LOCATION AWARENESS IN A MOBILE DIGITAL ARCHITECTURAL GUIDE
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LOCATION AWARENESS IN A MOBILE DIGITAL
ARCHITECTURAL GUIDE
GHOUSIA SAEED, ANDRÉ BROWN
Department of Architecture, N-W.F.P. University of Engineering and
Technology, Abbottabad Campus, Abbottabad, Pakistan and The
University of Liverpool, School of Architecture, Liverpool L69 7ZN, UK.
ghousia@nwfpuet.edu.pk, andygpb@liv.ac.uk
AND
MIKE KNIGHT
m.w.knight@liv.ac.uk
Abstract. One of the core issues relating to the delivery of architectural
information to mobile digital devices is the real-time location awareness.
This paper describes the research on different computing and wireless
techniques and technological systems for real-time navigation support
and location based information delivery on a digital handheld device for
a pedestrian user on the move. This work investigates the applications of
GPS, WiFi, 2D barcode and NFC systems in a mobile city Architectural
guide.
Keywords. City guide, real-time location awareness, GPS, 2D barcode,
NFC.
1. Background
A number of research projects have shown that a city guide - digital city model
with connected database of information - can be exploited for a number of
purposes like visualisation, development, planning, commerce, transport, tourist
information and for discovering the city for a wide variety of users, both
professional and non-professional (Depuydt et al., 2006; Vainio and Kotala,
2002; Rakkolainen and Vainio, 2001; Berridge et al., 2002; Umlauft et al.,
2003; Koutamanis, 2007). Research in the field indicates that real-time location
and routing information improves the utility of a mobile digital city guides and
can contribute to effective delivery of digital city models and associated588 G. SAEED, A. BROWN, M. KNIGHT
information to digital mobile devices. So, there has been experimentation and
development of mobile city guides that provide location based information
and routing functionality such as
Cyberguide (Long et al., 1996), HIPS (Broadbent and Marti, 1997),
OnTheMove (Kreller et al., 1998), GUIDE (Cheverst et al., 2000), Deep Map
(Rakkolainen and Vainio, 2001), 3D City Info (Vainio and Kotala, 2002), LoL@
(Umlauft et al., 2003) and DTG (Kramer et al., 2007).
Long et al. (1996) have undertaken the Cyberguide project that involves
the building of prototypes of a mobile context-aware tour guide that provide
information to a tourist, based on knowledge of position and orientation. The
project considered several methods for sensing user location. The outdoor
version used GPS. Kramer et al. (2007) in the DTG system utilise two modes
to facilitate tour for the city of Görlitz. The first mode aims to provide
personalized tours, whilst the second mode computes no tour plan but aims to
provide the context based information whenever requested by user. This system
uses GPS technology for navigation. However, the authors mention that in
some cases tourists got lost, probably because of misleading direction
information given by the mobile navigator due to bad GPS accuracy. ‘LoL@’
is a location-based multimedia UMTS application that aims at supporting
tourists for city navigation. In response to the inaccuracy of GPS receiver
information in narrow street canyons, this project uses a hybrid routing concept,
combining automatic user positioning with GPS and some user interaction.
The work reported in this paper is a part of an on going research project,
‘City in the Palm of your Hand’, that works under the umbrella of the CAAD
research unit (CAADRU) at the University of Liverpool, UK. The main aim of
this project is to deliver city architectural information wirelessly to digital
handheld devices on location using digital city model and city architectural
database. The project deals with a range of issues relating to the delivery of
achitectural information that includes textual, audio, video, 2D and 3D graphic
information to mobile digital devices on site. These issues are being investigated,
developed and refined as part of this project that is being applied in the city of
Liverpool. The outcomes have broader implications for other applications of
the theories and technologies related to pedestrian guides.
Clearly, a core issue relating to this and any other mobile city guide is the
real-time location awareness of user and then delivery of location based
architectural information on the fly. Navigation support in city guides let user
to obtain routing information on handheld device to take the helm through
physical environment and to locate her and points of interest in the surrounding
areas. Location based information delivery allows a user to obtain information
on the surrounding attractions. This needs a relationship between navigation
and communication systems. It involves making the city guide smart enoughLOCATION AWARENESS IN A MOBILE DIGITAL... 589
to know its own location as well as the location of nearby objects, before
delivering any additional information to the user on site. We investigate the
applications of Global Positioning System (GPS), WiFi, two dimensional (2D)
barcode and Near-Field Communications (NFC) systems in a mobile
architectural guide for the issues of location placement of the user, and delivery
of location based information to the user on the move.
2. Global Positioning System (GPS)
Digital navigation systems are generally reliant on satellite navigation
technology such as GPS for location and routing information. The GPS is the
first and the only fully functional satellite navigation system as of 2008. GPS,
initiated in 1973, is currently the most widely known location-sensing system
for automobile navigation. However, the work described in this paper
investigates and explores the accuracy and reliability of this technology for a
pedestrian user interacting with a digital city model and associated city
architecture information database on a digital handheld device while walking
around the city.
As part of this work, a number of experiments were conducted in carefully
selected areas of the city of Liverpool to get an idea of a conventional GPS
receiver’s accuracy. Results show many problems with using GPS in the urban
environment for this purpose, due to the variable nature of GPS’s accuracy and
availability. Both typical and gross errors were found in the GPS receiver data.
EXPERIMENTS
These experiments were concerned with the graphical visualization and analysis
of GPS receiver data. The information from these experiments was used to
establish a range of errors that GPS-enabled handheld device like PDAs
experience in urban locations. The work examined and analysed a GPS
receiver’s data for use in the ‘City in the Palm of your Hand’ city guide. Eleven
experiments were conducted in different locations, open and obscured, and in
different receiver’s conditions, stationary and moving. Results of experimental
data suggest that a basic GPS receiver data is neither reliable nor accurate
enough for position and routing information to be of use in the city guide.
It is clear from figure 1 that a few metres deviation from an actual route can
change the views totally. Actual route followed was the left footpath (figure 1)
in experiments 1 and 5. While GPS receiver calculated the position to be the
right footpath in experiment 1 and inside the Abercromby Square was calculated
in experiment 5. Let’s imagine a user walking over the left footpath and seeing
outside of buildings at right and Abercromby Square at her left, as shown in590 G. SAEED, A. BROWN, M. KNIGHT
figure 1. However, the digital representation connected with GPS receiver will
show inside of the Abercromby Square to the user on screen of handheld device
at one time, the wrong footpath at second time and some other view next time
– resulting in confusion.
Figure 1: A few metres deviation from actual route can totally change the view, Upper.
Actual position of GPS receiver and two locations indicated by the receiver, Lower. The
actual view suggested by the receiver is very different to the actual shown in Upper
Experiment 10 was conducted by placing GPS receiver at fixed point in an
open location, while GPS receiver was placed at fixed place in an obscured
location for 30 minutes of the experiment 7. Imported track logs in these two
figures show as data is of moving receiver, but actually the GPS receiver
remained at a fixed position during both the experiments (figures 2 and 3).
Figure 2. Snap shot showing data points in ArcMap of Experiment 10
[open location – receiver static]LOCATION AWARENESS IN A MOBILE DIGITAL... 591
Figure 3. Snap shot from ArcMap showing data points of experiment 7
[obscured location – receiver static]
It was found that the errors and error intensities are different at different
times for the same area. Similarly, errors and error intensities are different for
different areas. The GPS receiver often fails to deliver continuous positioning
information in urban canyons and obscured locations. The more obscured the
location, the greater the ‘down time’ where no readings are available. The
GPS receiver takes a few seconds to a few minutes to acquire position data,
when it is switched on for the first time and also when it starts again after
interruption due to tall buildings, dense foliage or any other obstruction close
to GPS antenna.
Unreliability and inaccuracy of GPS positioning and routing information
suggested the investigation of other wireless and computing technologies to
provide more precise, acceptable and reliable dynamic interaction on location
with a digital urban model and an associated city information database on site.
In this research case, use of RFID/NFC and 2D barcode systems was examined
and the potential for the use of WiFi and mobile cells is noted.
3. NFC System
Automatic contactless identification systems have emerged as one of the
dominant technology trends of last few decades. Contactless systems use Radio
Frequency (RF) for transfer of power and data, hence are called Radio Frequency
IDentification (RFID) systems. Applications of RFID technology are becoming
widely used for toll collection, contactless ticketing, credit cards, smart cards,
antitheft alarm system in shops, remote keyless entry system for cars, control
access inside buildings, animal tracking and e-passports.592 G. SAEED, A. BROWN, M. KNIGHT
The technology that NFC is based on, RFID, is nothing new
(www.rfidjournal.com/article: Jan 2008; Landt, 2005). However, a new set of
applications and services are opening up as NFC integrated into mobile phones,
given their ubiquity and ability to have more features crammed inside them
(www.technologyreview.com: May 2007). NFC combines two established
technologies; RFID tags and wireless readers. An NFC system, using RFID
tag and NFC-enabled mobile phone reader is shown in figure 4.
NFC is a short-range, standards-based wireless connectivity technology that
uses magnetic field induction to enable communication between electronic
devices in close proximity. The interfaces operate in the unregulated RF band
of 13.56 MHz. Generally speaking, NFC operating distances is 0~20 centimetres
in air. Currently it offers data transfer rates of 106 kbit/s, 212 kbit/s and 424
kbit/s, and higher rates are expected in the future.
The NFC can operate in either of two modes; active and passive. In active
mode, both devices generate their own radio field to carry and transmit the
data. In passive mode, only one device generates a radio field. The passive
mode of communication is very important for battery-powered devices like
mobile phones and PDAs that need to prioritize energy use.
According to the ABI research, half of all mobile handsets will support
NFC by 2010 (www.innovision-group.com: May 2007). The NFC-enabled
devices have been used in numerous NFC projects around the world like ‘O2
Wallet scheme’ (www.rfidjournal.com: June 2008), ‘Touch & Travel’
(www.nxp.com: June 2008), and many more (www.nokia.com: Jan 2008).
Figure 4. NFC reader built into a mobile phone reading an RFID tag
NFC SYSTEM – APPLICATIONS
NFC systems are being used for payment and financial applications. NFC
systems are also being used to access by permitting simple, wireless connection
facilities to a remote server, from which data can be downloaded. It is this
facility that the ‘‘City in the Palm of your Hand’’ project is seeking to exploit.
NFC devices’ mode of operation can be categorised as illustrated by figure 5.LOCATION AWARENESS IN A MOBILE DIGITAL... 593
Figure 5. Uses of NFC system
In service initiation mode, the NFC device is capable of reading an NFC
tag. In this set up, user touches or wave over an NFC-enabled device, such as
PDA or mobile phone, against a specially located RFID tag, this then typically
provides a small amount of information to the device. This can be few textural
lines, a web address (URL), phone number or a specific ID that connects
handheld device with backend database.
RFID tags can be placed almost anywhere; the particular focus of this work
is in locating them on the selected buildings in Liverpool World Heritage area
and on the University campus sites. The tags’ stored information then can be
accessed by touching them with NFC-enabled digital handheld devices.
4. 2D Barcode System
1D barcodes have been criticised often for having a low density of coded
information, as 1D barcode symbol seldom represents more than a dozen
characters and acts an index to a record in a database. The need for a barcode
to be a portable database rather than just a database key leads to the development
of 2D barcode.
At the end of 1980s, 2D barcodes appeared (Gao et al., 2007). These were
first introduced by US firm Intermec corporation in 1987 when they announced
Code 49, designed by D. Allais (Pavlidis et al., 1992). Visually 2D barcodes
look like lots of small squares/rectangles, generally black and white, in an area
similar to the size of a postage stamp. 2D barcodes are symbols made of pattern.
These patterns are usually made up of tiny square graphics, and can handle
upto 7000 characters depending on the standard used. Figure 6 shows different
kinds of 2D barcode symbol.
Figure 6. 2D barcode symbols Left. MaxiCode Right. QR Code594 G. SAEED, A. BROWN, M. KNIGHT
Barcode symbologies, like languages, are given different names, like
PDF417, DataMatrix, QR code, VS code, Colorcode, Visual code and Shotcode.
Different symbologies are developed to satisfy various application requirements
(www.dataintro.com: Nov 2007) .
2D BARCODES WITH CAMERA PHONE TECHNOLOGY
Mobile phones and barcode technologies have been combined to the advantage
of user. A camera phone, programmed to interpret barcode images, generates
the barcode value which is used to identify the object. By connecting online,
user can then get access to a wealth of information about the object. Users
photograph barcode and their camera phones decode information embedded in
the codes and display, manipulate, and store the information on their mobile
devices, as illustrated in figure 7.
Figure 7. Decoding 2D barcode with camera phone
5. NFC/2D Barcode Systems to Deliver City Architectural Information
System on Location
The ‘City in the Palm of your Hand’ project aims to combine user’s real world
contextual information (location and routing) with associated city architectural
information on a digital handheld device, and technological glue is needed to
combine real and virtual worlds’ information on the fly. Therefore, the main
purpose of an RFID tag/2D barcode is to act as technological/digital glue to
join physical objects wirelessly with a city information database, thousands of
miles away.
The work aims to provide pedestrian user with real-time location awareness
and then facilitating navigation to target. RFID tags and 2D barcodes can be
used as a key to access a database of location and routing information, as created
by the ‘City in the Palm of your Hand’ project, on location. Both 2D barcodeLOCATION AWARENESS IN A MOBILE DIGITAL... 595
and RFID systems are capable of storing a link/information to a backend
database of information. A user can download the relative information on her
handheld device by accessing this link. RFID tags, with specific information
related with the buildings and their surroundings or with ID for backend database
can be affixed on buildings and a pedestrian user, while doing a physical tour,
can get the stored information on screen of the NFC enabled handheld device
just by touching or waving the mobile device over these tags (figure 8). Similarly
2D barcodes with required stored information can be glued on buildings or
landmarks to be identified in the city. The 2D barcode system allows its users
to point camera phone at the barcode fixed to the buildings or other objects in
order to retrieve stored information that is then delivered to the screen of their
phones (figure 9).
Figure 8. Receiving stored RFID tag information on the screen of
NFC-enabled mobile phone
Figure 9. 2D barcodes with stored information can be affixed on buildings and user can
retrieve stored information on the screen of camera phone596 G. SAEED, A. BROWN, M. KNIGHT
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