## 2 Materials and Methods
### Data Collection
#### 2.3.1 Prairie Burn Site Testing  
The prairie burn sites were tested first due to the openness of these areas, which provided safe operational practice with the UAS and reduced the risk for tree, bird, and aircraft collisions [59]. Here, the \"default\" data collection variables were tested both before and after the prescribed burn was conducted at the Doak prairie site (Table 6). Following these flights, the images were examined to determine the output of the \"default\" parameters and given atmospheric conditions. Many parameters remained the same across the prairie site testing, such as image overlap (80% \(\times\) 80%), ISO (auto), and zoom (co), flight altitude (121 m or 400 ft AGL), and the number of images outside the study area (1), for example. However, the most critical parameters affecting the initial image quality at the prairie sites were adjusted and tested. Therefore, the shutter speed was increased, and a slightly lower sun angle was examined in the flights surrounding the Hermann burn (* in Table 6).  
Upon examining the preliminary images, it was determined that the shutter speed used for the Hermann burn flights produced higher quality images than those collected from the Doak burn flights. Despite lower sun angles producing longer shadows, the shutter speed increase (1/2500) balanced the exposure and view into shaded areas and, therefore, was used for the data collection surrounding the PWA prairie burn. The atmospheric conditions of the repeat PWA flights varied slightly, but were mostly conducted during peak sun angle times (1100-1600), with clear skie  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Subject** & **Parameter Tested** & **Notes** \\ \hline Sun Angle\({}^{\circ}\) & 48.6\({}^{\circ}\) (1130) & Shadows present in both datasets; slightly longer \\ (Takeoff time) & \& 43.2\({}^{\circ}\) (1315)\({}^{\star}\) & shadows present in Hermann flights \\ Shutter Speed & 1/1600 \& 1/2500* & Slightly overexposed, difficult to see shaded areas \\ \hline \hline \end{tabular}
\end{table}
Table 6: Preliminary data collection parameters tested for first two flights at Doak prairie burn site and second round of flights at Hermann prairie burn site*.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Category** & **Data Collection Parameters** \\ \hline Atmospheric Conditions & Sun angle, brightness (cloud cover), and wind \\ Sensor Settings & Shutter speed, aperture, ISO, and zoom \\ Mission Planning & Flight altitude, overlap/sidelap, and number of \\ images collected outside the study area \\ \hline \hline \end{tabular}
\end{table}
Table 5: Data collection parameters affecting image quality that were tested throughout the data collection phase.  
Repeat flights at the PWA site were flown using the same mission plan, which covered the same 26-acre area in roughly 15 min (not including the manual launch and landing times). The UAS flew a north-to-south pattern at a height of 400 ft AGL and a maximum ground speed of 20 MPH during image passes. While the mission was set to capture an 80% vertical overlap between consecutive images and an 80% lateral overlap between image passes, these overlaps were likely higher given the PPK-triggered camera dimensions were wider than the DJI sensor on which the mission planning software based this percentage.