| ACRONYMS | DEFINITION |
|---|---|
| AGDS | Acoustic Ground Discrimination System: a system that uses data from an echosounder to determine the type of the seabed |
| 3D | Three-dimensional |
| ASCII | A common computer format for human-readable text data |
| Attitude | The angular orientation of the system |
| AUV | Autonomous Underwater Vehicle |
| B2 | Bathyswath-2 |
| B2O | Bathyswath-2 Omega |
| B2S | Bathyswath-2 Standard,also known as B2 Deck Unit |
| B3 | Bathyswath-3 |
| B3A | Bathyswath-3 Alpha |
| B3S | Bathyswath-3 Sigma |
| Bathymetry | Measuring depth |
| Bathyswath-H | High-frequency Bathyswath variant, working at 468kHz |
| Bathyswath-L | Low-frequency Bathyswath variant, working at 117kHz |
| Bathyswath-M | Medium-frequency Bathyswath variant, working at 234kHz |
| Bathyswath-UW | A Bathyswath system with the electronics, motion sensor and sound velocity sensor installed in an underwater bottle. |
| Beam-former | A sonar system that generates discrete beams of angular measurement to the seabed. Synonymous with ‘multibeam’. |
| CAD | Computer-aided design: computer software drawing packages |
| Chart datum | A nationally or internationally agreed baseline for height measurement |
| COTS | Commercial-off-the-shelf: i.e., bought from a shop, rather than specially built for a one-off job |
| CW | Continuous Wave |
| DC | Direct current |
| DGPS | Differential GPS: improves the accuracy of basic GPS by comparing the position obtained by a GPS system with that obtained at a fixed GPS station at a known location |
| DTM | Digital Terrain Model: a digital ‘map’ of the seabed, where depth and sidescan data are stored with reference to their geographical position |
| DU | Deck Unit |
| DVD | Digital versatile disk |
| EMC | Electromagnetic compatibility: robustness to external electrical ‘noise’ signals, and limiting transmission of such unwanted signals |
| Ethernet | A commonly used method for connecting computers together in local networks |
| FGPA | Field-Programmable Gate Array |
| GMT | Greenwich Mean Time; time zone; the Bathyswath software works in GMT |
| GNSS | Global Navigation Satellite System |
| GPS | Global Positioning System: a GNSS, maintained by the USA |
| Grazing angle | The angle that a sound ‘beam’ makes with the seabed |
| Grid file | The file used by the Grid Processor application to store its data. Uses an ‘.sxg’ file extension. |
| Horizontal range | The maximum reach of the sonar, measured horizontally along the seabed; compare with ‘Slant range’ |
| Hydrography | Measurement of physical characteristics of waters; commonly used to refer to those measurements and descriptions of navigable waters necessary for safe navigation of vessels |
| Interferometer | A sonar system that measures depths by comparing the phase of the signal received on a set of vertically separated transducer staves. Also called ‘Phase Differencing Bathymetric System’ (PDBS) |
| Inverter | A unit that provides mains (120 or 240V AC) power supply from a DC supply, usually from a battery |
| IO | Input – output |
| ITS | ITER Systems |
| Line spacing | The distance between survey lines run across the seabed |
| LVC | Line Voltage Conditioner: a unit that ‘cleans’ a power supply, to reduce the effects of ‘noise’ or possibly damaging ‘spikes’ in the supply |
| MRU | Motion Reference Unit |
| Multibeam | See ‘Beam-former’ |
| NMEA 0183 | A standard computer interface for marine equipment, maintained by the US National Marine Electronics Association |
| Noise | Unwanted Signal |
| NTP | Network Time Protocol: a method for synchronising computer clocks over a network |
| OEM | Original Equipment Manufacturer |
| Online help | The electronic user manual that is accessed directly from Swath Processor |
| Patch test | A method used to calibrate the relative locations and angles of the components of a survey system, by comparing depth results from overlapping survey runs |
| PC | Personal Computer |
| PC Clock | Recording the time of a data sample using the time of the computer’s clock at the instant the sample is received in the software. Compare with ‘Sensor Clock’ |
| PDBS | Phase Differencing Bathymetric System; see ‘Interferometer’ |
| Ping | A complete transmit-receive cycle, measuring depth and sidescan information over a profile of the seabed. Also sometimes used to refer to just the transmitted acoustic signal. |
| Post-processing | Processing sonar data after it has been collected; compare with ‘real time’ |
| PPS | A system of electronic pulses for synchronising subsystem clocks |
| PRF | Pulse (or Ping) Repetition Frequency |
| Profile | A 2D set of depth measurements, usually taken sideways from a survey vessel |
| PSU | Power Supply Unit |
| QA | Quality assessment |
| Raw data file | The file used by the Swath Processor application to store raw data. Uses a ‘.sxr’ file extension. |
| Real time | Data processing at the same time as data is collected; compare with ‘Post-processing’ |
| RF | Radio frequency |
| RIB | Rigid inflatable boat |
| ROV | Remotely-operated underwater vehicle |
| RS232 | A commonly used format for serial data connections |
| RTK | Real-time kinematic GPS: an accurate form of GPS measurement |
| Sensor Clock | Recording the time of a data sample using a clock maintained inside the sensor itself. Compare with ‘PC Clock’ |
| Session file | The file used by the Swath Processor application to store its settings. Uses a ‘.sxs’ file extension. |
| Sidescan | Images of the seabed using the amplitude (strength) of the acoustic returns from the seabed. These are usually represented as grey pixels in a ‘waterfall’ display on the screen, with the brightness of pixels representing the strength of the signal. |
| Slant range | The maximum reach of the sonar, measured in a direct line from the sonar transducers to the seabed; compare with ‘Horizontal range’ |
| Spreading loss | Reduction of the amplitude of the sonar signal as it passes through the water |
| Squat | Change in height of a vessel in the water as the vessel moves |
| Survey line | An area of the seabed is usually surveyed by running a series of parallel straight lines across it |
| Swath | The Swath Processor application |
| swath | A ‘ribbon’ of seabed depth measurements, made up of a series of ‘profile’ measurements of depth as the sonar is moved forwards over the seabed |
| SWATHplus | Previous versions of the Bathyswath sonar were called “SWATHplus” |
| swathRT | A real-time data acquisition and control program for Bathyswath, which can be compiled to run on Linux, Windows, and other operating systems |
| Swath-sounding | Measuring the depth in a line extending outwards from the sonar transducer, then moving forwards to build up swaths |
| TCP/IP | A data format used to transfer data over Ethernet. UDP/IP (UDP) is another type. TCP/IP is a more reliable protocol, but is slightly slower. |
| TEM | Transducer Electronics Module |
| Third-party software | Software that is produced by organisations other than Bathyswath or its clients |
| TIU | Transducer Interface Unit: the box containing the TEMs |
| Transducer | The component that is placed in the water and converts sound energy into electrical signals and vice versa |
| TVG | Time-varying gain: an adaptable gain correction applied to sidescan data to remove the gross changes in amplitude caused by range and transducer beam shape, leaving an image of the seabed itself |
| UDP | User Datagram Protocol; see ‘TCP/IP’ |
| UPS | Uninterruptible Power Supply: a power supply that maintains a mains power supply from battery if the mains supply (e.g. from a generator) fails |
| USB | Universal Serial Bus. A common computer peripheral interface. |
| USV | Unmanned Surface Vehicle (radio-controlled or autonomous boat) |
| UTC | Coordinated Universal Time; a time zone, equivalent to GMT |
| UTM | Universal Transverse Mercator: a commonly used format for representing latitude and longitude positions in a plane representation as Easting and Northing |
| UUV | Unmanned Underwater Vehicle: includes AUVs and ROVs |
| V-bracket | The V-shaped mechanical assembly that holds a pair of transducers |
| XTF | An industry-standard data format commonly used for sidescan data. These files use a ‘.xtf’ file extension. |
| xyz | A position in three-dimensional space |
| xyza | Three-dimensional position plus amplitude |
| ZDA | An NMEA 0813 protocol message that is used with PPS signals to synchronise subsystem clocks |