The 3D Taipei website features a 4D Choropleth map. 4D Choropleth maps improve users' ability to understand complex information visualization and geovisual analytics by dynamically displaying changing data, such as population change over time.
The 4D Choropleth map on the 3D Taipei website was developed using the Google Earth (GE) API. Because of the planned deprecation of the GE API, the website support team, led by Dr. Sun, is migrating the website from GE to Cesium.
The GE-based 4D Choropleth map uses KML to store time-sequential statistical data. Cesium doesn't support the <timespan> tag yet. However, the Cesium Language (CZML) provides a better solution. The 4D Choropleth map using CZML has a better performance than that using KML in two respects:
4D Choropleth map in Cesium
4D Choropleth map in Google Earth