DRONES: A SURVEYOR’S BEST FRIEND.
Updated: Feb 26, 2021
Drones are everywhere. High priced and low, they are the decade’s new toy. If you have one, you flaunt it. If you don't, you envy those who do. Regardless, there's no doubt that they are also really making their presence felt throughout industrial applications
TODAY Aerial surveys have been a point of contention amongst a lot of surveyors.
Those who are against the new technology, see it as a threat rather than an enabler. The point of the case study was to look into how this new technology could improve the already existing workflows of the surveyor. Our aim was to showcase the value of the technology which will ultimately increase the efficiency of a surveyor on any given project. Yes- we have since learnt that drones are faster and cheaper than traditional methods in some instances, although the South African landscape poses some limitations with the set regulations from SACAA.
With all factors considered, we set to find out how drone technology could improve the already existing workflows of a traditional survey instead of replace them, when calculating stockpiles and building material. The aim was to align man and machine to complement each other towards meeting a common objective.
MAN V.S MACHINE
Traditional Ground Survey
Typically, a GPS is used to determine the position of several hundred to thousands of data points for a stockpile or building material, although there is a margin of error which is approximately 5cm with the traditional GPS method. The process is quite labor intensive and would require the surveyor to be on site for extensive periods of time. A team set to calculate volumes of large quantities of material, can be expensive given the man hours required to carry out the survey. Constant movement of building material and stockpiles also pose a challenge to effectively monitor and manage what is on site.
With aerial surveying, Photogrammetry software can be used to stitch hundreds to thousands of high resolution photographs into complex three- dimensional models. Once the high resolution images are processed, a point cloud is generated that enables calculations, measurements and annotations to be done on that point cloud. Collecting the high definition images requires a fraction of the time on site.
Exploring how man and machine can work hand in hand.
Both the traditional and drone methods were done side by side on a stockpile of material, where a site was being prepared for further earthworks.
Traditional GPS Surveying
The first step in ground-based GPS surveying is collecting GPS point measurements of latitude, longitude and elevation using ground-based survey equipment. The coordinates of the collected points are then uploaded into a three-dimensional space and connected through 3D rays or lines, creating multiple lines emanating from each point. Once the lines have been connected to the neighboring points, they define a surface. Essentially, GPS creates points, points create lines, lines create surfaces and finally surfaces can calculate volumes.
Aerial surveying leverages drones to capture geo-tagged imagery of the area of interest. Once the photos have been gathered from multiple angles, with high degrees of overlap, they are processed in a software package that then uses Photogrammetry to generate a high-resolution orthomosaic map, point cloud and 3D model.
Photogrammetry works by identifying points that are common between overlapping photos and then comparing the geo-tagging data and relationship between overlapping photos to model the points in 3-dimensional space. From there, the software revisits the imagery
Below, are tabulated results noting the comparison between a Traditional GPS survey and a Drone Survey.
Above: An image of the point cloud generated by drone images.
The benefits of drones and their capabilities of conducting surveys are safer, easier and cost effective. This might have been true in this case study, although every new project can pose its own challenges. With the variables considered in this specific case study, the aerial survey came out as the winner. The technology allows for accurate surveys to be conducted at a more rapid speed. Our task was to see how the technology can enable the traditional survey and workflows to be improved.
The surveying company we partnered with on the project, saw the benefits and how drones could enable them to work smarter and faster. Now instead of sending out a large team to single projects, the manager can use his human capital better complemented by drones. Since working with Nafasi, the ground team set out ground control points for improving accuracy of the aerial data. Nafasi will fly the projects, process the data and hand over point cloud data files to the surveying company. The point cloud is then used as a base to do calculations. Now a job that used to take 2 weeks to complete, takes 3 days to complete.
If you would like to incorporate drone services for your surveying projects, we can assist you improve your workflow.