Inexpensive Seismic Sensors for Early Warning of Military Sentries

Small military units operate under stressful conditions with limited resources. A lightweight mobile surveillance system could reduce the effort to conduct sentry duties, and could help prevent ambushes or other types of attacks. We explore the use of built-in sensors and networking abilities of modern "smartphones" to fill this gap. Current smartphones use accelerometers to sense changes in orientation of the phone. This same capability can be used to detect vibrations in the ground produced by approaching footsteps or vehicles. We discuss the sensitivity of the phone, the filtering techniques, and the footstep signatures registered by the phone. We then discuss the possible deployment configurations of single and multiple sensors to create a sensor grid that can be networked together. Key concerns are ground noise, sensitivity of the phone, and distance between networked phones.