Localisation is one of the most important issues in wireless sensor networks, because the location information is typically useful for coverage, deployment, routing, location service, target tracking and rescue operations in wireless sensor networks. The localisation protocols are classified into two categories: range-based protocol and range-free protocol. The range-based protocols employ distance or angle estimation techniques to achieve fine accuracy, which require the use of expensive hardwares. On the other hand, the range-free techniques depend on the contents of received messages to support coarse accuracy. This study describes mobile anchor positioning, a range-free localisation method, which makes use of the beacon packets of mobile anchor and the location packets of neighbour nodes to calculate the location of the nodes. The anchor node, which is equipped with global positioning system, broadcasts its coordinates to the sensor nodes as it moves through the network. As the sensor nodes collect enough beacons, they are able to calculate their locations locally.

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