Having determined your area of interest, established GCPs and defined flight parameters, you are now set to fly your UAV. If the mission has been properly planned, this should be pretty easy! The points below are important lessons that were learnt within the STARS project concerning UAV flights in smallholder agricultural areas in SSA and Asia. Taking note of these may help you in achieving successful missions.
- Permission to fly: depending on your jurisdiction and the height at which you intend to fly, you may need permission/clearance from your national aviation authority to fly your UAV. In Mexico for instance, flights above 120 m (with UAVs heavier than 2 kg) require authorization from air traffic regulators. You need to also take note of the presence of sprayer aircrafts and other low altitude flying machines.
- Flight time: the best time to operate UAVs in high temperature areas (e.g. STARS’ West African sites of Mali and Northern Nigeria) is between 9.00am and 11.00 am. Exposure to high temperatures causes an over- heating of the camera and the whole unit. SenseFly eBee was found to be particularly vulnerable to high temperatures, possibly due to its outer black color. One approach that can reduce the effect of heating is to limit exposure of the UAV only to the actual flight time. In other words, it is not advisable to excessively expose the unit to sunlight prior to the flight. You may also want to consider covering the black portion with a material that reduces its susceptibility to heating. This practice, however, may be seen as you forfeiting your warranty.
- Battery: It is a good practice not to completely exhaust the UAV’s battery during flight campaigns. For the eBee, there is an 80% battery usage limit which when adhered to can prolong battery life. It is advisable to factor this into your planning
- Be aware of possible bird attacks on the UAV
- It is important to clear SD before each flight campaign
- Mounted cameras sometimes switch to video mode as a result of the UAV shaking during landing or in strong windy conditions. It is, therefore, important to ensure that the camera is firmly fixed to record only still pictures
- Flying is preferred during the morning because wind speeds are often higher in the afternoon and cloud cover is also increased.
- Flying around the time of solar noon should be avoided because of specular reflectance from the land surface, especially from wet areas, such as flooded rice fields but also from other land cover types.