Table 2.
Comparison of Global Positioning System and mobile phone tracking performance and description of mobile phone tracking accuracy.
| Measures | Travel mode from travel-activity diary | ||||||||
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All | Motorcycle | Walk | Metro | Bicycle | Car | Bus | Others | |
| Tracking performance |
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| Travel diary |
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No. of trips, n | 3098 | 358 | 706 | 581 | 839 | 409 | 199 | 6 |
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Duration, minutes, mean (SD) | 28 (12) | 21 (9) | 27 (13) | 35 (11) | 26 (11) | 29 (13) | 32 (11) | 32 (11) |
| Identifiabilitya | |||||||||
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GPSb logger, n (%) | 1803 (58.2) | 280 (78.2) | 409 (57.9) | 161 (27.7) | 574 (68.4) | 257 (62.8) | 121 (60.8) | 1 (16.7) |
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Mobile phone, n (%) | 2708 (87.4) | 311 (86.9) | 623 (88.2) | 511 (88.0) | 766 (91.3) | 320 (78.2) | 172 (86.4) | 5 (83.3) |
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P value | <.001 | <.001 | <.001 | <.001 | <.001 | <.001 | <.001 | .08 |
| Traceabilityc | |||||||||
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GPS logger, median (25th-75th) | 74 (55-88) | 80 (65-94) | 74 (55-88) | 44 (36-53) | 76 (61-90) | 79 (61-89) | 74 (54-87) | 86 (86-86) |
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Mobile phone, median (25th-75th) | 76 (58-90) | 77 (60-92) | 79 (60-91) | 53 (47-62) | 85 (71-95) | 64 (46-83) | 65 (51-84) | 87 (87-87) |
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P value | .009 | .60 | .009 | <.001 | <.001 | <.001 | .05 | .32 |
| Tracking accuracyd | |||||||||
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Overall, m, median (25th-75th) | 24 (10-51) | 22 (11-47) | 21 (9-46) | 22 (11-43) | 23 (10-49) | 34 (13-76) | 25 (12-51) | 12 (4-29) |
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Satellite, m, median (25th-75th) | 22 (10-47) | 21 (10-43) | 20 (8-43) | 21 (10-40) | 22 (9-45) | 29 (11-61) | 23 (11-45) | 12 (4-28) |
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Network, m, median (25th-75th) | 97 (26-574) | 66 (22-290) | 42 (19-183) | 104 (29-609) | 69 (23-223) | 464 (80-2311) | 54 (22-372) | 177 (104-242) |
aIdentifiability of travel-activity diary trips was defined as having ≥30% of trip duration with location information.
bGPS: Global Positioning System.
cTraceability of travel-activity diary trips was quantified among the identifiable trips by the percentage of the trip duration with location information.
dTracking accuracy was quantified by the distance between the geographical coordinates of the mobile phone and the GPS tracker throughout travel-activity diary trips. This distance was calculated between concomitant geographical coordinates (geolocations with a difference in time of <10 seconds between both monitors) and corrected for time difference and traveling speed. Overall includes satellite and network locations, while satellite and network refer to the specific accuracy for each signal.