Environmental Engineering Reference
In-Depth Information
Second, weather buoys can serve as the primary on-site data-gathering station for
ocean parameters, including waves, currents, water levels, temperatures, salinity, and
others, relieving the need to measure these parameters on a fixed platform. Last, fol-
lowing the deployment of fixed, primary monitoring stations, one or more weather
buoys can be deployed (or redeployed) throughout the project area to supplement the
wind resource assessment campaign.
The buoy's basic atmospheric monitoring package should include wind speed and
direction (using redundant sensors at least 3 m above the water surface), barometric
pressure, and air and water surface temperature. The buoy should include an onboard
data acquisition system, power supply, and a communication package capable of trans-
mitting data at least as often as every 2 weeks. Including a GPS position reading in
the transmitted data will help the owner track the buoy in the event it comes loose
from its mooring and drifts.
14.2.5 Data Logging and Communications Systems
Data logging and transfer are performed offshore in much the way they are on land:
data are collected and stored temporarily in a data logger, then retrieved remotely, or
if that is not possible, during site visits. Because of the cost and time required to visit
an offshore platform, it is recommended that additional redundancy be provided to
make the data collection and remote transfer as reliable as possible. A second, parallel
data logging system should be considered as a backup. It is also recommended that a
computer, or other redundant data storage device, be placed on-site to provide backup
storage in case of an extended communications failure. If a computer is used, it should
connect the different monitoring systems in one network. If equipped with redundant,
high capacity data storage (e.g., a disk array), the computer can serve as a reliable
repository for data from all the networked devices. In addition, if properly equipped,
the computer could provide a redundant means for remote users to interface with
the devices.
Highly reliable communications are needed to transmit and receive the data and
monitor the status of equipment deployed offshore. Accordingly, a redundant remote
communication and control system is recommended for all offshore monitoring equip-
ment. The communications system must also have sufficient bandwidth, or speed, to
support the required volume of data to be transferred. Given that many offshore
project sites are located outside the coverage areas of cellular networks, cellular com-
munications may not be feasible. A satellite connection is a possibility, but it may
not be adequate for transferring large data files because of bandwidth constraints,
data-transfer caps, and cost.
Often, a point-to-point radio connection is the best option for transferring large
data files and providing rapid (low latency) remote access to offshore systems. This
technique, which is rarely employed for land-based resource assessment, uses a pair
of directional antennas pointed directly at one another to connect a base station com-
puter on land to a remote computer on the offshore platform (Fig. 14-11). Operating
on licensed and unlicensed RF bands, the antennas form a high bandwidth wireless
network connection between the two computers. Files can be transferred from the
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