Aerial imaging drone developer Sensefly has said that the millimetre accuracy of the latest equipment means that drones could be used for construction surveying applications.
According to Sensefly, professional drones are commonly used today in land surveying and GIS applications but it is unusual to see them employed on construction sites for highly accurate survey work.
Sensefly has used its Exom quadcoptor to create 3D point clouds with a global precision comparable to that of a total station survey.
“This degree of absolute accuracy from a drone is unparalleled and positions the Exom as a surveying instrument that is comparable in performance to standard total stations,” said Sensefly co-founder Andrea Halter. “These results were due, in part, to the high 38MP resolution and sharpness of the flight’s images, captured by the main camera inside the Triple View head. Add to this image quality the ability to operate close to the terrain and the introduction of highly precise ground controls and you have a recipe for exceptionally accurate 3D data.”
The two drones flew separate survey missions at an altitude of 14m above the site, achieving an average ground sampling distance (GSD) of 2.2mm. All the flights were completed using the drone’s Interactive Screenfly flight mode, whereby the UAV is controlled using a handheld Screenfly controller connected to flight planning and control software.
This flight mode’s cruise control feature, combined with its auto-trigger function, enabled each of the drones to survey the 1,100m2 site in a single flight. Meanwhile the live on-screen feedback from the drone’s five different navcams and ultrasonic proximity sensors helped the operator ensure that no contact was made with either the on-site crane or any the trees surrounding the complex site.
Halter is already looking ahead to what the Exom drones might be capable of. “This project’s flights took place at 14m above the ground, but with the distance lock feature we are able to safely fly just 4m away, so it isn’t unrealistic to think that the accuracy we achieved could be improved still further.”