3.3 Requirements Analysis

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3.3 Requirements Analysis

One of the more surprising observations in Section 3.1.4 is the extraordinary continuous zooming feature of p.mapper. OpenLayers on the other hand is convincing in almost all other areas, and in addition has one of the most active communities in the Free web mapping area. Furthermore, using the new term Smart Map Browsing (see Section 3.2) as a guide, there is great development potential for OpenLayers and animated zoom processes. A zoom feature similar to the one featured in p.mapper would be an ideal addition to OpenLayers.

Based on the reasons stated above, the Free web mapping application OpenLayers supplemented with a novel add-on animated zooming feature was selected for the practical part of this thesis. This section details the exact requirements for this type of add-on feature.

3.3.1 Purpose

The purpose of the practical thesis portion is to implement the Smart Map Browsing feature animated zooming into the Free mapping application OpenLayers.

The main purpose of the extension is to assist during navigation, so as to ensure the user's orientation during the zoom process.
Note: Empirical measurements will not be conducted, therefore a measureable enhancement is not possible. However, the definition of Smart Map Browsing implies that this extension would have a positive effect on usability. In comparison to non-animated zoom processes (whereby the map »jumps« into the desired zoom level), an animated continuous zoom process would noticeably improve the user's orientation, which would likely also lead to greater acceptance by the community. A general consensus regarding the attractivness of this extension is evidenced by the mailing list discussions on animated zooming.

3.3.2 Must-Have Criteria

The functionality of an application (as seen from the user's point of view) is described by the following Must-Have requirements:

1. It should be possible to freely move the zoom slider on the zoom bar by holding down the left mouse key. This means implementing the following application scenarios:
   • a) The selected view of the main map is scaled on-the-fly by moving the zoom slider.
   • b) During ZoomIn the map is scaled by an enlargement of visible tiles. Depending on the difference in zoom levels, the tile bitmap graphics will be somewhat or significantly more pixelated.
   • c) During ZoomOut the main map is initially scaled by decreasing the size of visible tiles. The resulting white border (around the smaller map) should be filled in such a way that the user is always viewing a completely filled-in map surface.

     The redrawn map surface is scaled relative to the tiles of the original map selection.

   • d) If several overlays are activated, they are scaled together with the selected base layer. Note that items such as symbols and letters will also be scaled up or down as part of this process.
   • e) The overview map contains a marker, whose size adjusts along with the zoom process (simultaneously with the modifications to the main map). The marker always shows the current area of the main map.
2. As soon as the user selects the desired zoom level (by releasing the left mouse key), the hitherto scaled bitmap tiles (along with all activated overlays) are redrawn.

3.3.3 Should-Have Criteria

The should-have criteria for the animated zooming feature are defined as follows:

1. Full animated zooming support for all layer types available in OpenLayers.
2. Zoom Animation with Zoom Bar (buttons)
   • a) On clicking the + or - button at the end of the zoom bar, the map is zoomed in or out by one level.
   • b) On clicking at a specific point on the zoom bar, the map is zoomed to the level indicated by the pointer.
3. Double-click Zoom Animation
   • a) When a user double-clicks on the map, the map will be zoomed in by one zoom level. The geographic position of where the double-click ocurred is now the new centre of the scaled map view.
   • b) With double-click animation the zoom and pan processes are combined. This requires only an animation of the zoom process; the panning occurs before zooming without animation.
4. Zoom Animation with Mousewheel
   • a) By turning the mouse wheel up (ie. away from the user) or down (ie. towards the user), the user is able to zoom into/out of the map by exactly one zoom level.
   • b) As per the Smart Map Browsing definition of mouse wheel zooming properties (see Section 3.2.2), zooming per mouse wheel is described as follows: »The geographic position below the cursor at the time of mouse wheel operation remains at the same pixel position after the zoom has been completed.«
5. Zoom Animation with Zoom Box
   • a)Once the user has pulled up a map area and released the left mouse key, the map is zoomed to a level that displays this selected area.
   • b) Using the zoom box tool to click on the map (without pulling the zoom box into the map) results in a zoom action equal to one zoom level. The geographic position of where the click occured now becomes the new center point of the map.
   • c) In zoom box animation zooming and panning processes are combined. Only an animation of zoom processes is required however; panning occurs before zooming without animation.
6. Zoom Animation with Keyboard
   • a) Pressing the + or - key results in a one level zoom increase/decrease.

The following is valid for each zoom animation:
The animated zoom process occurs automatically within a defined time period. The zoom slider moves in sync with the animation until the desired position (up or down) is reached. Once the map is at its highest/lowest zoom level, no additional zoom-out or zoom-in animation is possible. During the zoom animation the marker in the overview map adjusts itself continuously to the section of the main map. As long as the zooming animation is active, no additional zoom processes can be activated.

3.3 Requirements Analysis

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