Monitoring system and synchronization method

A monitoring system comprising:

• a plurality of sensor nodes installed on a structure and configured to measure physical quantities of the structure;
• a gateway apparatus communicably connected to the plurality of sensor nodes via a wireless network;
• and
• an analysis server connected to the gateway apparatus via a network,
• the gateway apparatus including
• synchronization packet transmission unit configured to transmit a synchronization packet specifying synchronization time and measurement start time, to the plurality of sensor nodes by broadcast communication,
• each of the plurality of sensor nodes including:
• synchronization unit configured to synchronize time in the sensor node with the synchronization time indicated in the received synchronization packet;
• difference calculation unit configured to calculate a time synchronization difference which is a difference between the synchronization time indicated in the received synchronization packet and the time in the sensor node before the synchronization;
• measurement unit configured to start measurement of the physical quantities at the measurement start time of the synchronization packet;
• and
• correction information transmission unit configured to transmit the time synchronization difference calculated by the difference calculation unit and a measured value measured by the measurement unit to the analysis server,
• wherein the analysis server includes correction unit configured to correct the measured value based on the time synchronization difference, for each sensor node.

A synchronization method of a monitoring apparatus, the monitoring apparatus comprising:

• a plurality of sensor nodes installed on a structure and configured to measure physical quantities of the structure;
• and
• a gateway apparatus communicably connected to the plurality of sensor nodes via a wireless network, wherein
• the gateway apparatus transmits a synchronization packet specifying synchronization time and measurement start time, to the plurality of sensor nodes by broadcast communication,
• each of the plurality of sensor nodes
• synchronizes time in the sensor node with the synchronization time indicated in the received synchronization packet,
• calculates a time synchronization difference which is a difference between the synchronization time indicated in the received synchronization packet and the time in the sensor node before the synchronization,
• starts measurement of the physical quantities at the measurement start time of the synchronization packet, and
• transmits the time synchronization difference and the measured value obtained by the measurement to the gateway apparatus, and
• the gateway apparatus corrects the measured value based on the time synchronization difference, for each sensor node.