Monitoring the site "Langes Feld"
Long-term monitoring of a constrction site in Kassel
Kassel, one of Germanys most dynamic and growing cities is facing several large construction sites to get ahead of the demanding tasks. Especially the growing need for residential property and industrial estate in and around the cities shapes every planning process, the municipality faces. With an approximated construction volume of over 70 million euro and an area covering 136 hectares, the exploitation of the business park “Langes Feld” ranks high in the biggest construction projects in the area. Planning to sell the first areas close to the motorway A49 due 2017, efficient time management was needed. Using the industrial drone Aibot X6 to get a clear view on the sites progress helped to stay on schedule.
Precision from the beginning
To coordinate 40 construction worker and 18 earth-moving machines on site, perfect planning and a steady stream of information is necessary to get a clear view over current tasks. A typical task of surveyors to support the construction management is the providing of precise geo-data and scrutiny of moved masses. Using the collected data, economic and environmental alternatives can be shown to decision makers to increase sustainability and efficiency.
High resolution digital cameras attached to unmanned aerial vehicles (UAV) is becoming more and more a credible alternative in surveying and mapping to traditional terrestrial methods. Using photogrammetry, for many a formerly unloved field of education, allows you to take up large areas of interest within a very short span, so it is getting more into the focus of engineers. Even if you look at the accuracy-level drones do not have to hide behind the common GNSS technology. Highly detailed point clouds, orthophotos and DEMs (digital elevation models) are possible results that can be created with the industrial drone Aibot X6. With additional software solutions there is even the possibility to create high precise stereophonic pictures.
In addition to the traditional ways of surveying the construction site, an airborne long-term monitoring was done with the Aibot X6 drone. With the aim to support the conventional surveying services in geo data collection, particularly to control and document the moved masses, qualitative and quantitative proofing and inventory control were the main tasks done with the multicopter Aibot X6. Highest accuracy, fast availability of the collected and increased safety data go hand in hand with reducing costs and surveying a site without any interruption of the ongoing workflows. Additional challenges were vegetation, machinery and working materials in the receiving area. These are also recorded by the drones sensor technology and must be edited during the evaluation.
Autonomous flights under steady supervision
The Aibotix AiProFlight software was used to perform flight planning before the first flight, since comparable data were generated and the flight plan did not change over the period. The user is supported by the use of map material and camera-databases in the for best photogrammetric flight planning. The requirements on accuracy and cost as well as the required repetitive recording of the construction field required an optimal use of the available technology and compliance with standardized workflows. Before any flight was done, ground control points (GCP) had to be measured in to precisely adjust the collected data. The use of the Aibot HP GNSS 2, a RTK-capable GNSS receiver on the Aibot X6 UAV for high-precision direct georeferencing of image data, for the project "Langes Feld Kassel" meant a reduction of expense to a minimum and a clear time saving. In the present case, only one GCP was used to eliminate possible residual errors in the camera calibration. The detailed preparation and the standardized workflows with the Aibot X6 ensured a small time effort for the actual flights. With only two flights, a partial area of the total construction project of 15 ha could be surveyed in a very short time. The high-resolution photos with a centimeter-accurate georeferencing were fed into Agisoft PhotoScan for evaluation. Within only three hours after the flight, the customers were able to get the results of the flights in the form of a georeferenced point cloud as well as an orthophoto for further evaluation. The point clouds were further processed with Leica Infinity software after the first analysis of the data quality.
Reducing costs by increasing value of the information
By using the Aibot X6 drone, it was possible to carry out a complete and accurate condition survey of the construction project every week without entering the site and to move around in the potential danger area and disturbing the ongoing processes.
In addition to a complete and three-dimensional documentation of the construction process, the point clouds with 100 points per square meter were also used to document mass movements and to perform an accuracy check of the earthworks carried out by heavy machines. Disturbing vegetation as well as machines and material can be manually removed from the calculation within a short time. High-resolution orthophotos with a resolution up to 1 cm per pixel were used for areas, lengths and batch determinations and represent an excellent overview.
The repetitive recording at the site "Langes Feld" will take place until the end of construction. With over 50 planned recordings or with the drone, more than 10,000 individual photos are recorded and processed. These data alone will require a TB data store.
Supporting the officials with the collected data, the smooth processing and the speed of available data, the drone prove itself as a valuable and important technique to survey the site during every construction phase.