Online data collection can be implemented in a variety of ways but they all share two fundamental characteristics:
- The data must be transferred to shore and then onward to the user site
- Power must be supplied to the instrument
A power and communication cable from shore to the instrument can achieve both objectives (see figure 1). For this reason, this method is the most straightforward solution. However, power and communication cables are subject to failure in harsh environments so this is not the only solution. Nortek has spent a significant effort to ensure that the cabled systems are both functional and reliable. This includes a good quality cable that is abrasion resistant, an interface unit on shore, and software that can receive the data. The practical elements required for cabled systems are described here.
In order to separate power and communication, the instrument must be deployed with enough batteries to both power the instrument and the communication system. The advantage is that a power cable is no longer required, which opens up the possibility of using acoustic or inductive modems to transfer the data to shore. Acoustic modems are good alternatives in situations where cables cannot be used (see example in figure 2), such as communication to surface buoys. However, acoustic communication can only be used over fairly short distances and where
there is line of sight between the acoustic modems. More about acoustic modems here.
An alternative to acoustic modems is inductive modems, which only require a low-cost single wire jacketed cable to transfer data from the instrument to shore. The cable used for inductive modems is more rugged than an online communication cable and can even be used as a mooring cable for small surface buoys. It can also be used to transport data over longer distance than an acoustic modem. Nortek has tested inductive modems from Seabird (to be used with Nortek Aquadopp) and from RBR.
Software solutions for online systems.
A variety of software solutions are available for your online system.
a) PC-based data collection.
The Nortek SeaState software can be used to collect data from AWACs, Aquadopp profilers, or Continentals that are connected to a PC. The software will receive the data in real time, display the data on the screen and store the data on a storage device or transfer subsets of data or images to other computer in the network. This is the traditional solution for local data collection and it works well when data are primarily collected for local use.
b) User supplied software solutions
The Nortek Paradopp interface manual describes in detail the communication protocol, the interfacing commands, and the data formats of the various Nortek instruments. With this information it is possible for the user to write proprietary software that handles the data collection and communication control across the chain of communication devices used in the transport of data from the instrument to the user site. These systems can become quite complex as the number of systems increase and Nortek supports this user-initiated activity by supplying a variety of data formats and online commands that make the integration doable in most programming environments.
The AOS system was developed for
- Deployment in areas with no power supply
- Organizations that do not have the internal resources to develop their own software system
The AOS is an advanced hardware and software solution for online systems that includes data transfer to the Internet over iridium satellite, a GPS locator, a server to store the data, display software that shows the data on the WEB, and export functions to the user computer to allow further data analyses.