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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)
Table 1: Adaptable map components (Adapted from Reichenbacher, 2003)
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, ƒ 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
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
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)
| Geo-information | User interface | Visualization |
| Encoding-Format | Functions | Map Section |
| Amount of data-Content | Interaction mode and style | Map Scale |
| Classification | Methods-static/dynamic | |
| Grouping | Dimensions | |
| Level of details | Graphical elements | |
| Geographical area | (Symbols & text styles) |
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:
- Adaptation of Geo-information:
- Changing Level of details and generalization degree (Robinson, 1995 & Reichenbacher, 2004)
- Changing Map file format (Reichenbacher, 2004)
- Classification (Reichenbacher, 2004)
- Information filtration (Reichenbacher, 2004)
- Adaptation of user interface
- Adapting User Interface by restricting access level or simplifying the interface etc. (Reichenbacher, 2004)
- Web like functionalities using different type of zooming, panning, rotating, selection, hotlinks etc. (Brown et al, 2001 & Frank et al, 2004)
- Adaptation of visualization of map content:
- Orientation of Map (Hunolstein & Zipf, 2003, Hermann et al, 2003, Zipf, 2002 & Meng, 2004)
- Change in Map scale (Reichenbacher, 2004)
- Changing Colour scheme (Zipf, 2002)
- Changing Symbolization Style (Reichenbacher, 2004)
- Changing position of user on map
- Focus on area of interest (Zipf, 2002, Zipf & Richter, 2002 & Brown et al, 2001)
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)
- Optical/Vision: Detection of landmarks, objects, people etc.
- Audio: Basic identity of speaker etc.
- Motion: Speed, acceleration and inclination
- Location: GPS can sense accurate location.
- Bio-Sensors: Emotional state of the user.
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, ƒ 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
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:
- Changing contrast and colour used: Bright and shiny colours are more noticeable than grey colour (Zipf & Richter, 2002). The colour of feature that needs to be focused can be of higher contrast while other features can be subdued (Meng, 2004).
- Dynamic methods: Using dynamic visualization, animation i.e. blinking the feature, animation effect etc. required feature can be focused.
- Changing the size of feature like increasing the width of road, size of building feature to draw attention etc.
- Map generalization: Generalizing the map feature other than required layer can also be used for drawing the attention. (Zipf & Richter, 2002).
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
- ABOWD, G. D. and A. K. DEY (1999): Towards a Better Understanding of Context and Context-Awareness, In Proceedings of the 1st International Symposium on Handheld and Ubiquitous Computing, 1999, Karlsruhe, Germany, pp. 304 - 307.
- BAUS, J., A. BUTZ, A. KRUGER and M. LOHSE (2001): Some Remarks in Automated Sketch Generation for Mobile Route Descriptions, Presented at 1st International Symposium on Smart Graphics, March 21st -23rd, 2001, Hawthorne, NY.
- BROWN, A., N. EMMER and J. V. D. WORN (2001): Cartographic Design and Production in the Internet Era: The Example of Tourist Web Maps, The Cartographic Journal, Vol. 38, No.1, pp. 61-72.
- FAIRBAIRN, D. and N. ERHARUYI (2003): Adaptive Technique for Delivery of Spatial Data Technique for Mobile Devices, In: GARTNER, G. (Ed.) 2nd Symposium on Location Based Services and Telecartography, ICA Commission on Maps and the Internet, January 28th - 29th, 2004, Vienna, Austria.
- FRANK, C., D. CADUFF and M. WUERSCH (2004): From GIS to LBS: An Intelligent Mobile GIS Presented at GI-Days 2004 in collaboration with Intelligent Spatial Technologies, July 1st -2nd, 2004, Muenster, Germany.
- HARRIE, L., L. T. SARJAKOSKI and L. LEHTO (2002): A Variable-Scale Map for Small-Display Cartography, Proceedings ISPRS Symposium on Geospatial Theory, Processing and Applications, Ottawa, Canada.
- KRAAK, M. J. and F. ORMELING (2003): Cartography: Visualization of Spatial Data, Second Edition, Harlow (England), Pearson Education Ltd.
- MENG, L. (2003): About the Emotional Requirements of Map Users, Internationales Korrespondenz-Seminar. In: Diskussionsbeiträge zur Kartosemiotik und zur Theorie der Kartographie. Wolodtschenko & Schlichtmann 2003 (Hrsg.), TU Dresden, pp. 27-34.
- MENG, L. (2004): About Egocentric Geovisualization, Proc. 12th International Conference on Geoinformatics - Geospatial Information Research: Bridging the Pacific and Atlantic, June 7th -9th, 2004, University of Gävle, Sweden.
- NOBLE, B.D. & M. SATYANARAYANAN (1995): A Research Status Report on Adaptation for Mobile Data Access, SIGMOD Record, 24(4), Dec. 1995, pp.10-15.
- NOBLE, B. D., M. SATYANARAYANAN, D. NARAYANAN, J. E. TILTON, J. FLINN & K. R. WALKER (1997): Agile Application-Aware Adaptation for Mobility, Proceedings of 16th ACM Symposium on Operating Systems Principles, October 1997, Saint-Malo, France, pp.276-287.
- REICHENBACHER, T. (2001): Adaptive Concepts for a Mobile Cartography, Supplement Journal of Geographical Sciences, Vol.11, pp. 43-53.
- REICHENBACHER, T. (2003): Adaptive Methods for Mobile Cartography, Proceedings of the 21st International Cartographic Conference (ICC), August 10th -16th 2003, Durban, South Africa, pp. 1311-1322.
- REICHENBACHER, T. (2004): Mobile Cartography- Adaptive Visualisation of Geographic Information on Mobile Devices, Doctoral Thesis, Institute for Photogrametry and Cartography, Technical University of Munich.
- REICHENBACHER, T. and D. TÖLLNER (2004): Implementation of an Adaptive Mobile Geo-visualisation Web Service, In: GARTNER, G. (Ed.) 2nd Symposium on Location Based Services and Telecartography, ICA Commission on Maps and the Internet, January 28th - 29th, 2004, Vienna, Austria. pp. 17-23.
- ROBINSON, A. H., R. SALE, J. L. MORRISON and P. MUERCKE (1995): Elements of Cartography, 6th Edition, New York etc., John Willey & Sons Inc.
- SCHMIDT, A., M. BEIGL, and A. W. GELLERSEN (1999): There is More to Context than Location, Computers & Graphics, Vol. 23, No. 6, pp. 893-902.
- SCHMIDT-BELZ, B., A. ZIPF, S. POSLAD & H. LAAMANEN (2002): Location-Based Mobile Tourist Services - First User Experiences; ENTER 2003, International Congress on Tourism and Communications Technologies. Helsinki. Finland - Springer Computer Science. Heidelberg, Berlin.
- STEPHANIDIS, C., A. PARAMYTHIS, M. SFYRAKIS, A. STERGIOU, N. MAOU, A. LEVENTIS, G. PAPAROULIS, and C. KARAGIANNIDIS (2004): Adaptable and Adaptive User Interfaces for Disabled Users in the AVANTI project; 5th International Conference on Intelligence in Services and Networks (IS&N '98), "Technology for Ubiquitous Telecom Services", Antwerp, Belgium.
- UHLIRZ, S. (2001) Cartographic Concepts for UMTS-Location Based Services, In: Proceedings of the 3rd Workshop on Mobile Mapping Technology. Cairo, Egypt.
- WANG, Y., L. YUE, X. CHEN & Y. CHEN (2001): Adaptive Geo-visualisation - An Approach towards the Design of Intelligent Geo-visualisation Systems, Journal of Geographical Sciences, Vol.11 Supplement, pp.1-8.
- WINTER, S. and M. TOMKO (2004): Shifting the Focus in Mobile Maps; In: Morita, T. (Ed.), Joint Workshop on Ubiquitous, Pervasive and Internet Mapping UPIMap2004, Tokyo, pp. 153-165.
- YERNAL, C. M. M. & M. R. C. COULSON (1982): Recreational map Design and Map Use: An Experiment, The Cartographic Journal, Vol. 19, No. 1, pp. 16-27.
- ZIPF, A. (2002): User-Adaptive Maps for Location-Based Services (LBS) for Tourism, in WOEBER, K., A. FREW & M. HITZ (Eds.), Proceedings of the 9th International Conference for Information and Communication Technologies in Tourism, ENTER 2002, Springer, Heidelberg.
- ZIPF, A. and K.F. RICHTER (2002): Using Focus Maps to Ease Map Reading: Developing Smart Applications for Mobile Devices. In: Künstliche Intelligenz (KI). Sonderheft Spatial Cognition. April, 2002. pp. 35-37.
- URL 1: W3C Candidate Recommendation 25 July 2002, http://www.w3.org/TR/css-mobile, accessed on February 16th, 2005.
- URL 2: Cascading Style Sheets FAQ, http://www.blooberry.com/indexdot/css/topics/stylefaq.htm, accessed on: February 26th, 2005.
- URL 3: McGraw Hills Online Learning Centre; highered.mcgraw-hill.com/sites/0072464011/ student_view0/chapter4/glossary.html, accessed on: February 26th, 2005.