We use drones (small unmanned helicopters and planes) for aerial surveys and mapping.
This is achieved by combining low altitude aerial photography with geometrically calibrated cameras and a technique called photogrammetry. With these pictures we create 3D digital elevation and terrain models as well as orthophoto mosaics.
First of all drones are very quick to deploy as they can even be flown with cloud cover.
The results are also better, both in resolution and accuracy, as the pictures are taken much lower than conventional aerial photography.
The individual images can be adjusted for the elevations in the terrain corrected for color differences due to changing weather conditions.
All the pictures can then be joined into a seamless orthophoto mosaic.
As the image is fully to scale it can then be imported directly in a CAD or GIS as a backdrop and used for measuring or mapping.