altimeter methods did not achieve the hypothesized system performance improvements because of the apparent 'noise' introduced to the system from features with sharp gradients like building and trees [1].…”