Abstract
Abstract. The oil and gas offshore industry demands regular inspections of components and structures that are subjected to extreme operational and environmental conditions. In this context, risers are pipelines that transport mainly oil, gas, water, and cables between submarine structures and the surface offshore platform, in the portion not touching the ocean floor. The emerged part of these risers is typically inspected by industrial climbing, which is a very time-consuming activity, has high operational costs, is dangerous and has a strong dependence on inspector skills. Remotely Piloted Aircraft Systems (RPAS) have been recently used for visual inspection of risers, however, no quantitative or geometrical evaluation has been conducted using this kind of image acquisition yet. An image-based measurement technique, such as close-range photogrammetry, can provide a 3D reconstruction using images, but a series of requisites is mandatory to achieve good results as image acquisition sequence, overlap, camera positioning network, spatial resolution and object texture in non-prepared and targetless scenes. The analysis of different image acquisition strategies using a real RPAS is too difficult because it demands a lot of time, good weather, daylight, and a scene similar to where risers are installed. An alternative is to use simulation. In this paper a ROS/Gazebo simulation is described and used to create a realistic textured 3D virtual environment of the platform, risers and RPA, providing a fast and low-cost solution to simulate different RPA trajectories for photogrammetry image acquisition in targetless scenes. These trajectories are evaluated by comparing the measured risers through photogrammetry to its CAD/simulated model. Since the scene is not prepared, the RPA position/orientation or a stereo vision setup can be used to set scale to the measurement result. The best trajectory found during simulations was also evaluated in a real experiment.
Highlights
In recent years, the use of Remotely Piloted Aircraft Systems (RPAS) has been growing quickly across many areas, such as military, security, civil engineering, archaeological, agronomy, forestry, geomatics, and telecommunications (Shakhatreh et al, 2019)
The trajectory performed by the RPA, as well as the use of a gimbal for camera movement, exerts directly influence in geometry intersection, i.e. image acquisition network
PRACTICAL RESULTS Trajectory “C” was performed using M210 RTK v2 (DJI, 2019c) RPA equipped with a DJI X5S camera (DJI, 2019b) and a 45 mm lens
Summary
The use of Remotely Piloted Aircraft Systems (RPAS) has been growing quickly across many areas, such as military, security, civil engineering, archaeological, agronomy, forestry, geomatics, and telecommunications (Shakhatreh et al, 2019). A good acquisition procedure with RPAs can be obtained by a study of trajectories and camera parameters To perform this task using a real RPA is too time-consuming and expensive, requires the use of different hardware combinations such as different camera resolution and focal lengths, battery flight time, weather and requires a location at least similar to riser and platform configuration (Galkin et al, 2019). Simulation tools enable the creation of 3D scenarios with advanced rendering capabilities, flexibility and seamless integration with the robot control system This paper presents the design and implementation of a virtual environment based on ROS (Robot Operating System) (Quigley et al, 2009) and Gazebo (Koenig and Howard, 2004), which enables to quickly evaluate different photogrammetric acquisition strategies, hardware configuration, as camera resolution and focal length, and compare the results using geometric evaluation of the resulting 3D mesh. It was simulated a stereo vision system
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