An Evaluation of the Effects of UAS Flight Parameters on Digital Aerial Photogrammetry Processing and Dense-Cloud Production Quality in a Scots Pine Forest

Abstract

The application of unmanned aerial systems (UAS) in forest research includes a wide range of equipment, systems, and flight settings, creating a need for enhancing data acquisition efficiency and quality. Thus, we assessed the effects of flying altitude and lateral and longitudinal overlaps on digital aerial photogrammetry (DAP) processing and the ability of its products to provide point clouds for forestry inventory. For this, we used 18 combinations of flight settings for data acquisition, and a nationwide airborne laser scanning (ALS) dataset as reference data. Linear regression was applied for modeling DAP quality indicators and model fitting quality as the function of flight settings; equivalence tests compared DAP- and ALS-products. Most of DAP-Digital Terrain Models (DTM) showed a moderate to high agreement (R2 > 0.70) when fitted to ALS-based models; nine models had a regression slope within the 1% region of equivalence. The best DAP-Canopy Height Model (CHM) was generated using ALS-DTM with an R2 = 0.42 when compared with ALS-CHM, indicating reduced similarity. Altogether, our results suggest that the optimal combination of flight settings should include a 90% lateral overlap, a 70% longitudinal overlap, and a minimum altitude of 120 m above ground level, independent of the availability of an ALS-derived DTM for height normalization. We also provided insights into the effects of flight settings on DAP outputs for future applications in similar forest stands, emphasizing the benefits of overlaps for comprehensive scene reconstruction and altitude for canopy surface detection.

Unmanned aerial system‐based high‐throughput phenotyping for plant breeding

“…With the same image overlap, a high flight altitude can cover a larger area, whereas lower flight altitude can cover a small area with high spatial image resolution. Therefore, an operator must find optimum weather and flight conditions when planning UAS missions (de Lima et al, 2021). Based on our experience with UAS missions under various conditions, we establish the recommended conditions for mission planning: Some of the commonly used software and applications to plan flight missions and control the drones for aerial mapping are Litchi (Vc Technology Ltd.), Pix4D capture (Pix4D), DroneDeploy (DroneDeploy), and DJI GS PRO (SZ DJI Technology Co.).…”

“…With the same image overlap, a high flight altitude can cover a larger area, whereas lower flight altitude can cover a small area with high spatial image resolution. Therefore, an operator must find optimum weather and flight conditions when planning UAS missions (de Lima et al., 2021). Based on our experience with UAS missions under various conditions, we establish the recommended conditions for mission planning: (a) prepare sufficient, fully charged batteries including one or two extra; (b) set up the optimum flight altitude and overlap according to the required image resolution and field size; (c) conduct UAS missions under low wind speed (<15 mph) and clear sky; and (d) select a bright‐colored platform and sensor, if possible, avoid overheating.…”

Measuring Annual Sedimentation through High Accuracy UAV-Photogrammetry Data and Comparison with RUSLE and PESERA Erosion Models

“…The automated flight plan led to consistent flight paths repeated on every flight. The minimum image overlap and the maximum forward and side overlap reached 75%, as other researchers also indicated in forestry areas [77][78][79]. Flight planning and operation were performed on DJI GS PRO.…”

Analysis of Human Factors in Typical Accident Tests of Certain Type Flight Simulator

“…It should use continuous objective measurement methods. Measurements of mental load at each stage are used to estimate peak load and thus to evaluate overall load, so subjective evaluation methods are now usually used in combination with physiological measurements [16][17][18]. Physiological measurement technologies reflect changes in pilots' workload levels.…”