Initialisation for Visual Tracking in Urban Environments

Outdoor augmented reality systems often rely on GPS to cover large environments. Visual tracking approaches can provide more accurate location estimates but typically require a manual initialisation procedure. This paper describes the combination of both techniques to create an accurate localisation system that does not require any additional input for (re-)initialisation. The 2D GPS position together with average user height is used as an initial estimate for the visual tracking. The large gap in available GPS accuracy versus required accuracy for initialisation is overcome through a search procedure that tries to minimise search time by improving the likelihood of finding the correct estimate early. Re-initialisation of the visual tracking system after catastrophic failures is further improved by modelling the GPS error with a Gaussian process to provide a better estimate of the current location, thereby decreasing search time.