Light Detection and Ranging (LIDAR) is an airborne mapping technique, which uses a laser to measure the distance between the aircraft and the ground.
Environment Agency Open data includes 'digital elevation data derived from surveys carried out by the Environment Agency's specialist remote sensing team.'
We often have GIS polygon data to represent building 'footprints'. Using LIDAR data we can determine an average height for buildings, which aids in creating 3D maps that display building heights.