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Fishfinder, Sonar and GPS Glossary
Humminbird Terminology Guide - Fishfinders, Sonar, GPS
Freeze Frame | Freeze Frame is a Humminbird feature that pauses the sonar scrolling so the image on screen can be studied with greater detail. See also: Instant Image Update. |
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Grayscale | Grayscale is the use of varying shades of gray to represent the strength of the sonar signal on the display. Traditionally, the strongest sonar signals are represented in black, and progressively weaker signals are represented in progressively lighter shades of gray - a very intuitive method of presenting information. Grayscale levels vary by product and price from 4 to 16 levels. With current monochrome display technology it is often impossible to distinguish the difference between higher numbers of grayscale levels such as 12 or 16. Regular grayscale is selected in the Bottom View menu by selecting the Structure ID setting. |
Grayscale, Inverse | Inverse Grayscale is Humminbird feature that reverses the correlation of sonar signal strength and the shade of gray typically used to represent it. The strongest sonar signals are represented by “white”, and progressively weaker signals are represented in progressively darker shades of gray. While somewhat counter-intuitive, this method makes the sonar images crisper, and has the benefit of enhancing the apparent sensitivity because the weaker signals appear bolder. Inverse grayscale works well in very clear water. Debris laden water often appear as much clutter on the screen. Inverse Grayscale is selected in the Bottom View menu. |
Instant Image Update | Instant Image Update is a Humminbird feature that updates all the sonar information on the display when Sensitivity and a variety of sonar settings (Bottom View, Range, etc) are modified. This differs from the traditional functionality that only updates the new sonar information collected after the setting change. Instant Image Update permits more accurate fine tuning of the display because the user can see the results to the complete sonar graph. When combined with the Freeze Frame feature, the user can adjust and understand the effects of many different sonar settings quickly and easily. |
Large Digits Views | Large Digits Views is a Humminbird feature that displays the sonar graph and enlarged digital readouts for easy reading from a distance. This is a great tool when monitoring the digital depth is important – such as higher boat speeds, or when viewing the unit from a distance. When speed input is available, the Large Digits View also shows the Triplog. See also: Triplog. |
Noise | Noise is unintentional external sound waves that interfere with the optimal operation of sonar. Noise appears as random “dots” on the display, and is caused by a variety of sources. Electrical noise (from trolling motors, bilge pumps, VHF radios) typically has a consistent pattern to the dots. Electrical generated noise can be isolated by selectively turning on and off other electrical devices to determine the source. Often rerouting the power cable, or connecting to an alternative power supply (second battery) can help overcome electrical noise. Hydrodynamic noise (from prop and/or hull cavitation) has a more random appearance and is generally related to boat speed – faster operation results in more noise. Hydrodynamic noise can be overcome by proper transducer installation. Many Humminbird products have a Noise Filter menu setting that clears the screen of noise that is difficult to eliminate. |
Maximum Depth Menu | The Maximum Depth Menu is a Humminbird feature that optimizes performance based on the maximum operational depth set by the user. Many Humminbird units can operate across a very broad depth range (up to 2500 feet) which causes the unit to “look” up to that full depth under some circumstances. Due to the speed of sound in water, this can result in less responsiveness because the unit has to wait for a longer period of time to receive the sonar signal. When the Maximum Depth menu is set to a lower value, the unit only looks up to the setting, which increases the responsiveness of the unit. This is an important feature for anyone operating in shallower depths! |
Ping Speed | See Update Rate |
Terminology Guide - Sonar |
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Alarm, Depth | Depth Alarm is a user controllable audible alert that sounds when depth is less than or equal to the setting. |
Alarm, Temperature | Temperature Alarm is a user controllable audible alert that sounds when the water surface temperature equals the setting. |
Backlight | Backlight is a user controllable illumination for the LCD for night and low light use. A typical backlight utilizes incandescent lighting. LED Backlight technology utilizes Light Emitting Diodes which provide a whiter light, and draw less current than traditional incandescent backlights. CCFL Backlight technology that utilizes Cold Cathode Florescent Light which provides very white, very bright light typically needed for sunlight viewable color displays. |
Beam (Sonar Beam) | A sonar beam is the cone shaped projection of sound waves as they travel into the water. See Cone Angle. |
Bottom Black | Bottom Black is a Humminbird feature that “fills in” the area of the display below the bottom contour. Bottom Black is preferred by some anglers because of the high contrast and easy readability, however it obscures bottom hardness information. |
Bottom Contour | Bottom Contour is the profile of the bottom graphed to the screen as the depth changes. |
Bottom Hardness | Bottom Hardness is the density (or composition) of the bottom which can often be determined by interpreting the main sonar return. Varying levels of hardness can be determined by interpreting the “thickness” of the sonar return. Hard returns appear thin and black, softer returns appear thicker and less black. Its important to note that a sonar return from a sloping bottom can have the appearance of a softer bottom. |
Cavitation | Cavitation is air bubbles caused as the prop rotates and the boat moves through water. Hulls with protrusions such as rivets generate more cavitation than smooth hulls such as fiberglass. Cavitation interferes with, and can cause loss of sonar returns from the bottom, fish and structure. See Noise. |
Chart Speed | Chart Speed is a user controllable feature that sets the “speed” at which sonar information moves across the display. A faster setting displays sonar information from more pings and shows more detail, but the information moves quickly across the display; a slower setting permits viewing of more sonar history, but does not display as much detail. The best setting is often the user’s personal choice. |
Cone Angle | The Cone Angle is the angular measurement of the sonar beam at a specific DB down point (i.e. 10db). See also: DB Down Point |
Customizable Digital Readouts | Customizable Digital Readouts is a Humminbird feature that permits the user to select the specific digital information that appears in the main sonar view. (i.e. Speed, Temperature, Barometric Pressure, Triplog, etc). |
Dead Zone | Dead Zone is the area of the sonar beam that receives sonar signal after the main bottom return. Due to this, fish and other objects close to the bottom that fall within the Dead Zone are likely not visible in sonar. Precision sonar beams such as Humminbird 20° beam have a smaller dead zone than wider sonar beams. |
Decibel | A Decibel is the measurement system for sound pressure level, or “intensity” of the sonar return. See DB Down Point. |
DB Down Point | The DB Down point is the standard decibel level at which the sonar cone angle is measured, and written as “@ -10db” or “@-3db”. Measurements at smaller down points (bigger negative numbers) indicate that the less intensive sonar signals are being used for the measurement. Humminbird utilizes the -10db down point as a standard because it more accurately represents the true useable cone of the sonar beam, and the Humminbird receiver can effectively operate at these low signal levels. Some promote the -3db down point as an industry standard (untrue) as it represents the point at which only 50% of the sonar signal will be returned under optimal conditions. The -10 db down point represents the point at which xx% of the sonar signal will returned. The most advanced developers of sonar technology such as the US Navy utilize a variety of DB down points (-3 db, -6 db and -10 db) depending on the application. |
Display, FSTN | FSTN is an acronym for Film Super-Twist Nematic. FSTN is a monochrome display technology characterized by black, high contrast pixels. All monochrome fixed mount Humminbird products use FSTN technology. |
Display, TFT | TFT is an acronym for Thin Film Transistor. TFT display technology the premium color display technology characterized by excellent color representation across the broad spectrum, and fast response time without blurring of images. TFT technology is widely used in PC laptops, and is the technology used in Humminbird color products. |
Display, STN | STN is an acronym for Super-Twist Nematic. STN is a monochrome display technology characterized by bluish pixels. STN technology is used in the SmartCast wrist mount and pole mount displays. |
Dual Beam | Dual Beam refers to the use of two sonar beams simultaneously. |
DualBeam PLUS | DualBeam PLUS is a Humminbird sonar configuration that utilizes two sonar beams simultaneously, and combines the information from both beams into one view by overlapping the data on-screen, or shows each beam individually side by side, or permits each beam to be viewed individually full screen. |
Fish Arch | A Fish Arch is the apparent “arch” that appears on the display when any object moves through the sonar cone. The arch results from a gradual decrease in distance to an object as it moves into the sonar cone. The distance to an object changes due to the conical shape of the sonar beam, which causes the distance to be greater at the edges of the beam, than at the center of the beam. When this distance change is graphed on the display an arch appears. |
Fish Symbol | A Fish Symbol is the graphic that is displayed on the screen when a Fish ID+ determines a sonar return is likely a fish. See also: Fish ID+ |
Fish ID+ | Fish ID+ is a Humminbird feature that utilizes advanced sonar processing algorithms to determine if a detected object is likely a fish. When the sonar signal from an object meets strict parameters, the unit draws a Fish Symbol (or icon) and the digital depth of the target. On DualBeam and DualBeam PLUS units, fish detected in the narrow center beam are shown as a blackened symbol, and fish detected in the wider beam are shown as hollow symbol. |
Feature Memory | Feature Memory is a Humminbird feature that retains the user’s menu settings in permanent memory. Settings are retained even when the unit is powered off indefinitely. |
Frequency | Frequency is the number of sound wave cycles per second of the sound impulse transmitted into the water. Typical frequency for fishfinder is 200kHz which offers a good balance of performance under many conditions. Lower frequencies such as 50kHz are capable of penetrating to greater depths but with less resolution. Higher frequencies such as 455kHz offer greatest resolution, but are limited in depth performance. Humminbird uses a variety of frequencies optimized for the application. |
Power Output | Power Output is the amount of sound energy emitted into the water by the sonar transmitter. Power output is measured using either RMS (Root Mean Square) or P-T-P (Peak-to-Peak) measurement systems. Either method is acceptable, however it is important when comparing power outputs to assure the same measurement system is being used, because P-T-P numbers are 8 times higher than RMS numbers. Greater power output allows the sonar signal to penetrate through weeds and thermoclines, reach deeper depths and operate more effectively in noisy environments such as when running at high speed. Humminbird utilizes sonar transmitters that vary the power output to provide optimum performance for the conditions. For clarity, Humminbird always quotes both RMS and P-T-P measurements. |
Pixels | Pixels are the “picture elements”, or small square blocks, that make up the image on the LCD display. Measured as a vertical by horizontal number (i.e. 640V x 320H), this key specification typically indicates the quality of resolution. In fishfinders, the total resolution (Vertical multiplied by Horizontal) is often less important than the “Vertical Pixel” resolution. See also Vertical Pixels. |
Pixels, Vertical | Vertical Pixels are number of vertical picture elements in a single column on an LCD display. A greater number of vertical pixels provide finer resolution of targets detected by sonar. Essentially, a vertical distance (the depth) when divided by a larger number breaks that distance into smaller samples, each representing a smaller area and thus providing more detail. In fishfinders, vertical pixels are more critical than horizontal pixels because the horizontal axis of the display represents time, or history. Sonar information on the horizontal axis can vary greatly depending on boat speed and the Chart Speed setting. A greater number of horizontal pixels show more sonar history that the boat has passed. On many models, Humminbird provides the most vertical pixels to provide the better display resolution. See also: Chart Speed, Pixels |
Pulse Width (Pulse Length) | Pulse Width is the length of time that a sonar sound burst is transmitted into the water. Shorter pulse widths provide better target separation, but can not travel to great depths. Longer pulse widths provide better depth penetration, but result in poorer target separation. Humminbird varies pulse width based on depth to optimize both target separation and depth performance. See also: Target Separation. |
QuadraBeam | QuadraBeam is a Humminbird sonar configuration that utilizes four sonar beams for a more detailed bottom image. QuadraBeam utilizes the DualBeam PLUS configuration for down looking, and also adds a two additional beams to look to the left and right. The sonar beams pointing to the left and right provide the ability to spot fish and structure over a wide 90° area, and to identify which side of the boat they are located. See also: DualBeam PLUS |
Quick Disconnect Mount | Quick Disconnect Mounting System is an exclusive Humminbird feature that permits the unit to be easily removed from the mount base by pressing a release button, and re-installed by simply snapping it into place. All cable connections are made when installing, so no separate wiring connections are required. Additionally, the mount offers 90° tilt and 360° swivel capability to adjust the viewing angle of the unit as you move about boat. |
Real Time Sonar | Real Time Sonar is a Humminbird technology that delivers ultra-fast sonar transmitter/receiver operation and results in a more detailed instantaneous view of what is under the boat. The Real Time Sonar window is a vertical band at the right side of the display that shows the instantaneous sonar return from the transducer at a particular instant. The RTS Window menu option permits the user to adjust the window to show the full sonar signal return, or just a narrower band that indicates intensity using grayscale. Real Time sonar relies on very fast Sonar Update Rate (Ping Speed). See also: Update Rate |
Side Imaging Sonar | Side Imaging (SI) sonar is an exclusive Humminbird sonar configuration that provides the most detailed image of the bottom available to recreational anglers. SI utilizes sonar beams that very wide “side-to-side”, but very “narrow” front to back (picture a knife blade). Due to the very narrow front to back beam angle, the objects on the bottom are imaged with very thin slices, and are shown on the display with great detail. The beams are also very wide and point both left and right, providing up to a full 180° (shows everything) of coverage of the bottom. |
Single Beam | Single Beam is a sonar configuration that utilizes only one beam looking straight down into the water. This is the most simplistic sonar configuration. Single beam systems are effective, however, trade offs must be made when selecting the cone angle (beam angle) between wide or narrow cones. Wide cones show more of the water for better target detection, but lack bottom detail. Narrow cones show better bottom detail, but lack wide coverage. Humminbird Dual Beam and DualBeam PLUS, QuadraBeam, 3D and Side Imaging systems overcome the limitations of simplistic single beam systems. |
SONAR | SONAR is an acronym for Sound and Navigation Ranging. Sonar technology utilizes precision sound bursts transmitted into the water to determine the distance and other attributes of objects in the water. Distance can be determined because the speed of sound in water is constant, and the time for the signal to return is measure, thus a simple mathematical calculation permits determination of distance. Also, sound travels very quickly in the water, making sonar a responsive, cost effective tool. Sonar is the basic technology behind all recreational and commercial fishfindering and depthfinding devices. |
Sonar Echo Enhancement | Sonar Echo Enhancement is a Humminbird feature that describes the high degree of sonar sensitivity achieved through a combination of transmitter/receiver and software algorithms. The result of Sonar Echo Enhancement is to display virtually everything in the water that is of interest to the angler, including bait fish, game fish, thermoclines, weed beds, subtle structure and more. |
Second Return | The Second Return is a term that describes the appearance of a second sonar return below the primary sonar return (bottom contour) at exactly twice the true depth. The second return is caused by the some sonar energy bouncing off the bottom once, rebounding to the water surface and then traveling back down to the bottom to be reflected again. Second returns are more common in shallow water and over hard bottoms; it is actually possible to see a third sonar return under some circumstances. The second return provides useful information to help determine bottom hardness, as areas with harder bottoms will generally create a second return. The second return can be used as a guide to set Sensitivity when in shallower water. |
Sonar Update Rate | Sonar Update Rate is the number of times per second that the transmitter/receiver sends and receives sonar signals. A very fast sonar update rates collect more information and provides a more detailed image of the bottom, fish and structure. Many Humminbird units operate at up to 40 times per second when in single frequency operation. Due the limitation of the speed of sound in water, the update rate begins to slow as depth increases above 50 feet. However, in very shallow water under 10 feet, update rates as much as 60 times per second can be achieved. |
Sensitivity | Sensitivity is a user feature that adjusts the sensitivity of the sonar system to show more or less detail in the water. Higher sensitivities are often preferred, however when the water contains debris (silt, storm debris, etc) it can be difficult to pick out targets. Conversely, if sensitivity is set too low, relevant targets can be missed. |
Speed | Speed is the rate at which the boat moves through the water (obviously). Boat speed can be measured as Speed Over Ground, or Speed Through Water. Speed Over Ground is provided by GPS, and is the measurement of boats progress across a given distance. Speed Through Water is provided by a speed paddlewheel, and the measurement of the flow past the boat, which may vary depending on current speed and direction. Speed Through Water is most critical for anglers using downriggers, as it impacts the running depth of the downriggers. Speed Over Ground is optimal for navigation, as accurate destination times can be derived from the measurement. Humminbird products allow for input and display of both sources. |
Structure | Structure is a general term for objects on the bottom that present a discontinuity and are a likely attractor for fish. This includes bottom contour features (drop-offs, humps, and holes), standing structure (stumps, timbers, brush piles) and a wide range of other potential objects (sunken boats, reefs). Humminbird units excel at showing structure with great detail over a wider area due to unique sonar configurations developed for the angler. |
Structure ID | Structure ID is a Humminbird feature that describes the traditional grayscale method of presenting sonar information. See also: Grayscale. |
Surface Clutter | Surface Clutter is sonar returns reflected off tiny objects near the surface of the water, including algae and even air bubbles. Typically, saltwater environments have significantly greater surface clutter than freshwater due to continuous wind and wave action causing aeration at the surface. The Surface Clutter menu provides manual control to bias the default settings under extreme conditions. |
Target Separation | Target Separation is the measurement of minimum distance that a fishfinder can discriminate two very close objects as separate targets. (i.e. two fish hanging very close, or a fish hanging very close to structure.) Humminbird fishfinders provide a very good 2 ½ inches of target separation in under 100 feet of depth. Target separation decreases as depth increases due to the need for longer Pulse Width to achieve greater depth. See also: Pulse Width. |
Thermoclines | Thermoclines are water layer(s) of distinctly different temperature that create a sonar reflection due to the density of the differing water temperatures. Typically a thermocline will appear as a continuous band across the display above at some distance above the bottom contour. Thermoclines are of interest to anglers because fish will suspend above or below the thermocline as they seek the optimum temperature and oxygen levels. |
Time Variable Gain | Time Variable Gain is a processing step applied to the sonar return to “normalize” the data so that objects of equal size (i.e. fish) appear to be the same size, even if they are separated by a good distance. Time Variable Gain is a fundamental attribute of good sonar, but is often promoted as a feature. Also called Depth Controlled Gain by some competitors. |
Transducer | The transducer is the part of the sonar system that mounts in contact with the water, and converts the electrical energy from the transmitter into sound energy which forms the sonar beam. Internally, the transducer consists of one or more piezo electric disks that physically expand very minute amounts to create the sound wave. This element also works in reverse, converting the returned sound energy back into an electrical signal that the receiver interprets. Transducers are available for many specific mounting applications for the boat such a transom mount, trolling motor mount, etc. Humminbird offers many sophisticated transducers, often with multiple piezo electric elements designed to form specifically shaped sonar beams, providing the angler with superior tools for finding and catching fish. See also Transmitter, Sonar Beam, Dual Beam, QuadraBeam, Side Imaging |
Transmitter | The transmitter and receiver are matched parts of the sonar system that send (transmit), listen to (receive) the sonar signals, and work in conjunction with the transducer. Humminbird transmitters are extremely fast cycling design that can send signals up to 60 times per second, as well as produce the varying levels of power output needed for depth different depths and conditions. Additionally, the transmitter has the capability to create very precise sonar pulses needed for a high degree of target separation. Humminbird receivers are extremely sensitive, but within a narrow “bandwidth” to discriminate against noise from external sources. Additionally, the receiver offers a wide “dynamic range” which provides the ability to alternatively receive very strong signals and very weak signals, without the strong signal overwhelming the weak signal. See also: Pulse Width, Transducer |
TripLog | Triplog is a Humminbird feature that provides an on-screen counter for Elapsed Time, Average Speed and Total Distance traveled. Requires a speed input to activate the feature. Triplog appears on the Large Digits View, and can be reset to zero through the TripLog menu. |
TruArch | TruArch is a Humminbird feature that provides true fish arches, not artificial arches or symbols. Humminbird units are capable of producing fish arches due to the wide 60° sonar beam of DualBeam PLUS, and extremely sensitive sonar receiver. See also: Fish Arch |
Total Screen Update | A Humminbird feature that refreshes and updates all the sonar information on the display when a range change occurs. Without Total Screen Update, only the most recent sonar information would be drawn to the new range, and the old sonar information would continue to scroll off the screen at the old range. |
Receiver | See Transmitter |
Views | Views is a general Humminbird term that describes the display image and presentation. The “2D View” shows traditional graphing sonar similar to most fishfinders, whereas the “3D View” shows the unique Humminbird three dimensional representation of the bottom. Other views include Zoom, Large Digits, and a variety of split screen views. |
Viewing Angle | Viewing Angle is an attribute of an LCD that characterizes visibility of the display when viewing from off the central access, such as when standing to the side of the product. Wider viewing angles are better because the information remains visible even when viewing from the side. |
WhiteLine | Whiteline is Humminbird feature that highlights the strongest sonar returns on the display using a very light gray band. This is preferred by some anglers who have grown accustomed to the feature on paper graphs chart recorders. Whiteline is similar to the competitive feature called Grayline. |
Wide Side | Wide Side is a Humminbird sonar configuration used in an optional transducer. Wide Side uses three sonar beams pointing to the left, right and down. Beams pointing to the left and right are effective for spotting fish and structure near the surface or on the bank. The down looking beam provides depth information directly below the boat. |
X-Press Menu | X-Press menus are Humminbird feature that makes the most commonly used menu selections available with one press the menu button. Items that appear on the X-Press Menu are related to the current view to present the most logical choices. Sonar View X-Press menus will differ from Chart View X-Press menus, etc. X-Press Menus are one of the principle reasons Humminbird products are easier to use. |
Zoom | Zoom is a feature that focuses in on a smaller area of the bottom (or anywhere in the water column) to provide enhanced resolution. With enhanced resolution, the angler can more easily see fish hanging in structure or multiple fish hanging close together. Zoom can be Full Screen or Split Screen, depending on the fishfinder. Split screen zoom divides the display into the full range view on the right, and the zoomed view on the left. Humminbird offers One-Touch Zoom which allows the zoom feature to be easily accessed from the regular sonar view with just one key press, eliminating the need to use menus to access the feature. |
Zoom, Bottom Lock | Bottom Lock Zoom is a feature that focuses on a smaller area just above the bottom to provide enhanced resolution. Unlike regular zoom, it continuously graphs the bottom at a constant point on the display regardless of changes in depth. This “flattens” out the bottom contour, however, it is effective at showing fish on or near the bottom, and is preferred by many saltwater anglers. |
Terminology Guide - GPS
GPS & Navigation Reference:
Acquisition Time | Acquisition Time is the length of time that a GPS receiver typically takes to determine the position from at least 3 satellites. Humminbird GPS Receivers provide very fast acquisition times of well under one minute, permitting users to get out on the water faster. |
Alarm, Arrival |
Arrival Alarm is the audible alert that sounds when the boat is equal to or less than the alarm setting (25 feet – 3000 feet) from the location of the destination waypoint. |
Alarm, Drift | Drift Alarm is an audible alert that sounds when the boat is equal to or over the alarm setting (25 feet – 3000 feet) from the location that the alarm was turned on. |
Alarm, Off-Course | Drift Alarm is an audible alert that sounds when the boat’s distance from the intended Track, or Cross Track Error, is equal to or over the alarm setting (25 feet – 3000 feet). See also: Track, Cross Track Error |
Altitude | Altitude measures height above sea level. Altitude is a measurement that can be provided by GPS. |
Altitude Bearing (BRG) | Bearing the direction to a destination waypoint measured in degrees from north (i.e. 321°, where 000° is North, 090° East, 180° is South, 270° is West). |
Chartplotter | Chartplotter describes a navigation device that shows Present Position on a Map, along with Tracks, Waypoints, and Routes. All Chartplotters are also considered Trackplotters. All Humminbird GPS Combo units are Chartplotters. See also: Trackplotter. |
Cold Start | Cold Start refers to the procedure that a GPS receiver must take when it does not have historical information regarding its current location. This procedure typically takes several minutes, and may be experienced upon first power up of the device, or if the device has been moved a great distance. |
Course Over Ground (COG) | Course Over Ground is the current direction the boat is traveling measured in degrees from north (i.e. 321°, where 000° is North, 090° East, 180° is South, 270° is West). When the Course Over Ground is equal to Bearing, the boat is said to be “On Course” and will arrive at the destination in the most efficient manner. COG is often confused with Heading. See also: Heading. |
Cross Track Error (XTE) | Cross Track Error is the straight line distance of the boat from the intended Track. XTE measures the how far the boat is off course, and is also the measurement that triggers that the Off Course Alarm. See also: Tracks |
Differential GPS (DGPS) | Differential GPS is a system to improve the position accuracy of the Department of Defense GPS through the use of secondary “correction signals” broadcast from ground stations around the coastal USA and on some inland waterways. These correction signals are provided by the USCG, and received by an auxiliary Differential Beacon Receiver (DBR) that connects to the GPS receiver. The advent of WAAS has largely negated the need for the added expense of a DBR (very expensive) in the USA. |
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Distance To Go | Distance To Go is the straight line distance between Present Position and the Destination Waypoint. DTG and SOG (Speed Over Ground) are used to calculate Time To Go. See also; Time to Go, Speed Over Ground |
Estimated Position Error (EPE) | Estimated Position Error is a calculation that indicates the potential position inaccuracy the user may experience due to a variety of GPS factors including satellite position in the sky, signal strength and others factors. |
Fix Type | Fix Type indicates whether the GPS receiver is providing 2D fix, or 3D fix. A 2D fix requires only 3 satellites and provides only latitude and longitude. A 3D fix requires 4 or more satellites, and provides latitude, longitude and altitude. |
GPS | GPS is an acronym for Global Positioning System. GPS provides accurate position (latitude, longitude, altitude) information virtually anywhere on the earth through satellite technology and personal receivers on the earth. A series geosynchronous satellites broadcast a unique signal toward the earth once per second. A GPS Receiver, such as those included with many Humminbird products, receives the signals from these satellites and is able to determine position based on very slight differences in the time each signal is received, and the receiver’s knowledge of the location of each of the satellites. |
Heading | Heading describes the direction the boat is pointing and is measured in degrees (i.e. 321°, where 000° is North, 090° East, 180° is South, 270° is West). Due to wind and waves, the boat is often traveling a slightly different direction than it is heading, and therefore Heading is often confused with Course Over Ground. See also: Course Over Ground |
North, True | North is the principle reference point of the compass (i.e. North is 000°). True North uses the axis of rotation of the earth as the reference for north and is constant for all points on the earth. Most GPS units default to True North as the setting. The GPS heading may vary from the boat compass heading because the compass uses Magnetic North. Humminbird GPS units provide the option of selecting True or Magnetic readouts by using the North Reference menu. See also: Magnetic North. |
North, Magnetic | North is the principle reference point of the compass (i.e. North is 000°). Magnetic North relies on the earth’s magnetic field to align a metal pointer generally towards True North. However, due to local variations in the earth’s magnetic field around the globe, the difference between True North and Magnetic North can up over 10°. |
Map Datum | A Map Datum refers to a particular survey of the earth’s surface that was referenced when creating a chart (i.e. WGS84). Since the earth is not flat, and not even consistently round, a mathematical model must be used to translate coordinates from the sphere of the earth to flat surface (a chart). This mathematical model is the Map Datum. Many different Map Datums have been used historically and around the world to create maps; often reference to the Datum can be found in the legend of the paper map. It is important to select the correct Map Datum in the unit when comparing GPS position to a paper chart, otherwise slight position inaccuracies can occur. Virtually all electronics charts utilize the WGS84 Map Datum and no setting changes are needed. |
MMC | MMC is an acronym for Multi Media Card. An MMC is postage stamp sized memory device used to store electronic data such a maps, waypoints, routes and other information. MMC is a very rugged format suitable for marine environment, but is not waterproof so some care should be used. The MMC is removable from Humminbird products, and can be used in a PC that is equipped with an appropriate “reader”. MMC is the same format many digital cameras use. See also: SD |
Present Position | Present Position is the current location (latitude, longitude) determined by GPS. The Present Position is indicated on-screen by a directional boat icon if moving, or a round symbol if stationary. |
SD | SD is an acronym for Secure Digital. An SD card is virtually identical in function to an MMC, however, the speed at which information can be accessed is generally faster, the storage capacity is generally larger, and card has security features which can be used to prevent copying the data from the card. SD is the same format many digital cameras use. |
Selective Availability | Selective Availability (SA) is a GPS system “feature” that can be implemented by the US Department of Defense (DOD) to degrade the accuracy of GPS positioning information. With SA active, the GPS provides accuracy of within 100 meters 95% of the time. With SA inactive, the GPS provides accuracy of within 45 meters 95% of the time. Currently, SA is inactive and consumer can enjoy the greater precision GPS provides; however, the DOD reserves the right to activate SA at any time. |
Speed Over Ground (SOG) | Speed Over Ground is the measurement of boats progress across a given distance, and is the speed measurement provided by GPS. An alternative “Speed Through Water” is provided by a speed paddlewheel, and the measurement of the flow past the boat, which may vary depending on current speed and direction. Speed Over Ground is optimal for navigation because accurate destination times can be derived from the measurement. Humminbird products allow for input and display of both sources. |
Route | A Route is series a waypoints linked together in a specific sequence to define a navigation path between two points, and saved in the unit’s memory. Routes are often used when frequently traveling between two or more locations because it is a faster and more accurate method than repeatedly selecting the individual waypoints each time one travels through the same area. Routes consist of a Start Waypoint, End Waypoint, and a series of waypoints between. Users can begin navigation at the beginning, or end (to run the route in reverse) or any point in between. See also: Waypoint |
Time To Go (TTG) | Time To Go is the estimated time required to reach the destination waypoint. TTG is calculated using the SOG and DTG. See also: |
Track Line (TRK) | The Track Line is desired the line the travel between two waypoints, and represents the most efficient path between the two points because it is a straight line. The TRK is measured in degrees (i.e. 321°, where 000° is North, 090° East, 180° is South, 270° is West). See also: Cross Track Error, Course Over Ground |
Tracks | A Track is a series of saved points that define the past path of the boat. These Track Points are saved at regular time intervals. Tracks are useful and quick method of see where you’ve been, and an easy guide to follow to get you back to the starting point. Generally, all GPS units have a limited number of Track Points that can be saved before the unit runs out of memory, and begins erasing the first track points saved. Because of this, the user can adjust the Track Point Interval menu to increase the amount of time between when points are saved, and thus extend the distance over which a track can extend. Tracks can also be permanently saved to memory, and re-displayed at the user’s option. |
Trackplotter | Chartplotter describes a navigation device that shows Present Position, along with Track, Waypoint, and Routes, but NO MAP in the background. See also: Chartplotter |
Trolling Grid | Trolling Grid is a Humminbird feature that displays a precise reference grid around a waypoint. This grid is used as a guide pattern for trolling around a specific area to assure a more efficient and complete coverage of an area. Trolling Grid resolution be changed by zooming in or out on the chart. Additionally, the Trolling Grid can be rotated on the display to orient it for optimal boat course for wave and wind conditions. |
UTC | UTC is an acronym for Universal Time Constant. UTC is the “standard time” used in navigation, and is the local time in Greenwich England. (UTC is equivalent to Greenwich Mean Time (GMT)). To display the correct Local Time in a Humminbird GPS unit, the user must use the Local Time Zone menu and select the time zone (i.e. EST, CST) |
WAAS | WAAS is an acronym for Wide Area Augmentation System. WAAS is complementary technology to GPS that provides enhanced accuracy through correction signals broadcast from Federal Aviation Administration WAAS satellites stationed over the USA. These secondary signals are automatically received by the standard Humminbird GPS Receiver. With WAAS signal, GPS accuracy is improved to 3 meters 95% of the time. Outside the USA, regional governmental coalitions have created similar systems such as EGNOS (Europe) and MSAS (Japan). |
Waypoint | A Waypoint is the saved location (latitude, longitude) of a point of interest that stored in a GPS units memory. This can include a marker buoy, dock, fishing hole or anything else the user may want to return to. Humminbird products offer the ability to name and assign a symbol to the saved location. Additionally, Depth, Date and Time of Day when then waypoint is created is also saved. |
Waypoint Target | Waypoint Target is a Humminbird feature that displays a precise “bulls eye” around a selected waypoint. This bull’s eye is used to easily monitor boat position relative to a waypoint, and is useful for fishing over submerged structure. With Waypoint Targets, a quick look at the screen lets you know how far off the waypoint the boat has drifted. |