UAV Data For Defect Measurement
Inspecting hard to reach assets has always been problematic for a number of reasons including:
Cost and time taken to erect scaffolding, hiring cherry pickers etc.
Safety concerns with working at height and rope access
Disruption caused to asset owner
Consistency of decision making
UAVs have been shown to offer massive advantages over traditional methods by being able to capture high resolution aerial imagery from a variety of angles. The main objective of this is to provide a "high level" survey to highlight problematic areas, so that a survey team is only deployed where necessary.
Studying aerial imagery can only give a limited amount of information about a defect, and often a survey team is then required to go to the defect and take measurements to determine if work is required. So although aerial imagery is extremely beneficial, there is still a substantial cost involved with re-surveying the defect to check if it poses a risk.
Author: James Dunthorne
Published: 12 August 2016
During my time working at Remote Aerial Surveys (RAS) we completed a survey with Severn Trent in order to develop specialist UAV services to enable them to inspect the condition of cracks in the buttresses of a dam. Input from Severn Trent has been invaluable in developing the service, and we look forward to working with them again in the future. High resolution imagery was captured to scope out potential problems on the face of their dams, and then these areas were modelled with higher detail to enable 3D analysis of the defects.
This service allowed asset owners to model their defect in 3D with extremely high levels of detail. Data can be analysed either as a 3D point cloud or as a mesh in a variety of different software programs (including GIS and CAD). Cross sections of the defect can be extracted, and checked against client supplied thresholds using specialist techniques. Below is a short video animation showing a point cloud of one of these defects.
Measurement tolerances have been demonstrated down to a single millimetre, meaning that even small defects can be analysed effectively. All of this information is then compiled into a report which tells the client exactly what defects exist, and the status of those defects. Cross-sections are also provided to allow the client to verify the measurements taken.