In drone survey missions, the choice between photogrammetry and LIDAR depends heavily on the application in which you intend to use. It is important to also consider operational factors, such as cost and complexity. Knowing what outputs you really need will help you make the right decision.
Photogrammetry
In photogrammetry, a drone captures a large number of high-resolution photos over an area. These images overlap such that the same point on the ground is visible in multiple photos and from different vantage points.
The result: a high-resolution 3D reconstruction that contains not only elevation/height information, but also texture, shape, and color for every point on the map, enabling easier interpretation of the resulting 3D point cloud.
Drone systems that use photogrammetry are cost effective and provide outstanding flexibility in terms of where, when, and how you capture 2D and 3D data.
LiDAR
LIDAR, which stands for “light detection and ranging,” has only recently been available in a size for carrying on large drones. A LIDAR sensor sends out pulses of laser light and measures the exact time it takes for these pulses to return as they bounce from the ground. It also measures the intensity of that reflection.
LIDAR uses oscillating mirrors to send out laser pulses in many directions so as to generate a “sheet” of light as the drone moves forward. Through measuring the timing and intensity of the returning pulses, it can provide readings of the terrain and of points on the ground.
Cost Breakdown
Photogrammetry
USD
4-13K - payload
20-30K - whole system
Manned LIDAR
50K+ - payload
150K & up - whole system
UAV LIDAR
65-100K - payload
80-120K - whole system
All above prices in US dollars. To note: an entire high-end photogrammetry system costs between $US 20,000 – 30,000 whereas just the sensor for manned LIDAR typically costs $US 100,000. Lightweight drone LIDAR payloads by themselves run between $US 65,000 and $US 100,000.
Operational Considerations
The difference between photogrammetry and LIDAR grows when considering operational and logistical factors. In order to generate quality results, a LIDAR system requires all of its components to work perfectly in sync. Techniques like ground control points (GCPs), which are useful in photogrammetry to correct issues, are harder to implement with LIDAR.
LIDAR projects require an expert who understands the workflow and details of each subsystem and can recognize consistent and accurate data. In contrast, photogrammetry-based workflows are more forgiving.
The shorter learning curve for drone-based photogrammetry leads to greater flexibility and cost-effectiveness.
While some specific applications might justify the cost and complexity of LIDAR, photogrammetry can meet most of the everyday challenges presented across a range of projects and industries, providing exceptional accuracy and stunningly detailed maps, available on demand and with minimal expertise overhead.
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