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. [email protected], [email protected]
AND
MIKE KNIGHT [email protected]
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 associated 588 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 enough LOCATION 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 in 590 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 Code 594 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 barcode LOCATION 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 phone 596 G. SAEED, A. BROWN, M. KNIGHT
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