Presently, commercial drone legislations and regulations are being introduced across different countries around the globe. It is therefore quickly becoming possible for today’s small, medium-size and large companies to integrate these powerful tools into their existing aerial mapping workflows. Although multi-rotors UAVs get most of the attention in the drone world, they are not the only option available. And, in fact for serious aerial mapping you need to consider a fixed-wing drone for plethora of applications, cons such as high cost notwithstanding. So, when choosing a right drone for a particular assignment, one of the first questions you must ask yourself is whether you need a multi-rotor or fixed wing drone. Both multi-rotor and fixed wing drones have a niche of pros and cons that make them better suited for specific uses, so it’s important to comprehend the key differences between both types. Therefore, before purchasing a drone, you need to consider some of the following factors.
Unlike fixed wing, a multi-rotor drone can perform vertical take-offs as well as landings. Additionally, it requires minimal space to take off or land. Indeed, it can also hover mid-flight, maneuver up and around objects for easy survey, mapping, and modeling. This makes multi-propeller drones e.g. a quadcopter ideal for urban area mapping due to the obstruction by buildings and a number of flight legs often required to get enough overlap to make high quality maps. Typically, multi-rotors are fundamentally very inefficient and require a lot of energy just to fight gravity during take-offs and keep them in the air during flight period.
In the current market, multi-rotor aerial vehicles or drones come with a lower price tag as compared to their fixed-wing counterparts albeit there being a far-fetching price variation depending on drone capabilities and functionalities. Nonetheless, you can purchase a professional quadcopter for as low as USD 1,200 whereas a professional fixed-wing drone of similar quality and capability can easily be 10 times as much – or even more. So, practically if you have meagre budget, then you can start with a quadcopter drone e.g. Phantom 4 and later upgrade to fixed wing such as eBee X or SQ.
Unlike fixed-wing drones, multi-rotor drones don’t require the surface area or wingspan. Therefore, they are more compact than fixed-wing hence easier to carry or transport. Hexacopters and octocopters which are larger in size can also be folded down to a portable size for easy transportation.
Heavy-rift Multi-rotor drones or aerial vehicles such as an hexacopter generally support more weight onboard due to their compact design whilst maintaining stability during a flight. However, this means that a larger, more expensive drone will be needed if one intends to carry significant payloads such as pesticides for spraying crops, drugs etc. or other camera rigs as need be. But the flight time of such drones is often shorter!
One limitation of multi-rotor drones is the flight range on a single battery. Unlike fixed drone such as eBee SQ which can fly continuously for approximately 1 hour, most multi-rotor drones can fly for shorter period of time (about 20 - 30 minutes) in ideal weather conditions before it returns home for battery replacement. So, if you need to survey and map a large area say, 20,000 hectares using a quadcopter, it will take you several days to accomplish the task. Alternatively, you can offset this downside by purchasing additional batteries for replacement – this option will not only add cost to your project but also consumes extra time and energy. Even so, multi-rotors are unsuitable for large scale aerial mapping, long endurance monitoring and long-distance inspection such as pipelines, railway lines, roads and power lines.
The aerodynamics of multi-rotor drone or UAV leaves them more vulnerable and susceptible to wind hence become less stable especially when wind speed is high (>5m/s). This therefore means that for projects and applications where high winds are expected, you may be required to acquire a larger, heavier, more stable and more expensive multi-rotor aerial vehicle. Furthermore, Fixed-wing drones as opposed to ‘multi-rotary wing’, i.e. quadcopters, use a wing like a normal aeroplane to provide the up-lift rather than vertical lift rotors. As a result, they only need to use energy for forward movement and not hold themselves up in the air (as the case in quadcopter), hence are much more efficient in battery usage and stable when flying.