Making an animation with image layers

When working with geographic information, its geometrical representation within the space is not the only important thing. Day by day time is becoming a new and important dimension to take into account.

This way, visualizations must show how data changes over time: city population, country frontiers, roads built, and so on.

There are many solutions to animate the data evolution through time but, as always, we work with web technologies, there are two groups: the solutions based on the server side and those based on the client side.

For server-side solutions, we can find the TIME parameter in the WMS and WFS standards. It allows us to request for raster or vector data in a specific time or within a range.

Server solutions means the client must request the server every time we want to show the data for a different interval.

For the client side, a simple solution is to have in the memory all the data, and only show those that correspond to the interval we are...