Integrity Monitoring of Digital Elevation Models for Synthetic Vision Systems Using Approximate Graph Matching Techniques and X-Band Weather Radar Measurements

Synthetic Vision Systems (SVS) provides general aviation pilots with displays of stored geo-spatial data representing terrain, obstacles, and cultural features, which have the potential to improve flight safety by providing situational awareness and reducing the likelihood of Controlled Flight into Terrain (CFIT). This paper describes an integrity monitor which uses a novel approach to check the consistency between a terrain elevation profile synthesized from X-Band weather radar sensor information and the profile given in a Digital Elevation Model (DEM). Both profiles are first converted to a graph based representation, where key points of interest are extrapolated and the spatial relationship between them stored in a hierarchical graph. A real-time comparison is then made through error-correcting graph isomorphism techniques which are highly tolerant of error due to scaling, rotation and deformation. Flight-testing data from NASA’s AvSP is used to validate the proposed monitor approach. Initial results of this assessment are presented.