An autonomous location-tracking ability is a major performance for locating sensor systems to navigate an autonomous mobile robot. This paper presents a vision-based omnidirectional location sensor system we have developed in our lab. It is composed of active landmarks

a vision sensor

an image and data processing device. The whole sensor system can be mounted on a mobile robot. Meanwhile

the relative calculation methods and function software were developed that used to obtain the absolute position and orientation of the sensor system and vehicles in their working places. The experiments showed this system could get its pose online and suitable position accuracy for track guidance of mobile robots as well.