How Drone Topographic Survey Increase The Efficiency of Solar Plant Construction

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.