The image to the immediate right illustrates the use of curved flight lines for large areas such as the McCall glacier in Alaska.
The curved flight lines are constructed from logarithmic-spiral curves such that no portion of any flight line is parallel to any other portion of any other flight line. As such, no two photographs are oriented the same; but all photographs process effectively using Structure-from-Motion (SfM) image processing techniques - that is,the motivation for using curved flght lines is to mitigate the SfM doming (elevation) error.
IGS has pioneered the use of curved flight lines (patent pending) for the capture of digital imagery necessary and sufficient for the production of 3D point cloud models, orthophotography, digital terrain models, and realistic rendered 3D scenes using Structure-from-Motion (SfM) techniques.
Curved flight lines offer a couple distinct, differentiating characteristics that result in direct cost savings and improved accuracy:
1) Minimization of the number of "turn-out" loops required by the use of traditional (straight/parallel) flight lines saves flight time and cost of operation.
2) Mitigation of the systematic SfM doming (elevation) error associated with the accumulation of lens distortion error when traditional (straight/parallel) flight lines are used. This results in improved horizontal and vertical accuracy - even when a minimum of ground control points (GCPs) are used. Also, this characteristic avoids the use of more expensive direct geo-referencing equipment - another direct cost savings.
Our nontraditional (curved) flight mission plans are adaptable for odd-shaped areas - including long narrow corridors such as railroads, highways, pipelines, and/or electric power transmission corridors. The image to the immediate right illustrates a mission plan (curved flight lines) for an electric power transmission corridor segment - complete with turnout loops to accommodate the particular fixed-wing drone used to fly this mission plan. There are no linear or parallel flight line segments in this mission plan.
For smaller areas (such as airports), the non-traditional (non-linear/non-parallel) mission plan can be customized to support aerial data acquisition with the least impact on the operations of the target area. In the image to the immediate left, the original (colored) curved flight lines are shown before any consideration is given to the type of aircraft that may be chosen to fly and collect the required aerial imagery (photography).
The figure to the immediate left illustrates the use of traditional (straight/parallel) flight lines to collect imagery for the same large area (McCall glacier) featured above. Note that numerous turn-out loops were required to maneuver the fixed-wing aircraft into position to occupy successive linear/parallel flight lines. For this actual flight, expensive remote sensing equipment was used (direct geo-referencing) to reach an acceptable level of accuracy in the acquired imagery data.
It's interesting to note that large birds of prey also fly curved flight lines to get to their prey. Use the following link to see an eagle use a log-spiral curved flight line to get to a fish - as long as the link remains available.
Gently Curved, Convergent, Non-traditional (non-linear/non-parallel) Flight Lines
The image to the right (commercial airport) illustrates the curved flight lines (waypoints) after the original mission plan has been adapted for use by a quadcopter drone. Note that there are no turnout loops; because each individual flight line (trajectory) is a continuous circuit; and stationary quadcopter rotations (turns) as well as turnout loops are avoided altogether - saving time, battery power, and money.
Curved flight lines can be customized to a) the type of aircraft being used [including drones] and/or b) pilot preferences to provide the most efficient mission plan - in terms of flight time, fuel requirements, and overall production efficiency. The image to the immediate right depicts a mission plan for a proposed surface mine site - approximately 2 square miles in area. An absolute minimum number of turn-out loops are provided to accommodate the type of aircraft to be used during the aerial data capture operations. There are no linear or parallel flight line segments in this mission plan.
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