Professional survey and mapping drones are increasingly disrupting a range of industries due to their ability to gather rich location information much faster than terrestrial methods. However, because this is a new field of technology, it can be hard to judge the performance of a drone based on simplified tech specs. One of the most confusing of these is flight time, because it’s often considered as an independent factor, when really—if your aim is to capture high-quality data fast—it’s not.
Breaking down the drone flight-time matrix
Even if the flight time is “the longest around,” can the drone collect reliable, high-accuracy data in a single, or just a few flights with minimal set-up time expense?
In fact, a lot of companies are finding out that once they start using drones, more opportunities and more project offers featuring both large areas and challenging conditions emerge. For anyone serious about the benefits of drone surveying and mapping, the right choice of technology brings a competitive business advantage amidst rising drone data demands.
Drone flight time in context
Payload
Using a heavier payload reduces flight time. However, even though the flight time is shorter with a heavier payload, the quality of that payload might allow you to fly higher for the same resolution and accuracy. So you would capture more ground per image and get your job done faster.
For example, WingtraOne can carry a range of different payloads, and according to the payload weight, the flight time varies slightly. However, even if you fly with a heavier RX1R II camera, the coverage you get might be larger depending on the mission. At 3 cm (1.2 in) / px GSD with the RX1R II, you get up to 52 min flight time compared to 59 min with the QX1, but you can cover 400 ha (988 ac), compared to 310 ha (766 ac) with QX1.
Flight time and coverage: different payloads, same 3 cm (1.2 in) GSD*
WingtraOne + RX1R II & PPK
52 minutes covers 400 ha (990 ac)
WingtraOne + QX1
59 minutes covers 310 ha (760 ac)
Altitude above sea level
With altitude increase comes thinner air, which requires more force and power to generate lift. Drones typically don’t fly at super high (> 5000 m/ 16,000 ft above mean sea level), altitudes because it’s so expensive for the battery. Add to this that the speed at which they must fly increases, and typical payloads can’t handle this. For a payload that can, the coverage per shot compensates for the lost flight time and, note that (!) this even allows more coverage than at sea level with a capable payload. In other words, speed compensates for some part of the extra battery expense, so you will still cover a good amount of ground.
Flight time and altitude: different altitudes, same GSD, who covers more?*
WingtraOne + RX1R II & PPK
2000 m (6560 ft) AMSL
WingtraOne + QX1
Sea level
Vertical hover vs. cruise mode
If we take the WingtraOne as an example again, we know that this VTOL drone uses significantly more energy while hovering, thus the more you hover, the less battery you have for the actual mission. This means that the transition altitude significantly affects flight time: higher transition altitude equals reduced flight time.
Wind
Temperature
A better question: What's the coverage per flight?
Flight height
Sensor size
Side overlap
In the end, more important than just looking at flight time is making sure you select the right camera configuration. In many cases, the right camera and settings can get your data captured faster even if the flight time might seem shorter!
Getting the job done
At the end of the day, it is not just about flight time, but rather about how fast you can get the required data for a given area. Beyond flight time, the keys to reducing your overall drone mapping job time are reliability over repeat surveys, and overall ease-of-use in the field.
For large areas, you need a drone that can fly time after time and require minimal maintenance or technical support, as highlighted in this case study. A VTOL design can also offer a lot of time saved looking for a large area to launch and land a fixed-wing, with 14x faster data capture than a quadcopter. Plus a well-integrated PPK system will reduce massive time expense laying ground control points over larger areas. Finally, the setup needs to be intuitive, taking just minutes and requiring minimal training.
Beyond flight time, these are the considerations that will get your job done fast, at the quality you need, with the fewest headaches possible.
*Flight time calculations based on optimal conditions: 20 m (65 ft) transition altitude, 1 m/s wind, 15 C air temp, 60% side overlap.
