In March 1980 the Continental Shelf Institute (IKU) deployed its first buoy with wave direction measurement capability. This buoy was a result of a joint development by the Christian Michelsens Institute in Bergen and IKU. Since then IKU, latterly the Oceanographic Center, has carried out oceanographic and meteorological measurements with several buoys of this type totalling over 10 years of operations at a number of locations from the tropics to the high Arctic. Operating these buoys in remote areas can be very expensive and IKU saw the need for bringing the data collection costs is to increase the maximum operational period for the data buoy and thereby reduce the number of expensive field cruises to a minimum. In order to achieve this without reduction in data recovery it is a requirement that the measurement process be carefully monitored.
The first generation wave direction buoys utilized the Argo satellite system for monitoring the meteorological sensors and some house-keeping functions. However, the wave measurement and recording process could not be monitored well enough to justify a long operational deployment. As a first step to overcome this problem, IKU developed an in situ wave processor in 1981-82. This processor was capable of computing the l-dimensional wave spectrum in addition to some zero-crossing parameters based on the wave elevation time series. A prototype version was installed in a buoy and was tested on Haltenbanken offshore mid-Norway and provided real time wave data for six months. However, the systems still lacked wave direction data in real time. This first prototype was based on a first generation CMOS microprocessor and was quite bulky, the software being written in assembly language. To implement wave direction processing using this system would have required too large an effort. IKU therefore decided to make use of the latest processor technology and high level real time language for the next generation in situ processor. This together with the need for a more flexible data acquisition system and a more lightweight buoy with better dynamic response, lead to the development of a completely new data buoy, WAVESCAN.
In the paper we describe how the final system design evolved from design concepts through a prototype field tests. A historical review is first presented discussing the various design solutions which have been employed for the collection of directional wave data from buoys over the past 25 years. With this in mind the WAVESCAN design aims are discussed. This includes a description of the series of model wave tank tests carried out in order to try and quantify the response and stability characteristics of a number of possible design solutions. Next, the "brain" of the WAVESCAN system - the data acquisition and processing unit - is described. This system includes real-time directional wave processing by standard FFT method. This results may then be transmitted to land by way of the ARGOS satellite data collection system.
Fig. 1 The WAVESCAN prototype (left) and the NORWAVE ODAS 492 buoy at Haltenbanken during the October 1984 field tests.(available in full paper)