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Deducing Mode and Purpose Deducing Mode and Purpose from GPS Datafrom GPS Data
Peter Stopher, Jun Zhang Peter Stopher, Jun Zhang and Eoin Cliffordand Eoin Clifford
Institute of Transport and Logistics Institute of Transport and Logistics StudiesStudies
The University of SydneyThe University of Sydneyand Camden FitzGeraldand Camden FitzGerald
Parson Brinkerhoff, SydneyParson Brinkerhoff, SydneyApril 2007April 2007
April 2007 Deducing Mode and Purpose from GPS Data -- Case Studies
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IntroductionIntroduction
Increasing use of and interest in GPS devices to measure travel
Used primarily to validate standard diary surveys
Also used in Australia to evaluate VTBC interventions
Recent developments have produced small and lightweight personal devices that are very sensitive
April 2007 Deducing Mode and Purpose from GPS Data -- Case Studies
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IntroductionIntroduction
GPS collects accurate data on:Location at each instantTime at each instantSpeed of movement at each instantHeadingData quality measures
Data can be collected as often as every second or as long as desired
April 2007 Deducing Mode and Purpose from GPS Data -- Case Studies
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IntroductionIntroduction
For transport planning applications:Logging devices are all that is
requiredTransmission in real time is not
advantageous and may be expensive
4-8 Mb of on-board memory will collect second-by-second data for 1-3 months
April 2007 Deducing Mode and Purpose from GPS Data -- Case Studies
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IntroductionIntroduction
To substitute for conventional surveys, additional data are needed:Mode of travelPurpose of travel
GPS cannot collect theseWith certain supplemental data,
these can be determined
Mode and Purpose Identification
April 2007 Deducing Mode and Purpose from GPS Data -- Case Studies
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Supplemental Data Supplemental Data RequirementsRequirements
For mode:GIS of the street networkGIS of all public transport routes
(including rail and subway lines)For purpose:
Locations used frequently by household members
A GIS of the land use at the parcel level
April 2007 Deducing Mode and Purpose from GPS Data -- Case Studies
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Frequently Visited Frequently Visited LocationsLocations
Our surveys collect:Address of each workplace for each
household memberAddress of each educational
establishment attended by a household member
Two most frequently-used grocery storesHome address is known already
These locations are all then geocoded
April 2007 Deducing Mode and Purpose from GPS Data -- Case Studies
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Preliminary StepsPreliminary Steps
Assumes that the data have been subdivided into trips
We define a trip end as occurring whenever the device is stationary for more than 120 seconds
Visual inspection is also used to cross-check and correct some trip ends
About 5 percent of identified trip ends are just traffic stops
About 5 percent of actual trip ends are shorter than 120 seconds and not identified by software
Mode Identification
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Mode IdentificationMode Identification
Proceeds in a hierarchical process: Identify walk trips first – based on
maximum speed Identify rail, ferry, and other off-network
modes next – determined by location of path
Identify bus trips next – based on maximum speed and acceleration and beginning and ending on a bus route
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Mode IdentificationMode Identification
Identify bicycle trips next – household must have bicycles availableIf bicycle is available:
Check maximum speed and acceleration
Check that trip origin is home or is a location to which bicycle has already been used
If all of these are acceptable, then trip is allocated to bicycle
April 2007 Deducing Mode and Purpose from GPS Data -- Case Studies
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Mode IdentificationMode Identification
Remaining trips should be carCheck maximum speed and accelerationCheck that travel remains on the roadway
network If these check out, then trip is car,
probably driverCheck to see if origin is home or car
was used previously to reach the origin If not, and car is still identified, classify
as car passenger
Trip Purpose
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Trip PurposeTrip Purpose
Examine trip end locations and check against frequently-used locations
Following purposes should be evident: Home-based work Home-based school Some home-based shop Non-home-based work Non-home-based school Non-home-based shop (some)
April 2007 Deducing Mode and Purpose from GPS Data -- Case Studies
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Trip PurposeTrip PurposeTrip List (n)
End Points (n+1)
Private Level
Home AddressWork Address
Education AddressShopping Address
…
Public Level
Shopping CentreEducation InstitutesCommercial Places
Residence Area…
Link Match (Geocoded)
To Private LevelDestination
Link Match (Geocoded)
To Public LevelDestinations (>1)
To Public LevelDestination (Best)
FAIL
Trip PurposeExplanation
* search radius: 200 meters
April 2007 Deducing Mode and Purpose from GPS Data -- Case Studies
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Trip PurposeTrip Purpose
30 percent of trips are usually home-based work/school
13 percent of trips are home-based shop About 5-10 percent of trips are non-
home-based work, school or shop About 70 percent of trips are home-
based This process identifies about 50 percent
of trip purposes completely About 35 percent will have either origin
or destination purpose identified
April 2007 Deducing Mode and Purpose from GPS Data -- Case Studies
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Trip PurposeTrip Purpose
Remaining trips are examined with respect to:Duration of stop
Frequency of visits in GPS period
Nature of land use at the trip ends
These provide further identification of about 35-40 percent of other trip end purposes
April 2007 Deducing Mode and Purpose from GPS Data -- Case Studies
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Trip PurposeTrip Purpose
Problems are:Multi-use parcelsShopping centres – people may
Use personal servicesEat a mealShopVisit medical facilities
If the purposes are to be split to HBW, HBSchool, HBOther, and NHB – no problem
April 2007 Deducing Mode and Purpose from GPS Data -- Case Studies
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ExampleExample
The following slides provide an example of the processing steps
GPS data are collected by having respondents carry GPS devices with them for a period of time
Devices are retruned to us and the data are downloaded
April 2007 Deducing Mode and Purpose from GPS Data -- Case Studies
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Data File from GPS Data File from GPS DeviceDevice
Data are stored as binary in the device
Data are downloaded and converted to .csv file using software
Information is stored with filename which includes deployment information
Gives us information on position, time, heading, speed etc for each data point
V,07/03/2006,12:58:49,138.509622,-34.843843,500,78,3,3,8.3V,07/03/2006,12:58:51,138.509650,-34.843825,500,77,3,3,8.3V,07/03/2006,12:58:53,138.509686,-34.843809,500,65,2,3,8.3V,07/03/2006,12:58:55,138.509714,-34.843786,500,66,3,3,8.3V,07/03/2006,12:58:57,138.509732,-34.843779,500,68,2,3,8.3A,07/03/2006,12:59:00,138.509741,-34.843580,500,26,8,4,11.6A,07/03/2006,12:59:02,138.509778,-34.843454,500,34,3,4,11.6A,07/03/2006,12:59:04,138.509805,-34.843373,500,53,3,4,11.6A,07/03/2006,12:59:06,138.509824,-34.843316,500,53,3,4,11.5A,07/03/2006,12:59:08,138.509833,-34.843252,500,28,4,4,11.5A,07/03/2006,12:59:11,138.509879,-34.843183,500,30,2,4,11.5A,07/03/2006,12:59:14,138.509943,-34.843149,500,38,2,4,11.4A,07/03/2006,12:59:16,138.509970,-34.843126,500,56,4,4,11.4A,07/03/2006,12:59:18,138.510016,-34.843098,499,63,4,4,11.4A,07/03/2006,12:59:20,138.510007,-34.843115,499,72,3,4,11.4A,07/03/2006,12:59:22,138.510007,-34.843115,499,77,4,4,11.3A,07/03/2006,12:59:25,138.509970,-34.843149,498,82,2,4,11.3A,07/03/2006,12:59:30,138.509961,-34.843172,498,84,2,4,11.3A,07/03/2006,12:59:32,138.509989,-34.843176,497,86,2,4,11.2A,07/03/2006,12:59:34,138.509970,-34.843188,497,89,2,4,11.2A,07/03/2006,12:59:37,138.509961,-34.843199,496,93,2,4,11.2A,07/03/2006,12:59:39,138.509970,-34.843202,496,75,3,4,11.1A,07/03/2006,12:59:41,138.509961,-34.843206,495,73,3,4,11.1A,07/03/2006,12:59:45,138.509925,-34.843222,494,76,2,4,11.1A,07/03/2006,12:59:54,138.509833,-34.843337,492,95,2,4,11.0A,07/03/2006,12:59:57,138.509824,-34.843373,491,107,2,4,11.0A,07/03/2006,12:59:59,138.509833,-34.843390,491,110,2,4,10.9A,07/03/2006,13:00:01,138.509870,-34.843390,490,109,2,4,10.9
April 2007 Deducing Mode and Purpose from GPS Data -- Case Studies
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GPS Data Processing GPS Data Processing ProcedureProcedure
Pre-processing Trip Identification Mode Detection Purpose Detection
GPS Data
Base Map
Trip Identification
Trip Validation
Trip Manual Checking
General Mode Detect
Public Mode Detect
Public Transport Network
Household Addresses List
Public Places List
Position Matching &Purpose Detect
Convert Format
GPS Record Validation Trip List
Trip Map Final Trip List
Deployment Information
April 2007 Deducing Mode and Purpose from GPS Data -- Case Studies
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Data Prior to EditingData Prior to Editing
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Post EditingPost Editing
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With Mode AddedWith Mode Added
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With Purpose AddedWith Purpose Added
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ConclusionsConclusions
Both mode and purpose can be identified from GPS recordsRequires supplemental data such as GIS
layersRequires supplemental questions on:
Bicycle availabilityAddresses of frequently-used locations
All other information is available from the GPS record
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Questions ?
• Please use the Microphone.
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