4.3 Technical Framework Requirements

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4.3 Technical Framework Requirements

The OpenLayers demo controls.html³⁵ serves as the basis for the implemention of the animated zooming feature. Adaptations are possible. The following layers (along with their map sources) are used:

• WMS-BaseLayer (default): http://labs.metacarta.com/wms/vmap0
• WMS Untiled-BaseLayer: http://labs.metacarta.com/wms/vmap0
• Image-BaseLayer: http://earthtrends.wri.org/images/maps/4_m_citylights_lg.gif
• WMS-Overlay: http://www2.dmsolutions.ca/cgi-bin/mswms_gmap

Expandability

The implementation takes into account a possible expandability of the application at a later date. In particular, the should-have criteria outlined in Section 3.3.3 are to be integrated into the conceptualized animated zooming feature with as little effort as possible. The animated panning feature³⁶ developed by OpenLayers (currently still in review stage) serves as a component for the implementation of the automatic zoom animation. The algorithm for the time-dependent calculation of force movement curves (rapid start, damped finish) is to be extended in such a way that it can used for the zoom animation process. A combination of pan and zoom animation processes should also be possible.

Because of the different types of layers (see Section 3.4.2) supported by OpenLayers an individual treatment of each different scale action is required. Identical source code can be stored in the base class Layer.js. Layer-specific zoom activity can be treated with individual (overwritten) methods so that only the new layer class has to be adapted during the integration of new layer types. Changes in the key functions is not required, ensuring a fairly easy expandability of the animated zooming feature.

4.3 Technical Framework Requirements

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