Observing outdoor activity using global positioning system-enabled cell phones

Abstract

Global positioning system (GPS) technology offers a methodological advance over existing methods of assessing exposure to social and built environments in health studies. The usefulness of GPS-enabled cell phones with open-source software to track users in real-life situations was assessed by carrying phones through three standardized loops in Portland, Oregon. Overall, the cell phones recorded position in 62.8% of tests. Position acquisition varied by the environment in which the cell phone was carried, highest in open areas (83.5%) and lowest under cover (37.5%). The ability of the cell phones to track varied by mode of transportation. Tracking performance was adequate when moving by car (46.6%) or on foot (29.9%), but low on public transportation (3.8%). The GPS-enabled cell phone system showed adequate reliability under typical study conditions to track outdoor activity. Systems built on consumer electronics offer inexpensive and reliable technology for clinical/epidemiological location-based studies. © 2008 Springer-Verlag Berlin Heidelberg.