Pseudolites or pseudo-satellites are an emerging technology with the potential of enabling satellite navigation indoors. This technology found several applications that are not limited to indoor navigation. Precise landing, emergency services in difficult environments and precise positioning and machine control are few examples where pseudolite technology can be employed. Despite the great potential of this technology, severe interference problems with existing GNSS service scan arise. The problem can be particularly severe when considering non-participating receivers, i.e., legacy devices not designed for pseudolite signals. The design of pseudolite signals is thus a complex problem that has to account for market requirements (modifications of existing receivers for enabling he use of pseudolite signals, measurement accuracy, target application), regulatory aspects (frequency bands to be allocated for pseudolite services) and interference problems.
Pseudo-satellites, ground-based substitutes used when signals from real satellites are not available, can deliver accurate positioning information in places where conventional solutions fail. This was demonstrated on 27 June in Helsinki harbour as part of a project supported by ESA. For geographical or technical reasons, satellite positioning signals are not always available. Northern regions such as Finland, with their low angleof-view to geostationary satellites and reduced GPS coverage, suffer particularly with this problem. The solution is to set up a system with two or three pseudo-satellites, more commonly referred to as pseudolites, installed in elevated locations. The pseudolites achieve the same result as satellites in orbit, transmitting data sent by the European Geostationary Navigation Overlay Service (EGNOS) network and its data access system.