How Drone Topographic Survey Increase The Efficiency of Solar Plant Construction
Written by Falcon Eye Drones and updated 24 February 2019
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In recent years, drones have become an indispensable surveying tool for everyone. Drone survey is the most eﬃcient and fastest method to obtain topographical data. The accuracy can rival the traditional RTK survey technique and the point density that rivals TLS technique is proven. As the distributor and service centre for the senseFly product in the MENA area, we are also owning the largest ﬂeet of drones capable of covering the large area in the shortest amount of time.
Upon completion, the under-construction solar plant one of our most significant projects. During the construction, each zone has its own pace, and various activities such as groundwork preparation, topographic survey, construction, screw and panels installation are happening simultaneously. With the addition of a fully automated ground screw installation methodology, the construction speed increased tremendously.
To increase the time eﬃciency, the solar plant construction project was using fully automated ground screw installation solution. A fully integrated software, cloud and hardware solution that can save the solar installation me by 10-30%. The solution uses computer-aided design to plan the location and the depth of the screw, and then use the fully automated RTK-guided machinery to install the ground screw. The solution requires a highly detailed topographic model to work on, and usually, the ground point density has to be more than 5 per sq meter. Using a traditional surveying technique will be too tedious and ineﬃcient, and still will not be able to provide a suﬃcient point density for generating a detailed topographic model. Terrestrial laser scanning (TLS) can provide such a point density, but it is more time-consuming and less ﬂexible compared to a drone survey. Ground Screws
The Drone Topographic Survey
Once all the initial ground preparation works are completed, the blocks are ready to be 3D constructed. The data was acquired by using SenseFly eBee Plus drone at a GSD of less than 3 cm. In each ﬂight, we can cover 3 – 5 blocks depending on the size and shape of the blocks. Usually, the data could be delivered the next day phase by phase. Depending on the urgency of the data, it is also possible to provide the data on the same day when necessary. With the coordination of diﬀerent construction zones, multiple blocks from diﬀerent zones can be covered in the same day; this ﬂexibility is one of the key advantages of drone.
senseFly eBee ﬂight planning
The accuracy of 1 cm RMSEz
We are following the latest data accuracy standard guideline, develop by American Society of Photogrammetry and Remote Sensing (ASPRS), in which RMSEx and RMSEy deﬁne horizontal accuracy, and RMSEz determine the ver cal accuracy. At the initial stage of the project, we are promising and delivering the elevation accuracy of 6 cm RMSEz. With the improved standard operating procedures, we were able to improve the result to 1 cm RMSEz. The result of one of the ﬂights for block 180 is shown below, where 24 checkpoints are used. RMSE is the statistical veriﬁable measures of accuracy, but how does the actual accuracy look like in the real world?t
Implementation of Drone Data
With the topographic drone model, automated vehicles will start with screw location marking on the ground; this is where the ground elevation will be checked and compared with the drone data. The colours show the diﬀerence between drone topographic data and automated vehicles measured data. As shown in the colour table below, the points from light blue to yellow indicate the accuracy is within 5cm. For block 180, there is a total of 2954 points, 2641 points are within the accuracy of 5 cm, which is a fascinating 89.4%! There are 313 points where the error is more than 5 cm. From the orthomosaic, we know that some of the errors are coming from the trenching activities along the road (North-East of the block). According to the contractor, the errors are also coming from soil movement when the automated vehicles or other vehicles were moving within the area and even the inclination angle of the robotic arm during the marking process. With our improved standard opera ng procedures, we are reaching 83% data accuracy on average for all the blocks.
Total of 2954 ground screw points, the errors are represented by using diﬀerent colours.