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Positioning and System Setup

As opposed to the use of excavators on land, dredger excavations generally do not allow for terrestrial mapping with wooden pegs. Nevertheless, the construction is supposed to be carried out within low tolerances. Automated systems are applied for the control of dredgers, utilizing global positioning systems (GPS). Via offsets and angle transmitters, the dredger geometry and the position of the dredger’s excavator shovel is indicated on a screen together with the required structural geometry.

Hardware: an installation in an excavator generally requires two GPS-systems or one GPS-system with a gyroscopic compass next to a computer, a screen, and a corresponding power supply. The screen is mounted at the front of the driver’s cab to make it well visible to the operator. The computer is generally placed behind the operator’s seat, the GPS-antennas are screwed or welded to the rear of the excavator (left and right). In addition, several sensors for detecting various movements are mounted on the excavator.

Software: the sensors transmit their data to the excavator software (e.g. PCX) for a visual presentation of the excavator shovel. The structural geometry is calculated by means of the CAD-systems, then converted into the format of the respective excavator software, and finally conveyed to the system.

Result: the operator can carry out the required tasks by means of three-dimensional screen images. Each technique has its advantages and disadvantages. GPS-systems are not always able to obtain the needed positioning accuracy. The number of currently available satellites, the satellite geometry, the radio working range and the reception of the reference station, the precision of angle transmitters, the quality of software, and a multitude of other factors influence accuracy and availability. In spite of its limitations, however, the excavator positioning by GPS is often the most economical solution in regards to availability, rationality, and precision.