Sabre Sky3d UAV LiDAR system testing
by Stephen Ball Director and Founder of Sabre
The Sky3d UAV LiDAR system is a small airborne laser scanning system which generates High definition direct measurement point clouds of terrain and structures. It comprises of the following senor technologies (IMU/GPS/Laser) along with our in-house integration software which time tags positioning information with Laser sensors to generate fully geo referenced point clouds.
Why airborne LiDAR? As you may be aware of, photogrammetry plays a big part in UAV mapping missions nowadays due to its low weigh, low cost and due to the rapid development and access of photogrammetry algorithms and ready to use software packages.
The airborne LiDAR doesn’t replace the camera in any way however brings to the table further benefits in gaining data which cannot be obtained by Camera systems. LiDAR is a major benefit in mapping forest areas for tree height and yield estimations, shoreline cliff areas, power line vegetation and sag analysis, corridor mapping for infrastructure as well as general quantity mapping of quarries and stock piles. LiDAR gives you the ability to penetrate below shrubs and trees which allow you to slice the surface to create accurate models of the terrain below.
Further to this, a fully geo-referenced laser or camera system takes away any need to obtain ground control to process accurate point cloud data.
Sabre’s goal Overview
The system was first developed and tested as a survey grade mobile mapping system which is called Sabre-scan, utilising the same functionality and sensor technology, Sabre’s next task was to convert the ground based Sabre scan mobile mapping system in to an easy to use airborne mapping system.
Main problems going airborne was of coarse weight, weighing in at around 12kg the system was just far too heavy to be flown on a small unmanned aircraft. We wanted to deploy below the sub 20kg category weight limit in the UK so we started to scale down the chassis, covers, GPS and IMU equipment to save every gram of weight.
We came up with an integration package weighing around 3kg which includes the IMU sensor, GPS,GLONASS cards, Duel Antennas, RTK radio and embedded pc. This part of the LiDAR system provides high accuracy position data which utilises either RTK base station data form your own static GPS base station on site or do a post processing activity which takes in a local VRS or correction service data to enhance the accuracy of the GPS position.
Further to this you need to add a laser scanning head, we can integrate many off the shelf laser heads on the market however there are very few on the market which are light enough and with a good accuracy in which you want to use for mapping. The Sky3D utilises the following laser scanners:
Faro focus S120 and X330 (2mm accuracy phased based scanning system) this gives very high resolution image, scan rates up to 1million point per sec. advantage High resolution, disadvantage High weight and cost.
Sabre S80 laser scanner (4cm accuracy multiple return laser scanner) lower resolution due to slower repetition rate up to 30,000 points a sec. Advantages low weight low cost, disadvantage lower resolution.
Other lasers like the Velodyne HDL-35E and RIEGL VUX-1 can also be integrated.
After 2 years of development and testing the Sabre Sky3D UAV LiDAR system finalises production model and specifications. Further to this Sabre have developed the HL48 Skyhorse drone which was originally built to deploy the Sky3d system for 30-40 min however is also suited for companies requiring long flight duration high payload capability for many types of sensors. Developed for survey in mind this system can also be utilised for photography, filming and photogrammetry obtaining flight durations up to 60 minutes typically 5 kg for 45min with the main advantage of being a VTOL system
