The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B5. Beijing 2008 
providers were permitted to use the location capabilities in the 
handset and the network for commercial purposes. This directly 
initiated the development of the wireless location-based services 
(LBS) market. The key players that emerged in the wireless 
device manufacturing industry are SnapTrack (acquired by 
Qualcomm in 2000; 
http://www.qualcomm.com/about/qct_redirect.html) and SiRF 
(http://www.sirf.com/). The important development for the new 
markets for LBS solutions was the emergence of GPS-based 
PND business by companies such as Garmin, Navman, Trimble, 
Magellan, and TomTom. The current trend is that increasingly 
more devices, such as, for example, the Blackberries, become 
connected wirelessly and provide some navigation information. 
Also, the iPhone launched by Apple supports Google maps on 
the device, and it is expected that the next generation iPhone 
will offer a significant improvement in geographic navigation 
(GPS) and management tools 
(http://lbs.gpsworld.com/gpslbs/article/articleDetail.jsp?id=466 
339&sk=&date=&pageID=2). It is also important to mention 
here that high quality and up-to-date digital maps are crucial to 
reliable personal navigation. This part of the consumer market is 
well covered by Navteq (http://www.navteq.com/) and Tele 
Atlas (http://www.teleatlas.com/index.htm) who deliver digital 
maps and dynamic content that power the world’s demand for 
navigation and location-based applications. 
The improvements in GPS receiver size, performance, and cost 
over the past few years have stimulated an upsurge of consumer 
GPS products, which followed an increased public awareness of 
the potential utility of GPS. The GPS-based consumer products, 
such as car navigation systems, GPS-enabled PDAs and 
locatable mobile phones, have flooded the marketplace. Yet, 
general misunderstanding of the GPS limitations often leads to 
consumer dissatisfaction due to the low position accuracy their 
devices may furnish, or a lack of any positioning information 
under some circumstances. Consumers expect a navigation 
product simply to work, regardless of the conditions and the 
surrounding environment. 
Although high-sensitivity receivers, or assisted-GPS (A-GPS), 
enable operation with much weaker signals (even indoors), 
there are still situations where even A-GPS does not provide 
sufficiently accurate position fix within an acceptable time 
interval. Consequently, users in high multipath or extremely 
weak signal environments may experience low positioning 
accuracy and/or long delays in achieving a position fix. Even if 
some contingency § strategies, taking effect when A-GPS fails, 
are implemented to provide the user with a gracefully degrading 
position fix service, the position fix will eventually become 
unavailable. As much as the consumer market would like to 
avoid such situations, they are inevitable, unless some 
augmentation is used with GPS or even A-GPS. This 
increasingly leads to multisensor solutions that are not yet very 
§ According to 
http://lbs.gpsworld.com/gpslbs/content/printContentPopup.isp7i 
d=262078 “The simplest fall-back method is Cell ID, by which 
a user’s position is assumed to coincide with the location of the 
cell tower handling the user’s call, or the centroid of the 
coverage area of that particular cell. In either case, the assumed 
user’s position could be wildly inaccurate, depending on the 
network’s tower spacing. Researchers in the United Kingdom 
have invented a fail-back technique that uses network signal 
timings to provide a user’s phone (terminal) with a synthetic 
clock, synchronized to GPS Time. With such an accurate clock, 
the terminal can be positioned using a similar technique to that 
used by GPS but by using the network signals themselves.” 
common within the consumer market, but substantial research 
and conceptual work has been conducted in recent years to 
develop reliable and ubiquitous personal navigation device for 
pedestrians (e.g., Retscher 2004a and b; Retscher and Thienelt, 
2004; Kourogi et al., 2006; Lachapelle et al., 2006) as well as 
military and emergency personnel (Grejner-Brzezinska et al., 
2006a and b, and 2007a and b; Moafipoor et al., 2007), who 
operate in environments where GPS may not be always 
available, while their navigation fix is crucial for the combat or 
emergency mission. 
Pedestrian and personal navigation** systems require continuous 
positioning and tracking of a mobile user with a certain 
positioning accuracy and reliability. However, navigating in 
urban and other GPS-impeded environments, such as mixed 
indoor and outdoor areas, is a very challenging task. These 
systems require multiple navigation technologies to be 
integrated together to form a multisensor system, as mentioned 
above, in order to serve as many different environments as 
possible for seamless and reliable navigation. Example 
technologies suitable for multisensor solutions supporting 
personal navigation include GNSS (Global Navigation Satellite 
System), ground-based RF systems, such as pseudolites (e.g., 
Barnes et al., 2003a and b) suitable for confined and indoor 
environs, as well as cellular phone positioning for absolute 
position determination, dead reckoning sensors (e.g., magnetic 
compass, gyroscopes, accelerometers and barometers) to 
determine orientation, distance traveled and height. For location 
determination of a pedestrian in multi-storey buildings the 
Wireless Local Area Networks (WLAN) (e.g., Wang et al., 
2003; Li et al., 2006), or transponders or beacons installed in 
the buildings (e.g., Pahlavan et al., 2002) are increasingly used. 
Other indoor positioning systems include so-called Active 
Badge Systems (e.g., Hightower and Boriello, 2001). These 
methods can provide few-meter accuracy for indoor tracking 
and positioning. Robustness of the ultra wideband (UWB) 
signal to multipath fading and its high penetration capability 
makes it another technique suitable for indoor positioning. The 
indoor UWB-based navigation systems (fundamentally 
designed for wireless communication, navigation being usually 
a tag-along application), which work in the bandwidths in 
excess of 1 GHz, measure accurate time of arrival (ToA), the 
difference of ToA of the received signals for the estimation of 
distance to mobile user (e.g., Pahlavan et al., 2002; Win and 
Scholtz, 2002; Ni et al., 2007). The UWB ranging and 
communication scheme may employ one or more of the 
following techniques: time division multiple access (TDMA), 
frequency division multiple access (FDMA) or code division 
multiple access (CDMA). A direct sequence (DS)-CDMA 
scheme is a preferred UWB scheme for providing ranging 
resolution and identification of base stations (see, e.g., 
http://www.wipo. int/pctdb/en/wo.jsp?IA=US2005004936&DIS 
PLAY=DESC for more details). Another method considered in 
indoor navigation is based on optical tracking systems also 
referred to as image-based systems. This method has been 
researched by, for example, Veth and Raquet (2006a and b) in 
connection with inertial technology. In general, the image-based 
tracking systems could provide high positioning accuracy and 
resolution, but these are a function of the type of sensors used 
(primarily its angular resolution), distance between the target 
and the sensor, specific application and the environment 
(outdoor vs. indoor). 
Personal navigation is understood here as navigation of 
military and emergency personnel, while pedestrian navigation 
refers to all other uses for location/navigation of a mobile user.