Deducing Mode and Purpose from GPS Data Peter Stopher, Jun Zhang and Eoin Clifford Institute of...

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


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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


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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


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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


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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


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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


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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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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


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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)


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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


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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


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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


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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


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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


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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


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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


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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.

Deducing Mode and Purpose from GPS Data Peter Stopher, Jun Zhang and Eoin Clifford Institute of...

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