Station Configuration

CBI-DNR uses several different data collection systems to obtain environmental measurements. Each station has sensors for measuring the various environmental parameters, a data collection computer for controlling the sensors and temporarily storing data on-site, one or more telemetry devices for retrieving data from the station, and solar panels and batteries for power. The instrument configuration at each station is dependent on the purpose of the station and the local conditions. For example, the instruments used to measure parameters such as water current, salinity, and dissolved oxygen are expensive to install and maintain, thus they are only deployed at a limited number of sites. The presence of buildings or other physical structures near a data collection station may prevent accurate wind measurements; as a consequence, wind is not measured at such stations.

Most TCOON stations use a Next Generation Water Level Measurement System (NGWLMS) as designed by NOS . At the heart of the NGWLMS system is a Sutron 9000 computer that controls the attached sensors, collects and stores environmental observations, and transmits the observations via satellite, radio, or telephone modem. The Sutron 9000 has been quite reliable for TCOON operations; however these systems are beginning to deteriorate with age and it is difficult to find repair or replacement parts. As a result, in the past several years CBI has gradually migrated to using Vitel VX1100 Data Acquisition and Telemetry Unit computers for data collection at some stations. The VX1100 system provides much of the same functionality and capability as the Sutron 9000 at a lower cost.

For other projects such as the Corpus Christi Real-Time Navigation System and the Freeport FlowInfo System, CBI-DNR has developed a data collection computer using industry-standard PC-104 computer components. A typical PC-104-based data collection computer consists of an Intel 486 or Pentium processor, 16 megabytes of RAM, and at least 20 megabytes of solid-state hard disk space. The data collection computer runs a modified form of the Linux operating system; this allows the use of a rich set of software development tools and provides a robust multitasking environment for controlling sensors, storing data, and doing on-site processing such as data compression for transmission over bandwidth-limited communications channels.

The sensors used to measure environmental parameters include acoustic transducers for measuring water elevations, wind anemometers for wind speed and direction, acoustic doppler current profiling instruments, multiparameter water-quality probes, and other similar instruments. Each of the sensors is interfaced to the data collection computer via serial communications ports or analog-to-digital conversion hardware. CBI-DNR has an operations staff that performs routine maintenance and calibration of each sensor.

All the stations in TCOON and related projects measure environmental parameters at some multiple of six-minute intervals. For example, water-level measurements are taken every six minutes, while other measurements such as salinity or barometric pressure may be made every thirty or sixty minutes. The data are stored on-site in the data collection computer and then transmitted to CBI-DNR by one or more communications channels including satellite, spread-spectrum packet radio, or telephone modem. The choice of communication medium used for a station depends on the availability of telephone or radio connections and the degree of need for real-time observations. For example, stations in the Corpus Christi Real-Time Navigation System and Freeport FlowInfo System use line-of-sight packet radios to allow for frequent acquisition of data from the on-site data collection computers-typically downloading new data once every twelve minutes. At stations where radio or telephone connections are not available, satellite transmissions are used to transmit data at hourly or three-hourly intervals. Thus, the time from measurement to acquisition at CBI depends on the measurement interval and the communications medium used. The data arrive at CBI somewhere between six minutes and six hours after measurement.