The cost of a rubble-mound breakwater, its expected behaviour, as well as the consequences of its failure, do justify the existence of a monitoring programme which helps in the decision making process relative to the timing of the maintenance, or even repair, works. However, the continuous monitoring of the status of any given breakwater stretch is not yet feasible. That is why the most common procedure consists of the periodic inspection of these structures. The goals of the MEDIRES project are two fold:
i) To use the latest technological breakthroughs in positioning, navigation, and control of surface autonomous vehicles to develop new techniques for accurate and efficient inspection of the geometry of semi-submerged structures with application to rubble mound breakwaters. This activity will end up with the development of a tool, named IRIS, for high accuracy surveying of both the above water and submerged parts of the armour layer of rubble-mound breakwaters (or semi-submerged structures, in general). This tool that can be used in autonomous mode or equip an Autonomous Surface Craft to produce tri–dimensional surveys with the spatial regularity required for this kind of structures;
ii) To condense the large volume of data from the periodic inspections into a small set of parameters that enables the characterization of the structure’s status and evolution. The definition of the parameters thresholds, needed for the structure’s diagnosis, will be based on LNEC’s past experience as well as on results from scale model tests.

The tool (IRIS) will be designed to equip the autonomous catamaran DELFIM, property of IST/ISR. Within the framework of this project, accurate path following control and navigation systems will be developed in order to guarantee the repeatability of the maneuvers so as to ensure the quality of the survey data sets obtained. Nevertheless, the IRIS can be used in a standalone mode without the autonomous vehicle.
The autonomous catamaran, named DELFIM, is capable of following pre-assigned trajectories with a high level of accuracy. It is equipped with two back electrical thrusters and can travel at a maximum speed of 5 knots. In order to determine its position and speed it uses differential GPS and an attitude reference unit. Using the information available from its motion sensor suite the catamaran DELFIM computes its actual position and orientation and respective velocities.
A real time computer network developed at the Institute for Systems and Robotics is used in the autonomous vehicle DELFIM. This network was specially designed for multi-vehicle robotic applications, uses wireless modems, and implements TDMA (Time Division Multiple Access). The network will effectively allow an operator to supervise the IRIS tool during the survey.
The inspection techniques to be developed within the framework of this project will be tested in Sines’ West breakwater and in the breakwater of the Aviles port (in Asturias, Spain). Several surveys will be conducted during the project, to identify and tune the algorithms and tools for online data set acquisition and off-line processing.