Leif Oppermann

For Mobile GamesMobile Gaming Workshop, Lübeck, 29.09.2009

Overview of this talk

Key task: Model location Decide on trigger

Constrained by technology Be flexible in your model

Part 1: why? Part 2: how?

No single tech fits all needs

Understand the infrastructure Understand location in the design

What are your precision requirements?

Findings from seminal work

Cyberguide (1995), GUIDE (1997), Mercury (2008) a) positioning technology does not have

to be overly precise in order to effectively support a location-based experience

b) the context of the current location is often more important than absolute position coordinates

c) people escape the context when using a location-based system

Relation to mobile games

ARQuake High accuracy

Mogi Mixed accuracy

Love City Enough locations

Be flexible with location!

Love City prototype was cell ID Love City final was operator based Both versions used the same content This was made possible through

location abstraction

Location mechanism

Focus on experience first, tech later Decouple thinking from technology

While staying feasible to ensure completion

Hence, use a flexible and extensible abstract location model (this work)

Works with GPS, Wi-Fi, GSM, etc. This is not sensor fusion

They fuse on absolute position I fuse on abstract location

Position vs. location

Let’s keep the terms separate Position

Point in coordinate system (abs. or rel.) e.g. 52.953412, -1187508 in WGS84 (GPS)

Location Disembodied concept “home”, “office”, “bus stop”, “stadium” Humane, but potentially ambiguous Opportunity for interaction

Space vs. place (1)

Harrison and Dourish (CSCW 1996) “people are located in space,

but act in place” A place is a space with something added

○ House vs. home

Related work

Ashbrook & Starner “Learning significant locations and …”, ISWC, 2002

Hightower, PhD thesis 2004 “want to reason about place instead of, or in

addition to coordinates”

“Learning and recognizing the places we go” paper, Place Lab, Ubicomp 2005

Nurmi & Koolwaaij “Identifying meaningful locations”, 2006

Space vs. place (2)

Sociological, human factors perspective: “Space is the opportunity, place is the

understood reality”

Place can only be designed for Humans have to accept the space to

transform it into a place

To facilitate this transition: Support human appropriation of space Be flexible about structure of space

Abstract Location Model

Technological perspective Space is diverse in pervasive computing

GPS, network space, etc.

Hence, subdivide space further Metric level: position

○ GPS, Wi-Fi, GSM, etc. Abstract level: location

○ “House”, empty shell○ Associate with meaning○ Bridge

Metric Level Abstract Level Interactional Level

Term Position

(Space)

Location

(Space)

Place

Example GPS coordinates,

GSM cell ID, Wi-Fi

fingerprint

“House”

An empty shell; needs

to be filled with

meaning, i.e. content

and regions in our

case.

“Home”

A location with

associated

semantics; content

and regions in our

case.

Usage Define regions in

space according to a

particular metric

Links the metric level

with the interactional

level

Point of interaction

with end user

Abstracts user experience from technology

Advantages of this model

Abstract location is an empty hook Opportunity to associate meaning to it Without tying it to any spatial representation Digital content, region definitions, meta data

Abstracts user experience from technology

This facilitates appropriation During design phase But also later, when deployed

Reproducible ID strings

Sensor data needs to be referenced by unique ID-strings Database storage Unambiguous mapping

Runtime performance on mobile device Location: Unique name + human

readable name Region (definitions of space): ditto

Data flows from sensors upwards Intersect sensor data with location data Trigger location events Send all to Location Aggregator

Which is the API

Upshot

Model does not try to be clever Forward all location events,

let application decide Lesson from Mercury: use hierarchy!

Model is flexible GPS, Wi-Fi, GSM supported, more possible

Model has been used Love City and Rider Spoke retro-fit Sillitoe Trail uses reference

implementation

Thanks for your attention

Questions, please

LXO@cs.nott.ac.uk http://www.mrl.nott.ac.uk/~lxo/

Model is available http://sourceforge.net/projects/pytheas/