In October 2015 Orbiton – in collaboration with the engineering firm Dr.Ing. Aas-Jakobsen -was awarded Norway’s first ever comprehensive RPAS tender, for bridge inspections for the National Public Road Authority (NPRA).
The contract encompasses the inspection of about 300 bridges on a yearly basis in Oslo, Akershus and Østfold in the period 2015-2020. Bridges that are difficult to access will mainly be inspected with drones.
This is the first time the NPRA focuses on systematic use of drones for the inspection of their infrastructure and the project represents a groundbreaking and pioneering initiative in Norway.
A SMOOTH AND EFFICIENT SOLUTION
The first inspection was completed on Monday October 12th at Langset bridge at Minnesund in Akershus. Shortly thereafter, 6 other bridges on the E16 and E18 were inspected. The bridges have previously been visually inspected from ground level using ladders, snooper trucks, scaffolding, boats or climbers. In most cases, traffic must be stopped or re-routed, and operations often take place at night.
Using drones, the inspections could be carried out in daylight without closing the road and without the comprehensive and costly procedures that come with nighttime operations. Inspections were mainly conducted without the need for warning signs, albeit after a thorough SJA and approval by roadwork safety personnel. Because of its size, the drone is so difficult to spot by motorists that it does not affect normal traffic flow.
During the inspections, several types of sensors and lenses were tested. The choice finally fell on a 24 Mpix sensor with a fixed 50mm lens. Stills were also chosen over video. In this way, data with a high degree of detail were assured.
Bridge inspections with drones place high demands on personnel and equipment due to many potential hazards. Flights were carried out alongside roads with heavy traffic, in urban areas and along railway tracks and overhead power lines. This required a thorough initial risk analysis. The pilot and sensor operator had to handle various – and simultaneous – obstacles. Difficult lighting conditions require extensive photographic knowledge as well as technical understanding of the sensors in use. The drones are exposed to varying atmospheric conditions, and electromagnetic radiation is also a particular hazard that must be strictly observed.