Definitions

Acoustic Dopler Current Profiler is used to measure the current flowing below the vessel. It profiles the velocity and direction of water flow from the surface to a depth of approximately 400m (depending on the frequency of the ADCP).

ARPA

Automatic Radar Plotting Aid is an advancement to the standard shipboard Radar display. It can automatically acquire and track many targets, providing accurate and timely information to the watch officer, thereby lessening his workload. This allows the ship to be operated more safely in heavy trafficed areas.

CTD

A Conductivity, Temperature, and Depth sensor is an instrument which is deployed from a vessel todetect and record properties of seawater as it is lowered and raised through the water column. The principle measurements are conductivity, temperature, and pressure. From these measurements depth and salinity can be derived.

Sample Data (11 k)

DGPS

The Differential Global Positioning System is an enhancement to the basic GPS system. This system provides navigational accuracy of 10 meters or less. The system consists of a reference station at a known, surveyed, position. The reference station compares the know position to the calulated GPS position, and developes corrections. The reference station broadcasts these corrections on a radio transmitter, using a standard format. DGPS receivers then receive the corrections and apply them to their calculated GPS position to obtain a very accurate position.

ECS

The Electronic Chart System is a system which electronically integrates accurate chart data with GPS derived ship location, on a PC-based platform. This provides a highly accurate marine navigation system. This system provides the mariner with the ability to navigate to an accuracy greater than was available to the surveyor who collected the chart data. Even the prudent mariner may be tempted to pass a hazard more closely than before, not realizing that the hazard's depected position may be more uncertain than the ship's.

HDAPS

The Hydrographic Data Acquisition and Processing System is used by NOAA's surveying ships and craft to acquire and process hydrographic survey data.

GPS

The Global Positioning System is a radio navigation system which provides precise, worldwide, three dimensional navigation capabilities. The system was designed for military application, however a degraded system is available using a variety of commercial receivcers. The commercial system provides an accuracy of 100 meters, or less, depending on the amount of error added by the military.

LORAN-C

LOng RAnge Navigation - Until the recent introduction of GPS, LORAN-C was the navigational system of choice for coastal navigation on the waters of the U.S. It is an electronic aid to navigation consisting of shore-based radio transmitters maintained by the USCG. A LORAN-C chain consists of three to five synchronized transmitting stations separated by several hundred miles. Position is determined by measuring the time difference in the arrival of the signals from various stations.

MOCNESS

The Multiple Opening and Closing Net and Environmental Sensory System is a towed system which has several nets on a single frame which can be sequentially opened and closed by researchers on deck, with real time readout of the water characteristics that the net is in. This allows sampling of a specific zone, such as only above or below a thermocline or other mass delimiting boundary.

MOCNESS Deloyment (61 k)

NITROX

NITROX is an enriched air nitrogen-oxygen mixture commonly used in diving. It contains 68 percent nitrogen and 32 percent oxygen. The lower nitrogen concentration reduces the need for decompression stops and may also reduce the narcosis problems. The use of NITROX makes longer dives safer than the those using standard compressed air.

ROV

A Remotely Operated Vehicle is an underwater instrument deployed from a vessel with the ability to maneuver independantly from the vessel. Through the use of video cameras and other sensors, it can collect images and data which would otherwise require divers.

ROV Piloting (32 k)

SAFE

A Secure Around Flotation Equipped boat is aluminum hulled with a solid, closed cell, polyethylene foam collar. This construction makes the boat a very good heavy weather platform.

SEAS

The Shipboard Environmental (Data) Acquisition System is a global volunteer observing ship program operated by NOAA for the collection of marine meteorological and ocean data. Observed weather data is entered into the SEAS program running on a PC. This data is transmitted to NOAA using an Inmarsat C Transceiver. Most of NOAA's research ships participate in this program. See the SEAS page for further information and links to current SEAS data.

XBT

An Expendable Bathythermograph probe consists of a small projectile with a leaded nose and a plastic casing that contains a spool of fine copper wire. As the probe descends through the water column, the wire self-spools and transmits the temperature from a thermistor in the nose to a recorder on deck. Corresponding depths are computed from an empirically-derived, second order fall rate equation given by the manufacturer of the probe.