Our solutions for Unmanned Autonomous Vehicle (UAV) aerial (drone) mapping systems range from entry level photogrammetry “guest” systems through GeoCue-designed survey grade RIEGL-based 3D Imaging Systems (3DIS®). While some clients are very experienced in aerial mapping and know just what they want, others are just now augmenting ground-based techniques and wonder how to choose a UAV mapping system.
A guest post by Lewis Graham, Founder and CTO of GeoCue.
#1 What is Your Overall Goal?
The number one consideration is “what do you need to accomplish?” While I cannot address every scenario we have encountered, the problem statements might look similar to this list:
- We have a bare earth mine site with known control marks. We just need to perform periodic volumetric analysis.
- We are a services firm who are going to start out with non-vegetated mapping at sites where we have no a priori ground control
- We are an industrial operator who need to do topo and volumetrics on a variety of sites, many of which are vegetated
- We are a land developer who need to collect planning topographic data (“topos”). We have no other mapping needs
- We are a mapping services firm who will do drone mapping in a wide variety of applications ranging from topographic mapping to wire collection
- We are a survey services firm who will be doing high network accuracy, high precision data collects for demanding customers such as Departments of Transportation
The choices in technology range from a camera system with no augmented positioning to a full True View LIDAR/Camera (3D Imaging System). Of course, pricing ranges from sub $10,000 up to $200,000 or more, depending on the system.
Generally, their are three choices in drone sensor survey/mapping technology:
Photogrammetry – a three dimensional (3D) point cloud is derived from overlapping images
LIDAR – a 3D point cloud is directly collected using a ranging laser scanner
3DIS® – a 3D point cloud is directly collected using a ranging laser scanner. Each point of the cloud is colorized using cameras calibrated and synchronized with the laser scanner
Photogrammetry Approach
Photogrammetry systems are the least expensive but not necessarily the easiest to post-process. No matter what you might hear in the popular hype, photogrammetry systems basically work with bare earth collections. A photogrammetry system requires that the same “object point” (e.g. a spot on the ground) be seen from multiple camera positions. Due to this geometry constraint, these systems will not collect:
- Ground beneath any sort of overhead vegetation canopy (so useless for operations such as estimating for grubbing, initial topo surveys and so forth)
- Any sort of overhead or thin linear structure such as poles, wires, piping, conveyors, railroad tracks and so forth
- Areas with “urban canyons” such as closely spaced buildings, containers and so forth.
LIDAR Approach
Laser scanners “image” object points with a single laser pulse. This pulse (especially from UAV altitudes) is rather small in diameter (several 10’s of centimeters) and thus can penetrate through gaps in tree canopy, spaces between buildings and so forth.
By combining position and orientation information from the UAV-carried Position and Orientation System (POS) with range data from the laser scanner, a high accuracy 3D point can be discerned from a single return pulse. This is powerful stuff!!
For the complete article on how to choose a UAV mapping system CLICK HERE.
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How to Choose
