Table 1
Two approaches for incorporating GPS tracking in studies, and their implications
for investigating environmental determinants of active living and health.
The classical Public health or
Nutrition approach to GPS studies
The transportation approach to GPS
studies
How does it proceed?
– Does not systematically identify
activity places in the GPS stream
of data
– Does not survey the nature of
activities practiced at the different
places (often only the location of
the residence and workplace/school
is known)
– Usually does not assess the
transportation modes used for
each trip
– Determines the number of steps
walked, the intensity of physical
activity, and energy expenditure
based on accelerometry
– Relies on automated algorithms to
identify activity places
– Surveys the nature of activities
(with start and end times) practiced
over the follow-up period (or a
part of it)
– Surveys the transportation modes
used for each trip over the followup
period (or a part of it)
– Usually does not rely on
accelerometry
What are the consequences for the study of environmental determinants of active
living and health?
– Determines environmental
exposures based on all GPS
locations, irrespective of activities
– Estimates associations that are
vulnerable to selective daily
mobility biases
– Investigates the correlates of the
number of steps walked, activity
intensity, and energy expenditure
(accelerometry) but lacks precise
information on the time spent in
the different transportation modes
– Would enable filtering activity
places and related trips based on
the nature of activities
– Offers the opportunity to mitigate
selective daily mobility biases
– Investigates the correlates of time
spent in the different transportation
modes but would need
accelerometry to establish a
connection with physical activity
and energy expenditure