1 Human Computer Interaction Week 12 Information Search & Visualization

2 What is the best way to present large scale graphical information on a computer display screen? HCI Problem

3 Solution 1 Uniformly scale the entire map onto the size of the display screen. Disadvantage: detail information cannot be read from the screen.

4 Solution 2 Show a small section of the map at a time on the screen. Disadvantage: Extremely difficult to navigate around the map.

5 Non distortion-Oriented Presentation Two non distortion techniques commonly used in the presentation of textual information are scrolling and paging. Examples: Dual screen system Split screen system

6 Distortion-Oriented Presentation Distortion-oriented presentation techniques involve the visual modification of the displayed data. Examples: Bifocal Display system Fisheye View system

7 Dual Screen System Needs two computer screens. The first screen presents all information and the second presents the details.

8 Split Screen System (1) A variation of the dual screen systems. The screen is divided in two separate regions: one region displays a small section of the map in detail and another displays the demagnified map with the area displayed in the other region highlighted.

9 Split Screen System (2) Advantages: Only one monitor is required. Useful if the size of the map is between times the size of the screen. Disadvantages: Users still have to swap between sections of the display screen to maintain good context. Reduced area of detailed display on the screen. A large display monitor is required.

10 Bifocal Display (1) Is introduced by Spence and Apperley in The bending of graphics information so as to create a bird’s eye view of the whole entity, and at the same time, allow the user to concentrate on one area in detail.

11 Bifocal Display (2)

12 Bifocal Display (3)

13 Bifocal Display (4)

14 Bifocal Display (5) Advantages: Only one monitor is required. Practical if the size of the map is up to 30 times the size of the screen. Users maintain context of the entire map at all times.

15 Bifocal Display (6) Disadvantages: Reduced area of detailed display on the screen. Abrupt change of display at the boundaries of different regions. Extra computation time required to generate the bifocal image.

16 Fisheye View System (1) Is introduced by Furnas in Suppresses some parts of the information space so that the remaining parts can be seen in detail.

17 Fisheye View System (2) Advantages: Only one monitor is required. Practical if the size of the map is less than 20 times the size of the display screen. Users maintain context of the entire map at all times.

18 Fisheye View System (3) Disadvantages: Reduced area of detailed display on the screen. Most demanding on computation time to generate the fisheye image. The image tends to be severely distorted at the extreme ends of the map.

19 Further Reading Shneiderman, B. 1998, Designing the User Interface, Chapter 15, pp