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Wireless sensor networks (WSNs) are extensively used in military applications for border area monitoring, battle-field surveillance, tracking enemy troops, where the sensor nodes run on battery power. Localisation of sensor nodes is extremely important to identify the location of event in military applications for further actions. Existing localisation algorithms consume more energy by heavy computation and communication overheads. The objective of the proposed research is to increase the lifetime of the military sensor networks by reducing the power consumption in each sensor node during localisation. For the state-of-the-art, we propose a novel intelligent unmanned aerial vehicle anchor node (IUAN) with an intelligent arc selection (IAS)-based centralised localisation algorithm, which removes computation cost and reduces communication cost at every sensor node. The IUAN collects the signal strength, distance data from sensor nodes and the central control station (CCS) computes the position of sensor nodes using IAS algorithm. Our approach significantly removes computation cost and reduces communication cost at each sensor node during localisation, thereby radically extends the lifetime and localisation coverage of the military sensor networks. Defence Science Journal, Vol. 64, No. 6, November 2014, pp. 557-563, DOI : 10.14429/dsj.64.5295  2014, DESIDOC DEF. SCI. J., VOL. 64, NO. 6, NOVEMbER 2014 558 UAVs to carry positioning device and transmitter to localise the sensor nodes. Yadav 17 , et al. explained the localisation using global positioning system (GPS)-enabled flying anchor nodes. Vincent 18 , et al. employ the UAVs to distribute the energy burden across the WSN. Our main idea was to collect the location and distance data from the sensor nodes and compute their locations at (CCS). In our approach, UAV was empowered with intelligence and utilised as flying anchor node. This is referred as IUAN and its novel design is shown in Fig.1.The IUAN authenticates the SIDs in the VQ using the Db SID as Db SID contains valid sensor id numbers. The invalid SIDs are ignored and LD messages are constructed for only the valid sensor nodes. The Db SSD is used to withstand with radio irregularity. The signal strength at the locations around the transmission range of a sensor node varies with the distance and environmental effects. The path loss effect causes the radio signal to attenuate variously in different directions. The proposed work assumes the radio irregularity model (RIM) explained by Zhou 19, et al. The Table 2 shows the structure of Db SSD with sample values of the Signal Strengths (SSs) at 3.048 m away from the mica2 mote in four directions. The SS is calculated based on signal strength-distance relation using received signal strength indication (RSSI) measurements with the knowledge of degree of irregularity (DOI). The IUAN contains IUAN control unit (ICU), sensor ID database (Db SID ), visitor queue (VQ), signal strength-distance database (Db SSD ), IUAN location database (Db ILOC ) and location...

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