Deducing Mode and Purpose from GPS Data

1
Deducing Mode and Purpose from GPS Data

• Peter Stopher, Jun Zhang
• and Eoin Clifford
• Institute of Transport and Logistics Studies
• The University of Sydney
• and Camden FitzGerald
• Parson Brinkerhoff, Sydney
• April 2007

2
Introduction

• 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

3
Introduction

• GPS collects accurate data on
• Location at each instant
• Time at each instant
• Speed of movement at each instant
• Heading
• Data quality measures
• Data can be collected as often as every second or
  as long as desired

4
Introduction

• For transport planning applications
• Logging devices are all that is required
• Transmission 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

5
Introduction

• To substitute for conventional surveys,
  additional data are needed
• Mode of travel
• Purpose of travel
• GPS cannot collect these
• With certain supplemental data, these can be
  determined

6
Mode and Purpose Identification
7
Supplemental Data Requirements

• For mode
• GIS of the street network
• GIS 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

8
Frequently Visited Locations

• Our surveys collect
• Address of each workplace for each household
  member
• Address of each educational establishment
  attended by a household member
• Two most frequently-used grocery stores
• Home address is known already
• These locations are all then geocoded

9
Preliminary 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

10
Mode Identification
11
Mode 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

12
Mode Identification

• Identify bicycle trips next household must have
  bicycles available
• If 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

13
Mode Identification

• Remaining trips should be car
• Check maximum speed and acceleration
• Check that travel remains on the roadway network
• If these check out, then trip is car, probably
  driver
• Check 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

14
Trip Purpose
15
Trip 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)

16
Trip Purpose
17
Trip 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

18
Trip 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

19
Trip Purpose

• Problems are
• Multi-use parcels
• Shopping centres people may
• Use personal services
• Eat a meal
• Shop
• Visit medical facilities
• If the purposes are to be split to HBW, HBSchool,
  HBOther, and NHB no problem

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Example

• 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 Device
V,07/03/2006,125849,138.509622,-34.843843,500,78
,3,3,8.3 V,07/03/2006,125851,138.509650,-34.8438
25,500,77,3,3,8.3 V,07/03/2006,125853,138.509686
,-34.843809,500,65,2,3,8.3 V,07/03/2006,125855,1
38.509714,-34.843786,500,66,3,3,8.3 V,07/03/2006,1
25857,138.509732,-34.843779,500,68,2,3,8.3 A,07/
03/2006,125900,138.509741,-34.843580,500,26,8,4,
11.6 A,07/03/2006,125902,138.509778,-34.843454,5
00,34,3,4,11.6 A,07/03/2006,125904,138.509805,-3
4.843373,500,53,3,4,11.6 A,07/03/2006,125906,138
.509824,-34.843316,500,53,3,4,11.5 A,07/03/2006,12
5908,138.509833,-34.843252,500,28,4,4,11.5 A,07/
03/2006,125911,138.509879,-34.843183,500,30,2,4,
11.5 A,07/03/2006,125914,138.509943,-34.843149,5
00,38,2,4,11.4 A,07/03/2006,125916,138.509970,-3
4.843126,500,56,4,4,11.4 A,07/03/2006,125918,138
.510016,-34.843098,499,63,4,4,11.4 A,07/03/2006,12
5920,138.510007,-34.843115,499,72,3,4,11.4 A,07/
03/2006,125922,138.510007,-34.843115,499,77,4,4,
11.3 A,07/03/2006,125925,138.509970,-34.843149,4
98,82,2,4,11.3 A,07/03/2006,125930,138.509961,-3
4.843172,498,84,2,4,11.3 A,07/03/2006,125932,138
.509989,-34.843176,497,86,2,4,11.2 A,07/03/2006,12
5934,138.509970,-34.843188,497,89,2,4,11.2 A,07/
03/2006,125937,138.509961,-34.843199,496,93,2,4,
11.2 A,07/03/2006,125939,138.509970,-34.843202,4
96,75,3,4,11.1 A,07/03/2006,125941,138.509961,-3
4.843206,495,73,3,4,11.1 A,07/03/2006,125945,138
.509925,-34.843222,494,76,2,4,11.1 A,07/03/2006,12
5954,138.509833,-34.843337,492,95,2,4,11.0 A,07/
03/2006,125957,138.509824,-34.843373,491,107,2,4
,11.0 A,07/03/2006,125959,138.509833,-34.843390,
491,110,2,4,10.9 A,07/03/2006,130001,138.509870,
-34.843390,490,109,2,4,10.9

• 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

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GPS Data Processing Procedure
Pre-processing Trip Identification Mode
Detection Purpose Detection
GPS Data
Trip Identification
General Mode Detect
Household Addresses List
Trip Validation
Deployment Information
Public Transport Network
Public Places List
Trip Manual Checking
Convert Format
GPS Record Validation
Trip List
Position Matching Purpose Detect
Public Mode Detect
Base Map
Trip Map
Final Trip List
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Data Prior to Editing
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Post Editing
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With Mode Added
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With Purpose Added
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Conclusions

• Both mode and purpose can be identified from GPS
  records
• Requires supplemental data such as GIS layers
• Requires supplemental questions on
• Bicycle availability
• Addresses of frequently-used locations
• All other information is available from the GPS
  record

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Questions ?

• Please use the Microphone.