Integrity in urban and road environments and its use in liability critical applications

The use of integrity in the field of GNSS is usually linked to safety critical applications. This paper introduces the use of integrity in the so called liability critical applications i.e. those where undetected GNSS large position errors can generate significant legal or economic negative consequences. Unlike in civil aviation, liability critical applications are usually associated to an urban or road environment where position integrity becomes a real challenge basically derived from the effects to non-line of sight multipath. Electronic toll collection has been selected as a good example of liability critical applications and their requirements, and for analyzing how the use of integrity improves their performance. The paper focuses in a novel technique for the computation of positioning integrity in the identified environments, the so called isotropy-based protection levels, that is also believed to be a very promising technique for its application for safety critical applications and, thus, a potential contribution to the USA GNSS evolutionary architecture study (GEAS) and the EU GNSS Evolution Programme.