Understanding How Non-Experts Collect and Annotate Activity Data.

Training classifiers for human activity recognition systems often relies on large corpora of annotated sensor data. Crowd sourcing is one way to collect and annotate large amounts of sensor data. Crowd sourcing often depends on unskilled workers to collect and annotate the data. In this paper we explore machine learning of classifiers based on human activity data collected and annotated by non-experts. We consider the entire process starting from data collection through annotation including machine learning and ending with the final application implementation. We focus on three issues 1) can non-expert annotators overcome the technical challenges of data acquisition and annotation, 2) can they annotate reliably, and 3) to what extent might we expect their annotations to yield accurate and generalizable event classifiers. Our results suggest that non-expert users can collect video and data as well as produce annotations which are suitable for machine learning.