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Table 1 Comparison of our improved measurement of physical activity in trips to existing measurement approaches

From: Combining sensor tracking with a GPS-based mobility survey to better measure physical activity in trips: public transport generates walking

Methodology Added information Applications
Global and retrospective questionnaire assessment of transport activity (trips, modes)   - Studies of residential characteristics and qualitative outcomes on mode choice
+ GPS data collection & algorithm processinga - Objective and accurate data on trips and places visited (timestamped start and end times of segments, itineraries) instead of self-reported data
- Unreliable data on transport modes
- Environmental exposures in daily path areas
- Route choice analysis
- Analyses focusing on aggregated groups of modes (e.g., motorized transport) and indicators of transport activity aggregated at the participant level (rather than trip-level information)
+ accelerometry & algorithm processinga - Objective information on physical activity in trips - Participant-level analyses of environmental exposures, transport mode profiles, and physical activity (one observation per participant)
+ GPS-based mobility surveyb - Improved accuracy through the confirmation of places visited, trips made, and modes used
- Added information on activities at places, social contacts, mood in trips, etc.
- Analyses of environments, transport modes, and physical activity disaggregated at the trip level, with reliable mode information
- Individual-level or trip-level analyses of determinants of visiting particular places (a sport facility, a fast-food restaurant, etc.) corrected from the selective daily mobility bias
- Analyses involving additional determinants, confounders, or outcomes collected at the trip level
+ spatial/temporal segmentation of trips into trip stages (algorithms + survey)c - Validated information on timestamps and locations for transitions between unimodal trip stages and transfer stages between modes - Refined analyses of transport mode used accounting for durations spent in the different modes
- Analyses of sensor-measured physical activity and personal environmental exposures (noise, air pollutants) by transport modes and during transfer stages between modes
- Calculation of exposures to geographic environments by transport modes using geographic information systems
+ manual edition of GPS itineraries (deletion and completion)c - Accurate itineraries associated with each trip stage without artefacts - Analyses of distances covered with each transport mode
- Refined calculation of exposures to geographic environments using geographic information systems
  1. aMost studies using GPS and accelerometer data in public health have reached this level
  2. bOur previous studies in the field [3, 11] have emphasized the benefits of this approach
  3. cThe aim of the present paper is to develop these last two improvements in measurement