An orthophoto is a true-to-scale representation of the Earth’s surface. The term derives from the Greek word ‘orthós’, indicating that orthophotos are taken from an optimally vertical perspective. This is necessary to avoid distortion in this type of engineering survey. In the past, high-resolution photographs were used for this in combination with radar technology. Today, laser scanners are also used here, because their measurement results are particularly precise.
Drones are important tools for creating orthophotos
The first images of the structures on the Earth’s surface to be accessible to the general public were provided by Google Earth. However, they are not sufficient for many purposes. The reasons are their lack of precision combined with the fact that they are only updated at longer intervals. Google mainly uses images taken either from a helicopter or from a hot-air balloon. For some time now, satellite images have been added as well.
We create orthophotos by carrying out drone flights (quadcopters or hexacopters) over the desired areas. Their small size and manoeuvrability ensure that almost any location can be captured with the laser scanner and the cameras from the optimum 90-degree perspective. From the laser scanner measurement data and the images taken by the camera that is also on board, special software calculates raster maps, which are then handed over to the customer as printouts or in digital form. The customer determines the focus of the map material. Examples include existing buildings, the recording of infrastructure or agricultural aspects.
Drones make laser scanning of the Earth’s surface considerably more affordable than survey flights with zeppelins and helicopters. In addition, we can create orthophotos with drones in a much more environmentally friendly way, because they are powered by electric motors. These can be supplied with electricity from renewable sources and emit no greenhouse gases at all, unlike the combustion engines of helicopters.
Orthophotos as a form of engineering surveying
The data obtained by laser scanning the Earth’s surface during overflights is fed into the land cadastre, for example. Here it can be checked whether buildings have been erected as permitted in the building permit.
In addition, the data captured by laser scanner in an orthophoto provides the basis for creating true-to-scale road maps and city maps. It makes it possible to check the width of roads and artificial watercourses from the air. These forms of modern engineering surveying by laser and drone have also become indispensable for drawing up and maintaining municipal land-use plans.
Another aspect must not be forgotten either. Laser scanning of the Earth’s surface provides useful data for planning the future expansion of renewable energy. Using the survey flights and the orthophotos derived from them, it is possible, for example, to identify areas suitable for building solar power plants or dams for hydroelectric power stations.
It is an advantage here that the laser scanner can also directly capture the terrain structures (slope, existing elevations and rivers). Such aspects have a considerable impact on the cost of developing land for solar power plants, reservoirs and any other type of construction.
The orthophotos are derived directly from the 3D point cloud.
This also allows you to derive any floor plans or sections from the 3D scan at any time later on.
