Flight Planning

Flight planning is always the responsibility of the acquisition contractor. Flight planning for LiDAR will vary greatly depending on the sensor utilized for the acquisition. Parameters such as flying height, ground speed, scan rate, scan angle, etc will be different for each sensor. The contractor’s flight plan should be evaluated to ensure there is sufficient swath overlap given the sensor’s scanning mechanism and project accuracy specifications. Typically, 10% overlap between swaths is the minimum requirement for an airborne LIDAR collect. However, most LiDAR flights are conducted with 30% overlap, and those that require higher pulse density in vegetated areas are often flown with 55% overlap. A higher percentage of overlap may be beneficial in an area with dense vegetation as there will be more look angles from the sensor to the ground at any given points. The result would be a lower point density requirement in an individual swath with the overlap accounting for an overall higher point density on the project. Depending on the scanning pattern, data from the extreme edges of the swath may be unusable due to geometric nature of the scan pattern. Table 1-1 below shows the operational parameters for a sample LiDAR project for an Optech ALTM 3100 system. The LiDAR flight planning process is mostly automated after entering basic information such as point density, overlap requirements, and scan angles. Trajectories are planned for each flight line. Furthermore, modern Flight Management Systems (FMS) enable the pilot to fly these trajectories with close tolerance. LiDAR sensors are actively acquiring data throughout the entire flight which requires the aircraft to be consistently ‘on-line’ to ensure full coverage. Additionally, sensor operators are often able to view the acquisition in real time and assess areas where voids or sensor anomalies may be present during the flight. While LiDAR sensors also have some forms of stabilization, the roll, pitch and yaw of the aircraft still depends upon wind conditions. Regardless of sensor to be used, flight planning also includes the assessment of military and other controlled air space where special permits may be required. Aviation Sectional Charts are often used to determine flight restrictions and controlled airspace when planning flight lines.