Business Geomatics online posted an article reviewing how Pirker + Pfeiffer, a German engineering company, enlisted the services of Geoplana, a Microdrones distributor, to carry out as-built surveys and height recordings for a construction project using drone surveying hardware and software solutions from Microdrones.
Drone Surveying in Construction
Construction sites are a complex area to begin with where every cog in the wheel has to turn in perfect synchronization so that everything works according to plan. Inaccuracies in planning or improper execution can lead to catastrophe. Therefore, precision is the key to success on construction sites. But what measures can be taken to ensure the proper requirements are being followed during the construction process? How can progress be monitored while simultaneously making sure all steps have been carried out according to plan or whether all measurements have been accurate?
These questions are the focus of Pirker + Pfeiffer Engineering from Münsingen, Germany, as part of their construction projects. The company has hired Geoplana for photogrammetry, drone mapping and surveying for an as-built survey and height verification of the Rucken construction project with a required height accuracy of 2 to 3 centimeters. In the project on the Feldstetten district, they used the mdMAPPER1000DG from Microdrones, which is equipped with a Sony RX1R II camera and an Applanix APX-15 UAV DG inertial system. The software solutions Agisoft Metashape Professional 1.7.6 and DAT/EM SummitEvolution 7 were also used to create a digital terrain model (DTM), a topographical site plan and true orthophotos. The drone flight was planned using the Microdrones flight planning software mdcockpit.
The area to be surveyed consists of a flat, even terrain with a few buildings on the western edge of the survey. The survey team needed to wait about half a year to conduct the aerial survey, once the fall harvest was complete. Therefore, it was at the end of October 2021, where Pirker + Pfeiffer and Geoplana met on site to review the project.
Before the start of the flight, the client laid out nine signal boards (40×40 centimeters) as pass points, three more as control points and then measured them terrestrially with a tachymeter and levelling. In addition, the 3D coordinates of the signal boards were determined as a basis for aerial triangulation and post-modeling. In addition, as part of the flight preparations, Geoplana applied for a take-off permit from the regional council in Stuttgart and a geographical permit from the airport, which was only 1.5 kilometers away.
Due to the peripheral development, the flight area was planned with two different overlaps in the mdcockpit software from Microdrones. The eastern part was planned with a longitudinal and transverse overlap of 80/40, while the western half overlap was 80/60. The higher overlap enables the creation of high-quality true orthophotos and thus better visibility of the areas between the houses that have already been built. Overall, Geoplana completed the flight in just under 40 minutes in 13 strips with 921 images from a height of 65 meters. The ground resolution was 8.4 millimeters. Due to the size of the area and the relatively long flight time, Geoplana planned a stopover to change the battery of the mdMapper1000DG.
Processing the Data
After Geoplana had carried out the flight and checked the data for accuracy on site, they combined the images into an orthophoto using processing software. The rear projection error was 0.7 pixels. In order to determine the external orientation, the control points in the images were also measured. The orientation of the camera data was also exported from DAT/EM for later evaluation with SummitEvolution.
Based on the inner and outer orientation, Geoplana was now able to create a point cloud for the project area. This is the basis for the required digital surface model (DSM), which in turn serves as the basis for the creation of true orthophotos. After filtering and classification, other applications can also be created from the point cloud such as a DTM.
Drone mapping and measurement flights are becoming more and more attractive for the construction industry. This is due to improved battery life and range of the drones, high-precision camera systems and ever more powerful software solutions for image processing and evaluation. Geoplana took this trend into account in 2020 and therefore founded its own business unit for drones with GEOdrones. GEOdrones not only acts as a system dealer and partner of Microdrones, but also offers users a comprehensive range of services related to drones (drone software, accessories, training courses and photogrammetric evaluations of drone images). The range also includes data processing for customers who can also carry out drone flights themselves.
If you would like to learn more about using drone using drone surveying equipment on your construction projects, talk to one of our knowledgeable sales representatives today.