Warning: flying very low (at or below 40m above the highest canopy) may not yield the desired results. The practice recommended below may improve the chances that your data can be processed, but it is not a guarantee. For the most reliable results we recommend flying at altitudes at or above 40m, and always with at least 75% overlap in both the along-track and cross-track directions.
If your applications require that you fly at low altitudes, it is necessary to fly over the same area from at least two separate altitudes. We recommend flying at the altitude for your desired output resolution, and then also flying at 1.5-2 times that altitude. Follow the data collection guidelines for the flights at each altitude - 75% along-track and 75% cross-track overlap, and flight plans that cover the entire area uniformly. Take an image of a calibrated reflectance panel before and after each individual flight.
For example, if you would like to fly at 30 meters over your field, conduct as many flights as necessary to cover the area of interest at 30 meters, and then fly the entire area at 45-60 meters. We have found this process significantly reduces processing time for low altitude flights, improves the reliability of the results, and the final mosaic maintains the output resolution of the lower flight.