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OCR for page 49
S U RV E Y M E T H O D S 37 origin, destination, and route data are automatically col- diary and household data module. The GPS logger lected by the GPS, relieving the participant of recording receives and stores location and time data. If an individ- this information. Second, all trips are automatically ual forgets to record a trip or activity, the trip is auto- recorded, reducing potential issues with unreported matically recorded in the GPS data log. During the trips. Third, trip start and trip duration entries are auto- survey period, participants enter activity information matically recorded. Fourth, the GPS data can be used to into the GUI. The activities and trips are monitored by verify the reported trips and activities. Finally, this the GPS. The data integrity checks module detects incon- approach allows data to be downloaded from the PDAs sistencies between the information entered by the partic- in a format that can be directly used for analysis, reduc- ipant and the GPS data log. Data on the PDA is ing postprocessing data reduction costs. Possible issues downloaded through the communication module. The associated with this approach relate to potential errors data can be processed and analyzed through the use of and reliability concerns with GPS, the storage capacity GIS and other analysis tools. The system can also be pro- of PDAs, the battery life of PDAs, and the costs of PDAs. grammed to query the participant about changes in None of these issues should be major concerns. planned activities and trips. The conceptual design of the system includes two The GPS-enabled PDA system is being deployed as geographical user interfaces (GUIs), a GPS logger, a data part of a large-scale activity-travel survey in Flanders, structure, a data quality control module, a trip identifier Belgium. The results from this survey will be used in module, a geographic information system (GIS) module, other activity-based modeling and research activities. and a communication module. The modular structure The results will also be used to fine-tune the GPS-enabled allows for customization to specific applications. The PDA system and make any needed modifications. GUI contains the household and activity-based surveys. Participants enter demographic and activity-travel infor- mation in the household survey GUI at the start of the Johanna Zmud, NuStats Partners, LP, moderated this survey period. This information is stored in the activity session.