Part 4 Front to end# Front to end libraries, includeing LeafletJS, OpenLayers and Cesium. 1. Leaflet lightweight WebGIS front-end class library 1.1. Introduction to Leaflet 1.2. Custom callout icon 1.3. Use GeoJSON and Leaflet 1.4. Interactive Choropleth Map 1.5. Layer group and layer control 1.6. Zoom Level 1.7. Use WMS with TMS services 1.8. Use the map panes 2. OpenLayers class library 2.1. Intruduction for OpenLayers 3. Cesium front-end 3D GIS class library