What is the difference between a topographic survey and a Digital Terrain Model?

A topographic survey is the field data collection process — a surveyor captures ground levels, features and contextual information using GPS and total station equipment. A Digital Terrain Model (DTM) is a deliverable produced from that data — a mathematical model of the bare earth surface, with vegetation and above-ground structures removed. A Digital Surface Model (DSM) includes vegetation and structure heights. Both DTMs and DSMs can be produced from topographic survey or UAV LiDAR data. Environmental consultancies and flood risk engineers commonly require DTMs as the primary deliverable for flood modelling and drainage design. We produce both, and we will confirm which is required for your project at the time of scoping.