Far North and Out of Sight: Corridor Mapping of Powerlines in Iceland
The project was to map and survey powerlines for Landsnet (co-presenter), the main transmission system operator in Iceland. The first zone Delair had to map was North in Akureyri where Landsnet would like to build a new powerline between Akureyri and Holasand. The main goal was to improve energy efficiency by increasing the transmission capacity and ensuring the stability of the power system. In order to make these assessments, Landsnet needed to have precise measurements of factors such as sag, span, distance between individual lines, and whether or not the pylons had subsided in the constantly rising and falling surface of the tundra landscape. In this particular part of Iceland, many segments of the proposed corridor are difficult to reach due to terrain and rivers. The use of a UAV solution allowed rapid and efficient mapping of 70 km of corridor in remote areas. Delair collaborated with EFLA Consulting Engineers (co-presenter) to conduct the first UAV LiDAR flight in Iceland. A Delair DT26X UAV equipped with a Riegl VUX-1 LiDAR sensor and an Applanix APX-15 UAV GNSS/IMU were used for data collection, producing 75 points per square meter with a one sigma accuracy of less than 4 cm horizontal and 2 cm vertical. In addition, a Delair DT18 HD PPK with a fully-integrated RGB camera sensor enabled EFLA and Landsnet to get a clear view of the area of interest for the construction of the future powerline. In some areas both LiDAR and photogrammetry data were acquired over existing powerlines in order to compare results between the two methods. The LiDAR data indeed provided more accuracy in the Z axis and enabled the creation of highly-accurate models of the conductors, insulators, and towers. This made it possible to easily vectorize the assets in three dimensions. Dedicated algorithms were run on the dataset for semi-automatic classification of the point cloud and to take measurements including ground clearance and distance between different lines. The photogrammetry process generated a precise digital surface model (DSM) that gave EFLA insight as to the topography along the corridor proposed for the new lines. Taking advantage of the extended flight times and communication range of the selected UAVs and being authorized to operate beyond visual line of sight (BVLOS), only 10 flights with the DT18 HD PPK and two flights with the DT26X LiDAR were conducted. The Above Ground Level (AGL) altitude of the UAV was optimized between 150m to 400m AGL to ensure a constant Ground Sample Distance (GSD) by following the relief of the steep and dissected terrain. Only 23 ground control points (GCP) were placed along the 70 km corridor and PPK GNSS data processing ensured the accuracy standards for the project were met. This project faced many operational and data analysis challenges including poor weather conditions, limited daylight at high latitudes, difficult terrain, limited access to a remote area of interest, and short timelines for data delivery. Despite the challenges, this was a successful project that served the purposes of the asset owner in a real-world application.