Two key objectives of robot vision are autonomous navigation and mapping. Digital cameras have become relatively cheap in recent years and have appeared in a variety of consumer devices, such as PDAs (Personal Digital Assistants). It therefore makes sense to try to build systems that use vision as their primary input instead of the more traditional sonar and infrared sensors that have been used in the past. The camera can also be used for a range of other tasks. Service robots and toys typically operate in an indoor environment but rarely have a map of their environment when they are first turned on. This paper therefore addresses the problem of vision-based mapping where a camera has deliberately been chosen as the only sensor.