Implementation and evaluation of Space Time Alarm ClockMaster thesis presentation

Student: Adrian C. PrelipceanSupervisor: Takeshi ShirabeCo-supervisor: Falko Schmid

AG242X Geoinformatics

Outline

Implementation of Space Time

Alarm Clock

Evaluation of Space Time Alarm Clock

Conclusions

Introduction

Objective

Methods - Space Time Alarm

Clock

Alarm clockWhy do we use alarm clocks?1. To perform activities without worrying about the time2. To get a sense (control) of time3. To synchronize our schedule with that of others4. As a reminder5. To wake up

NavigationWhy do we use navigation systems?1. To travel from the current location to a destination2. To get directions while traveling

a. Audio directionsb. Visual directions - display the route (usually the shortest path) on a digital map

Alarm clock and navigation

Is it possible to combine the alarm clock functionality with the routing functionality - reach a destination by a deadline?

source: http://linuxhub.net/wp-content/uploads/2010/01/alarm-clock.png and http://www.roadmapgps.com/models/tomtom-go-510/scr-navigation-map-6.jpg

ObjectiveThis thesis has three objectives: 1. develop a method that measures the time it takes from any location to a destination

by following any of the possible moves from a given location2. provide the derived information to smartphones3. develop a prototype that implements this method and test its computational

performance to identify bottlenecks

MethodsThe thesis proposes a new method, called Space Time Alarm Clock, which provides two main functionalities:1. Alarm functionality - continuously tracks the user in space and time and alarms

when the user has to leave the current location to reach a destination by a deadline 2. Labeling functionality - determines the possible movement choices of a user,

computes the shortest travel time and informs the user about the consequences of his/her movement via labels

AssumptionsSpace Time Alarm Clock makes three important assumptions:1. The user moves along streets, not through buildings or open field2. The user moves at a constant speed3. The user is a pedestrian

Space Time Alarm Clock - StepsSpace Time Alarm clock performs 6 computational steps:1. Destination and deadline specification 2. Shortest travel time computation3. Location detection 4. Earliest arrival time estimation5. Consequence values computation6. Communication

Alarm functionality

Space - Time prism

Alarm functionality

Space - Time cone for a destination

Alarm functionality

Space - Time cone for an origin and a destination

Shortest travel time computation

- Computed by using Dijkstra’s Shortest Path Tree Algorithm

- each node contains the information about the shortest travel time to the destination

Location detection and map matching

- used to identify the road segment the user is on

- the locations received by the GPS are map matched in real time

- one assumption is that the user moves along streets, not through buildings or open field

source: http://graphics.stanford.edu/projects/lgl/papers/cdgnw-ammrfd-11/image.gif

Audio communication (upper left)Visual communication (lower right)

Audio communication - alert when the user is

outside the space time cone

Visual communication - display

the shortest travel time for any of

the possible movement options

Implementation - architectureGeneral steps:

1. User input

2. Send parameters to the

server

3. Server replies with the

subnetwork

4. Labels are drawn and user

is alerted

Implementation - serverThe server:● stores the data set (Open Street Map) of the study area (Stockholm)● extracts the relevant subnetwork● performs the shortest path tree algorithm on the subnetwork● sends the subnetwork, which also contains the shortest travel time from any node to

the destination, to the client

Implementation - clientThe client:● contacts the server for the subnetwork● temporarily stores (caches) the subnetwork in a local database● detects the user’s location along the subnetwork (map-matching)● draws the labels (the shortest travel time for the possible movement choices the

user can make) at the decision making points ● alarms the user when he / she should start moving towards the destination to reach

it by the deadline

Implementation

User input flow

Using STACWhere to next?

● Forward – 3 minutes and 6 seconds

to the destination

● Left – 6 minutes and 37 seconds to

the destination

● Turn around – almost 10 minutes to

the destination

Best action? The user decides

Using STACAvailable information

● Time left at the current location

● Shortest travel time to reach the

destination

● Shortest network travel distance to

reach the destination

What to do? The user decides

EvaluationUser evaluation:

● do users find STAC useful?● insufficient respondents (5 questionnaires)

Performance evaluation:● identify potential bottlenecks

Performance EvaluationProcessing time is influenced by:● Available time ● Distance between origin and destination

Performance - overall time

Influence of available time (left) Influence of distance between origin and destination (right)

Performance EvaluationOperations performed by server:● generate ellipse● get closest node to the destination● extract subnetwork within ellipse● generate shortest path tree

Operations performed by client:● read the subnetwork sent by the

server● generate network topology ● build indexing system

Bottlenecks

Identifying bottlenecks (origin corresponds with destination and available time is 3 hours)

Identified bottlenecksOperations performed by server:● generate ellipse● find closest node to the destination● extract subnetwork within ellipse● generate shortest path tree (20.2%)

Operations performed by client:● read the subnetwork sent by the

server (34.5%)● generate network topology (24.4%)● build indexing system (20.6%)

Conclusions and future work● this thesis proposed, implemented and evaluated a new method, which we entitled

Space Time Alarm Clock (STAC), for monitoring a user’s location and alerting when the user has to leave the current location to reach a specified destination by a specified deadline

● this work identified the limitations and bottlenecks of the current implementation of STAC

● to make STAC useful, future work should involve solving the current bottlenecks, making STAC available for the entire world and testing whether STAC can be extended to provide its functionality to users that are not only pedestrians

Summary

Is it possible to combine the alarm clock functionality with the routing functionality - reach a destination by a deadline?

?source: http://linuxhub.net/wp-content/uploads/2010/01/alarm-clock.png and http://www.roadmapgps.com/models/tomtom-go-510/scr-navigation-map-6.jpg

SummaryThe solved objectives:1. develop a method that measures the time it takes from any location to a destination

by following any of the possible moves from a given location2. provide the derived information to smartphones3. develop a prototype that implements this method and test its computational

performance to identify bottlenecks

Summary

Is it possible to combine the alarm clock functionality with the routing functionality - reach a destination by a deadline?

source: http://linuxhub.net/wp-content/uploads/2010/01/alarm-clock.png and http://www.roadmapgps.com/models/tomtom-go-510/scr-navigation-map-6.jpg

Thank you for your time!Q&A