Chapter 4
Using the system
4.1 Calculated parameters
Once the system is commissioned the facilities of data presentation, reflection diagram,
system info etc. can be used to monitor the proper operation of the system.
Water level and wave height information are calculated by analyzing the measurements of
the WaveGuide radar. There are two analysis routines:
Wave analysis
The Standard Wave Processing Package (SWAP) is used in performing time and frequency
domain analysis on the measured data to calculate wave p arameters. This package is the
standard processing package used by the Dutch government for wave height analysis. It
also meets the standards set by The International Association of Oil & Gas Producers
(OGP). A detailed description of the SWAP package is available on the Radac website
(
http://www.radac.nl).
The SWAP parameters are calculated e very minute using 20 minute data blocks. The 20
minute observation block is chosen as a compromise between short enough to obtain "small"
variance in the statistical parameters and long enough to assume it to be a stationary
process. The time stamp used on SWAP parameters is the mean between the start and end
time of the 20 minute data blocks.
Waterline level analysis
To analyze the ship’s waterline level a number of long term averages are available. The
parameters H10, H5 and H1 are calculated by averaging uncompensated measured water
levels (heaveRadar) over 10 [min], 5 [min] and 1 [min] periods respectively. By origin these
parameters are used to indicate the waterlevel from a static ob ject.
Each parameter receives a time stamp central to the block of data that was used for its
calculation. The spectra and parameters that can be calculated by the WaveGuide system
are described in Appendix 1. Due to the large number of parameters, only a selection of the
most commonly used ones is displayed on the user interface. This selection can be modifi ed
by Radac upon request.
4.2 Data logging
Each WaveGuide Onboard system is supplied with internal non-volatile memory (an SD
card) for data logging. This can be used as a backup solution while sending data over
the network to a primary data acquisition system. To reduce the chance of corrupting the
SD-card during power failure, it is advised to use an Uninterrupted Power Supply (UPS).
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