No two mapping projects would be exactly the same. The underlying difference lies in the cartographic techniques, projection mechanism, terrain and topography of the region to be mapped and the use of equipment. These days’ drones are increasingly being used for aerial mapping to enhance precision and attempt to nullify error margins. However, even with drones, there are some challenges and not all camera-mounted drones can be used for aerial mapping. Therefore selecting the right drone according to the mapping requirements is important.
There are many regions that require updated mapping as it has been decades since they were last mapped. And so, the geographic and spatial data of these regions does not take into account the variations in the past decades. This renders old maps obsolete for modern professional requirements.
Up-to-date mapping is essential to keep track of the land and gain new insights of the changes that took place.
Mapping projects undertaken in remote and inaccessible islands could serve as an example in outlining the various difficulties and challenges in mapping.
The level of detail of satellite imagery is inadequate and aircrafts equipped with high-resolution surveying equipment are too expensive to operate in isolated locations.
These drawbacks could be overcome by using drones, but they have their own operational constraints or hurdles.
Let’s have a look at the major challenges which we have to grapple with while selecting drones for mapping.
Five Key Points to remember
Take Off: As the most important part of a flight, it is absolutely necessary to find a suitable location from which to launch and recover the drone. Since multicopters( drones that have 4 rotors and a functionality similar to helicopters) and hybrid drones( a hybrid between airplane-like fixed drone and multicopter) can fly smoothly helicopters, they can take off with relative flexibility.
But, in the case of fixed-wing drones, selecting a suitable location is very difficult, as it requires a vast stretch of open land. Multicopters and hybrid drones offer an advantage: they can land vertically and occupy much less space.
The area to be mapped: The time that is taken in mapping and the cost incurred is directly proportional to the area that is to be mapped. The rotors of a multicopter drone consume a lot of energy and that is why they are suitable for small mapping projects. On the other hand, fixed wing and hybrid drones can stay in the air for a long time fly faster and map with more efficiency. This makes fixed wings and hybrid drones desirable when large landmass has to be mapped.
Accessibility: Isolated and remote areas are the most difficult to map and ensuring accuracy in mapping is even more challenging. Since ground controls are not viable in these locations, drones equipped with post-processed kinematic (PPK) module are used as the only alternative available. Just like real-time kinematics (RTK), this module generates geotags of the photos at a higher-than-usual precision. The increased accuracy of the geotags also increases the accuracy of the resulting model, and this means that there is no need to map ground points.
In rugged terrain and areas covered with dense forests, it is impossible to set up a ground control point anywhere. Hence, the PPK model is used in this situation.
Transportation: In order to tap the complete potential of the drone, it should be used at regular intervals and the movability should not be troublesome. As per different projects, the system must be suitable for shipping as air freight, fit easily in a small car and be easy to carry around in the field. For portability and ease-of-handling, backpack is also used.
Wind: Wind resistance is a major obstacle in the path of drone deployment and its maneuverability. A drone with a higher wind resistance can be deployed more frequently, increasing the possibility to execute the project on time.
Multicopters have good wind resistance when they take off. Drones with in-built wings have higher cruising speeds, enabling them to fly against the wind. Hybrid drones with minimum four propellers have high wind resistance and stability during take-off and landing and can withstand the pressure of the wind.