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Cartographic Adaptation of Maps for Mobile Devices: A Context Sensitive Approach
5.2. Focusing User Attention and Content Generalization
Focusing on feature of interest can help in transferring desired information and interpretation of map. Focus area can be Area - country, province, city etc., Map layer, Map feature etc. Small screen of mobile computers have requirement of displaying simple map for easy interpretation by user. State of always being in hurry also limits interpreting power of user. The information display on mobile display needs special adaptation to counteract the small screen size and time constraints of user (Baus et al, 2001) The maps need to highlight the required information in order to ease the Geoinformation communication (Zipf & Richter, 2002). Use of following methods can focus the user's attention on desired information:
Scale of map is very important aspect of map and most frequently used operation in digital mapping. The mobile device users always have lack of time and therefore the map content should be delivered at optimal scale. Two option are possible one is providing map at the scale such that the all desired content seen at once. Second option is map delivered at scale predefined by user (Brown et al, 2001). Visualization of map at optimalscale can be achieved by using Least Bounding Box (LBB) for optimal scale (Zipf & Richter, 2002), use of lens or texture filter (Kraak & Ormeling, 2003) and using variable scale maps (Harrie et al, 2002). On the basis of map content zooming can be performed by three different ways static linear zooming, static stepped zooming and dynamic zooming (Brown et al, 2001). The later one will prove better in mobile environment because the content will remain readable at smaller scale while static stepped and linear zooming will result into non-readable data at smaller scale. The concept of Least Bounding Box can provide map at optimal scale for default retrieval. If Axis of route be displayed oriented along diagonal of the screen then display scale will be maximum compared to any other orientation (See Figure 3), for further zooming in/out use of lens tool or texture filter as suggested by Kraak & Ormeling, 2003 can be used. This approach to orient the map is much better because both start point and destination point can be seen at a glance and for this diagonal of screen is most suitable to get optimal scale to save time. Another approach to visualize maps without changing scale of whole map to see a portion of map at larger scale is the use of magnifying lens/texture filter (Reichenbacher, 2001). This tool provides closer view of the feature without changing the map scale and thus provides overall view of map (Kraak & Ormeling, 2003, pp 270). The zooming using click event suitable with novice user while zooming with track rectangle command may prove much better with the users who are familiar with computing. The slider control can provide the smooth transition between two scales. Using variable scale map devised by Harrie et al, 2002 for visualizing geo-information in personal navigation system is able to provide an overview map in the vicinity of user. This approach displays area in the vicinity of the user at bigger scale than the area that is farther. This method of map representation can provide better output and panning and zooming can be avoided up to some extent. (See Figure 4)  Figure 4: Variable scale map area in the circle near to user's position is shown at larger scale and rest of the data is shown at small scale (Source: Harrie et al, 2002) 5.4. Colour Scheme and Cascading Style Sheets Colour scheme of map helps in better visualization and interpretation of map. The factors responsible for colour scheme are user preference, experience of map use etc. The age and gender of the user also plays role in likeness of colour scheme but this issues will further leads to special research. Individual user's preferences are also requires different colour scheme. User's physical characteristics i.e. colour blindness; impaired visibility also requires use of special colour scheme. The background colour or image file enhances map experiences of user and help in drawing attention of user on feature of their interest. Visualization style change the map output in drastic way. Every user likes different of styles. Use of CSS (Cascading Style Sheets) can help here and can thus help in better user experience. CSS is a method of creating one file that stores the entire theme of user like background colour, font type, size, style, spacing etc. to web documents (URL 1 & URL 3). This file stores all statement/rule that governs the rendering properties of the web document (URL 2). Use of CSS while presenting maps on mobile device can help the user, to choose the appropriate colour scheme or any other aspect of maps with relation to their chosen map aspect. 5.5. Map Symbology for Mobile Devices These are the Symbols that play very important role in phrasing map document. Symbols may or may not be self-explanatory and legend may be required to interpret the information hidden behind the symbols. There are various elements that affects the symbolization style i.e. user task, perception capability, cognition power, physical characteristics etc. Pictorial symbols are self explanatory while geometrical and letter/number symbols require legends to convey the meaning. Hence in the case of using these symbols over mobile devices pictorial symbols are more suitable as later requires legends to explain and switching legend on/off will require extra input from user. Visually impaired persons require large symbols and less detail. Children like picturesque symbols and don't like abstract symbols and information (Zipf, 2002). Changing the symbology for whole map can be done with exchange in style sheet or XSLT (Reichenbacher & Tollner, 2004). Symbolization of map has big potential to explore from the adaptation aspect of visualization. 5.6. User's Position in Map Position of user on map plays an important role in performing task in mobile environment and help greatly in getting orientation. For a user moving in unknown area it is very difficult to get orientation if his/her position is not shown on the map (Baus et al, 2001). In these conditions user can get orientation with reference to features in front of them. The position of user is mainly governed by task. If position of user is not chosen accordingly map scale will got affected severely. It is recommended to place user's position for navigational task on bottom portion of screen. For other task like searching for something user's position on the screen should be decided as per the map retrieval and orientation of map, but identifying and locating (own and others) task will be more effective if user's position will be shown in the centre of the screen. 6. Conclusion This research work has discussed about adaptation and various adaptive techniques for mobile devices. Maps displayed on Mobile devices needs to provide access of geo-information to the diverse group of users for decision making and performing various user tasks during mobility. The information content delivery on mobile devices needs to be context sensitive and the interactive system needs to intelligent enough to understand user behaviour and adapt the system accordingly. The adaptable aspects of the map require identification of adaptable aspects of map and their degree of adaptability. The adaptable aspects of map will vary depending on the objective and type of information requirement. Adaptation of maps is required mainly because of two reasons one is technical limitations of mobile devices and another is usage of geo-information during mobility. The technical advancement will overcome the limitations of mobile devices in near future but the usage issues can only be solved by theoretical approaches. Mobile computing requires dynamic computing behaviour, which changes with change in context elements. It can be achieved by making system context aware. Some parameters like location, time, QoS etc. can be sensed by special sensors but parameters like personal profile, mental state of user etc can only be accessed by interactive GUI. Rule based approaches for developing of adaptive GUI can be used effectively and has enough scope to meet changing context requirements. The mixed approach of automatic approach for objective and interactive approach for subjective nature of parameters is applied to design the GUI. Most of the parameters responsible for adaptation of map visualization are quite subjective and behaves differently in different situation. It requires adaptive system to respond dynamically during run time. 7. References
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