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Cartographic Adaptation of Maps for Mobile Devices: A Context Sensitive Approach
Kamal Kant Mishra Assistant Engineer Public Works Department Rajasthan Jaipur-302006 E-Mail: mishra_kamalkant@yahoo.com Milap Punia Scientist, PRSD Indian Institute of Remote Sensing, 4-Kalidas Road, Post Box-135 Deharadun-248001 E-Mail: milap@iirs.gov.in
Abstract
Increasing popularity of mobile devices in past years has drawn attention of map service providers to use these devices for providing geo-information. Mobile devices are supposed to work in highly dynamic environment and demands entirely different output because of inherent mobility. The governing factors present during mobile usage of geo-information cannot be addressed by mere up gradation of hardware. Presence of numerous governing factors present during mobile use of geo-information, by nature which keeps on changing continuously needs to be handled dynamically. These factors include user's profile, preferences, task to be performed, context elements etc. Each set of combination demands entirely different information content and Human-Computer Interaction. Adaptation appeared here as possible solution to address these issues. The objective of this study is to find out the suitability of various adaptive techniques for visualization of geo-information. Rule based approach is also used here. The subjective nature of governing factors demands Human Computer Interaction to be interactive. In the present era of computing where most of the services are being developed for static computing it is needed to pay more attention to make use of geo-information common not only among professionals but among mass population also using popular mobile computing devices. 1. Introduction Demand of maps is growing for decision making and performing various tasks related with spatial information. Their use is changing from supply driven product to demand driven products. Cartographers have exercised their full power to control every bit of map information in the past years and user was able to extract only from these prepared maps. This scenario has changed due to recent developments in digital cartography, now the control has shifted to users who decide which information they want to include (Robinson et al, 1995, pp. 5-6). Development of the Internet and wireless technologies assisted in providing anywhere any time access to updated and latest information. When a person is moving in an unknown area and making a search, only maps can provide desired information in a precise and concise way (Schmidt-Belz et al, 2002). Mobile devices have to perform in the environment where user is always on move; in the state of hurry and different situations are distracting attentions of user away from task in hand (Frank et al, 2004). Presenting map content on screen of mobile device has many limitations but the main constraint of mobile computing is the mobility of user (Noble et al, 1997 and Noble & Satyanarayanan, 1995) and mere up gradation of hardware is unable to solve issues related with mobility (Reichenbacher and Töllner, 2004 & Reichenbacher, 2004). The map supplied to mobile devices needs to be location and context aware in order to achieve objective of user. The cartographic possibilities are that map should be cartographically enhanced and user should be able to perceive what (s)he wanted to refer. Achieving this objective needs knowing user perceptive capabilities. In present scenario adaptation is the only way that can assist in producing personalized maps to mobile device user. These issues strengthen the need of research work to understand contextual elements and processing Geo-information to make it interpretable and available to all. 2. Cartographic Map Adaptation: Concepts and Issues Improving the communication of map information is limited to two approaches, one is to train the map users another is to change the map for users. It is difficult and costly to train large number of users. The choice left is adaptation of map using automatic or interactive methods (Yarnal & Coulson, 1982). The use of word Adaptation representing here changing, modifying map contents to satisfy user, based on context, user task and preferences etc. Holland, 1992 cited in Fairbairn & Erharuyi, 2003 gave a generic definition of adaptation as "Adaptation defines any process where by a structure is progressively modified to give better performance in its environment". Concept of adaptation is further explained by Thévenin & Coutaz, 1999 & Stephanidis et al, 2004 using two complementary system properties: 'adaptability' and 'adaptivity'. Adaptability is capacity of the system to allow user to customize their system to user profile and predefined set of parameters. These parameters can be category of user surrounding condition, user's activity and mobile device's characteristics or so. Adaptivity is the capacity of the system and interaction with mobile computer to perform adaptation automatically during run time. Feeling of absence of user interface and instance of map use taking place in a natural way are the characteristics of an ideal adaptive cartographic system (Meng, 2003). Application of any adaptive method needs adaptable map components. It requires us to understand the adaptable aspect of maps and degree of their adaptability before applying any adaptation method. Different map aspects e.g. legend, title, theme, scale, mapped area, border, symbols, place names etc. take part in producing map output. In addition to the conventional cartographic map elements digital mapping environment also provides some elements which are file format, user interface, function e.g. panning, zooming, hotlinks, selection etc. These map aspects offer higher degree of adaptability compared to conventional map aspects i.e. legend, scale, extent etc. Reichenbacher, 2003 categorized adaptable aspects of map to three main categories. (Refer Table 1)
There are several techniques to perform adaptation and these methods are controlled by several factors. Real application can consist of any one or combination of them. These map adaptation techniques can be classified as follows:
3. Elements of Context & Context Aware Computing Adaptive system needs to be aware about context elements and it is possible only when system identifies the context parameters and then finds their values. A user wants relevant, personalized and context sensitive information and also expects that his mobility do not got affected during information retrieval process. On the basis of these requirements Gökker & Myrhaug, 2002 classified context into environmental, personal, task, social and spatio-temporal context categories (see Figure 1). A context aware system is one which provides relevant services by using context information for a given task (Abowd & Dey, 1999) Context-aware computing describes the situation where a mobile computer is aware of its user's state and surroundings, and modifies its behaviour based on this information. Adaptive system needs to be context aware and it is only possible when the system senses the context elements either actively or passively. In the passive sensing of context user provides information about context elements. This approach has some benefits but human being cannot sense all the element parameters required for making the system context aware. Hence use of sensors that can sense the context element is required  Figure 1: Context in mobile environment and its components (Gokker & Myrhaug, 2002) Context and its elements are the directors of the adaptation process and major factors responsible for Human Computer interaction. Context elements are not easy to interpret and incorporating it in to empirical analysis. Its highly dynamic behavior also adds further complexity. Collecting context information might be easy but it is difficult to manage them. Use of context sensors helps in making system context aware as well as reducing human perception. Sensing context needs sensing Location, Time, nearby objects, Network bandwidth, Orientation, Change in context parameters, other low-level contexts context elements etc (Chen & Kotz, 2000). To make the system context aware following type of sensor can help in sensing the context elements (Schmidt, Beigl & Gellersen, 1998)
 Figure 2: Mobile User Interface The rule-based approach to the adaptation of interface is adopted here (Kraak & Ormeling, 2003, pp-187). The use of If Then else conditional programming (Reichenbacher, 2003) is used for adapting the interface according to the user profile. The knowledge base stored at server side/client side is the main basis of this kind of adaptation. This knowledge base needs to be updated from time to time based on the user survey and their satisfaction level incorporating new technology. It is very complex to decide which adaptive method should take place under a particular set of condition. The most important factors responsible among them are user profile and context information based on that a particular type of adaptation would take place. Adaptation can take place based on a particular type of user or a group of users belonging to same categories. It can be said here that Interface style or type is a function of set of defined factors/parameters. Mathematically it can be represented as I = f (Xi) Where I is interface type, is some function or rule base, Xi is input parameter. It can also be represented as: [Interface (x)] = [Rule Base (x)] [User Profile (x), Device Characteristics (x)] Where for all x ? 0, x belongs to real Number and x ? complex number 5. Evaluation of Adaptive Technique There are many adaptive techniques that can be applied in mobile GIS computing. Most of them are being used on web and controls the process but these techniques have to be evaluated in mobile environment that has different usage requirements and accessed on entirely different hardware. The focus of study concentrates on methods which are governed by context elements. 5.1. Map Orientation Orientation of map plays a major role while user wants to navigate or trying to establish their position with respect to surrounding. Tourist/visitor often found it difficult to identify the landmarks and get orientation while moving in unknown area (Hunolstein & Zipf, 2003. This problem can only be overcome by orientation of map. To orient the maps following approaches can be applied which are keeping North up (conventional approach), keeping target position up, orienting with reference to important land marks (Hunolstein & Zipf, 2003), aligned with reference to long linear object on the map (Zipf, 2002 & Meng, 2004), orienting along with direction of movement and orientation using Least Bounding Box (LBB) (Hermann et al, 2003). In daytime when user is able to recognize the north direction the north direction can be kept up as per standard map convention and user can orient the map mentally (Hermann et al, 2003). In another case the user may needs to orient the map by keeping the target position in up side. Using LBB to orient the map user can opt for keeping target position in up direction (Zipf and Richter, 2002) (See Figure 3). Zipf 2002 and Meng 2004 suggested for orienting the map along the longest linear feature in the map. Uhlirz, 2001 also suggests this approach for orientation of map with respect to largest extension of route, this concept enables user to move along the route much longer without changing or refreshing the display. Orientation along to the direction of movement will prove suitable where user is accessing the map while moving in the same locality, especially when walking in the streets. Another case may arise that user do not recognize the North direction and moving in the streets in this case position of nearby land marks can be used for map orientation (Kraak et al, 2001) User can refer his/her path with reference to the visible nearby landmarks.  Figure 3: Map orientation using LBB
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