Location Based Notification Systems (LBNS) are those systems which convey informa-tion to the user related to their locainforma-tion using various visual, audio or haptic cues.
Currently mobile phones can provide useful information to the user about places, peo-ple or other objects around them. They have the ability of detecting and reporting ‘nice to know’ situations that are of interest to the user (Li et al., 2008). With the availability of GPS enabled phone, it has become easier to alert the users with information such as
‘close proximity of another friend’ from one’s location, ‘availability of a special deal’ at a nearby restaurant. While the mobile phones provide such services, ideally they can be used without interrupting the current task of the user.
A typical scenario of use of such notification systems is when a local business owner is notified when a valued customer is within some distance of a retail outlet. The customer is delivered a coupon or some notice of a special promotion (Munson and Gupta, 2002).
A more detailed description of the system functionalities of the high level model of a location based notification system is shown in Figure 76. Some of the situations where
notification systems can be used are as follows:
• When tourists enter a tourist area, provide them with historical data and descrip-tions.
• Notify a user when they enter a shopping mall about a sale in a store which is due to finish the next day.
• The user at a fair is notified about the interesting events going on around a particular venue based on the user’s current location.
• The tourist in a new city who is travelling by bus is alerted when approaching the destination bus stop.
While notification can be used to provide such cues to the user, they can also be bene-ficial with regards to notifications regarding public safety and security:
• If there are some road blocks coming up due to heavy traffic or construction, notify the driver beforehand about taking a detour.
• Alert drivers about reducing speed either because they are above the current speed limit on that stretch of road or to warn them against upcoming hazards like low visibility due to fog or wet and slippery road.
• Alert people in a locality with urgent utility information like a power cut or water stoppage.
In Figure 76 we see that the stage 1 for a notification system is that the user ‘subscribes’
(the user chooses to be notified). Stage 2 filters the relevant information for that par-ticular user based on proximity and context in the ‘notification area’ (by calculating user proximity). Stage 3 involves delivering the notification to the user through their preferred methods depending on the ‘client specifications’ (information delivery).
We have seen in the previous chapters how the mobile device can be used for querying spatial information around the user and also how it can help the user get to a par-ticular location. Alert/notification systems are using such devices to notify the user about information that is relevant to the user based on proximity to a person, place or object. There are various kinds of notification systems associated with various kinds
Figure 76: Description of the high level model for location based notification system derived from Munson and Gupta (2002).
of functionalities but in this chapter we try to understand how notifications about a location can be conveyed to the user effectively and in a non-intrusive manner. We will now discuss the various ways of detecting a user location and filtering information to notify users who subscribe to a notification system.
7.2.1 Detection of user location and information filtering
The main functionality of a location based reminder system is that a reminder is deliv-ered for any particular location when the user is within close proximity of that location.
Here the ‘Geo-fence’ concept is used. A Geo-fence can be considered as a virtual perime-ter for a particular area in the real-world. At first the user subscribes to be alerted or notified based on the location and particular task being carried out. There are various ways in which location information can be obtained to notify the user with relevant information. Li et al. used an algorithm that compares locations of cell towers seen by the mobile phone client. This ensures privacy as exact location information is not required or used (Li et al., 2008). Place-its is a location-based reminder application that runs on mobile phones (Sohn et al., 2005). Ludford et al. developed a location-based reminder system, PlaceMail to support everyday tasks (Ludford et al., 2006). Wahid et al. presents Calendar-Based Notifications (CaBN), a notification system designed to deliver personal information in a prioritized fashion (Wahid et al., 2006).
Dhar and Varshney lists the pull versus push based applications as one of the location based service that can be used by advertisers to provide information about deals, offers or sales happening close to the user (Dhar and Varshney, 2011). Here the pull-based services are those where the user initiates the request asking to be served with informa-tion. The push-based services uses the geo-fence concept to deliver information to the mobile terminal (the end user here) with information automatically when events occur such as the user entering a geo-fence of a local business.
Streefkerk et al. describe an intelligent filtering system for police officers for notifications to ensure less interruption or distraction from other incidents (Streefkerk et al., 2008).
Here notifications are filtered based on incident priority, time of day, or other important characteristics such as it being a criminal hotspot (Figure 77). The interface has a notification pop-up on top of the map interface to display notification information.
Figure 77: Screenshots of an LBNS, showing the overview with icons (left), and a notification pop-up (right) (Streefkerk et al., 2008).
7.2.2 Visual representation of notifications/alerts
We see from Figure 76 that the visualisation of the notification cues on the client device using one or more modalities is the last but important phase in a notification system.
System should not be a distraction in dynamic physical environments (Tarasewich et al., 2003).
The Reminder Bracelet (Figure 78) is worn on the wrist and connected to a PDA. It notifies its user of scheduled events in a subtle and silent manner using light, colour and patterns (Hansson and Ljungstrand, 2000). Nair et al. describes SeeVT Alumni Edition which is a location-based tour guide system developed specifically for Alumni visiting Virginia Tech (Nair et al., 2006). They have integrated ‘time as a dimension’
to provide notification cues about historical data about that particular location as they move around campus.
While visual interfaces have the ability to provide notification cues in the most detailed manner, it requires higher attention of the user. Such ‘attention overload’ is not suitable for users especially when the user is on the move in the real physical environment.
Jenkin and Harris added that attention involves the allocation of perceptual or cognitive
Figure 78: Reminder Bracelet worn by a user with 3 LEDs (Hansson and Ljungstrand, 2000).
resources to something at the expense of something else (Jenkin and Harris, 2001). Since humans have a limited amount of resources available for allocation to various tasks, all cannot be attended to at once. Jenkin and Harris also show that although people can attend to one modality (vision, hearing, touch, taste, smell), a colour, a shape, or a location, the decision to attend to one task over the other arises from the importance of the task at hand. Non-visual feedback ensures the attention required from a user is minimal as compared to a visual interaction based system as it is less intrusive. We now look at the ways notification information can be provided to the user via non-visual feedback