Sensor nodes 101 are installed in the installation area A, detect displacement at each installation site, and process data. The sensor nodes 101 include a microprocessor 205 that generates self-identification information based on a combination of plural identification information included in calibration information transmitted by the calibration nodes 401, and self-identification generation information that is included in the calibration information and for identifying data processing apparatuses, respectively; nonvolatile memory 208 that retains the self-identification information; and a wireless communications unit 203 that receives the calibration information from the calibration nodes 401 and performs transmission and reception of data with an adjacent data processing apparatus 101 installed in the installation area.