Using photogrammetry it is possible to monitor the progress of construction in real time.
It is an essential technique for a correct elaboration of cartography, whether topographic, thematic or cadastral.
Photogrammetry show us the geometric characteristic of an object or surface, obtaining a faithful reconstruction thanks to the large number of images taken and their repetition. This repeated information is what allows us to extract its structure.
Flight planning software is needed to calculate the shooting sequences based on the expected position of the drone, its height and the desired overlap.
Once the images are obtained, another software is used to process them to calculate the XYZ position of millions of points. These will be used to generate 3D reconstructions in the form of polygons, point clouds, or orthophotos.
Until the recent appearance of drones, aerial photogrammetry was performed with satellite images from helicopters or light aircraft.
There is no single solution for all projects, each of them presents a series of advantages and disadvantages:
- Helicopters: Although they can offer good resolution (20/40 cm/pixel), both operation and processing involve high costs.
- Airplanes: They offer a similar resolution to helicopters, and the operation costs are less expensive than the previous ones, but even so, the cost of processing is very high, even reaching thousands of euros for a single project.
- Satellite: Despite not being an excessively expensive technology, they have drawbacks, such as a very low resolution for this type of work (1m per pixel), in addition to needing revisit time and the possible presence of clouds.
- Drones: With the arrival of UAS, the speed of the photogrammetry process is improved, since in a short time we can obtain a fully processed map, with very low costs and with greater control of the final result.