GPS, GIS AND PERSONAL TRAVEL SURVEYS: AN EXERCISE IN VISUALISATION

In the past three years, a number of attempts have been made to use GPS devices to measure elements of person travel that have never been successfully measured by conventional interview and self-administered surveys. A key component of this application of GPS devices is to process the track points recorded, so as to produce maps and other visual representations of the travel conducted with the device. These maps and other visualisations of the travel are subsequently used in a prompted recall survey, to obtain additional data about the travel that cannot be measured by the GPS devices, such as travel purposes, number in the travelling party, and costs associated with the travel. Determining what constitutes a trip, and processing the data to produce a recognizable map of the travel is essential to the success of a prompted recall survey. In turn, the use of this type of survey avoids the need for survey subjects to enter data in a diary or electronic device during the travel – a task that is both burdensome and likely to be forgotten or omitted sufficiently often to negate most of the benefits of a GPS survey. This paper describes the use of the GPS devices in this type of survey, the paradigms used to convert the track points to coherent trips, examination and correction of the visualised travel, and presentation of the resulting maps and other visual tools to subjects in a prompted recall survey. Methods to display the trips and other information that can be gained from alternative ways of presenting the data are also outlined in the paper. These include the ability to determine when a person travels in congested conditions, examination of delays at traffic lights and other controlled intersections, and identification of the locations of acceleration and deceleration episodes.