Citizen Sensors for SHM: Towards a Crowdsourcing Platform

Abstract

This paper presents an innovative structural health monitoring (SHM) platform in terms of how it integrates smartphone sensors, the web, and crowdsourcing. The ubiquity of smartphones has provided an opportunity to create low-cost sensor networks for SHM. Crowdsourcing has given rise to citizen initiatives becoming a vast source of inexpensive, valuable but heterogeneous data. Previously, the authors have investigated the reliability of smartphone accelerometers for vibration-based SHM. This paper takes a step further to integrate mobile sensing and web-based computing for a prospective crowdsourcing-based SHM platform. An iOS application was developed to enable citizens to measure structural vibration and upload the data to a server with smartphones. A web-based platform was developed to collect and process the data automatically and store the processed data, such as modal properties of the structure, for long-term SHM purposes. Finally, the integrated mobile and web-based platforms were tested to collect the low-amplitude ambient vibration data of a bridge structure. Possible sources of uncertainties related to citizens were investigated, including the phone location, coupling conditions, and sampling duration. The field test results showed that the vibration data acquired by smartphones operated by citizens without expertise are useful for identifying structural modal properties with high accuracy. This platform can be further developed into an automated, smart, sustainable, cost-free system for long-term monitoring of structural integrity of spatially distributed urban infrastructure. Citizen Sensors for SHM will be a novel participatory sensing platform in the way that it offers hybrid solutions to transitional crowdsourcing parameters.

eFarm: A Tool for Better Observing Agricultural Land Systems

“…Crowdsourcing and human sensing are two commonly used concepts siting at the center of citizen science [37,38]. One of the significant characteristics of citizen science is the wide coverage of participation of people from the public.…”

Biomechanically influenced mobile and participatory pedestrian data for bridge monitoring

“…26,27,31,32 Potential pedestrian postures and activities on a civil infrastructure are unlimited; therefore, only few common scenarios are tested in this study which include the following: smartphone (1) directly attached to the bridge deck surface, (2) resting in a bag on the deck, (3) in a pedestrian's pocket, and (4) in a backpack carried by a pedestrian. Table 1 summarizes the variation sources in structural vibration data extracted from pedestrians, sources of uncertainties, positive and negative extremes in sensing conditions.…”

“…Nevertheless, the modal identification results even under extreme sensor mobility match the reference operational modal analysis studies of the bridge conducted repetitively in the past. 27,31,32 The basic principle in the proposed platform is that modal parameters are sensitive to structural damage.…”

“…[23][24][25][26][27][28][29][30] Engaging citizens through ''Citizens for SHM'' (CS4SHM) for structural vibration response measurement, as proposed by the authors, opens a new avenue of sustainable sensor systems but faces significant technical challenges due to numerous uncertainties in the measurement process. 26,27 Uncertainties in the device orientation 31 as well as in the time and the space domains 32 can be eliminated by multisensory data as long as the sensor is in direct contact with the structure of interest. Yet, the usability of sensor data carried or worn by human is still of question.…”

Measuring the interstory drift of buildings by a smartphone using a feature point matching algorithm

“…The utilization of smartphones presents an excellent opportunity to decrease the cost. In recent years, smartphones have demonstrated significant applicability to SHM activities, such as road anomaly detection, pedestrian bridge vibration monitoring, cable force measurement, and dynamic characteristics of buildings . Additional SHM smartphone applications are shown in the overview of the referenced study .…”