...
Terrain Follow without a rangefinder uses global terrain data to direct the elevation adjustments of the drone based on the information it receives from the terrain tiles that are downloaded. A conversion occurs based on local position in relation to the reference point, which takes into account the Earth’s curvature during this process.
As a result of this process, this form of terrain follow is only considering the geography of the terrain on a larger scale, and often may not include structures that are present, though this isn’t always the case.
When using terrain follow in this fashion, the drone pauses for a few seconds on the first waypoint of each turn, but will swing into the next line of the survey as usual when motion resumes. This currently is a byproduct of the conversion process that occurs.
Terrain follow with a rangefinder is actually known as surface tracking. As the name implies, it functions based on the active readings that the rangefinder gets from the ground and classifies it a local Terrain data, which then sends corrections to the GPS to adjust height based on the object detected.
...