For a while, Garmin produced wearable GPS navigators as ship’s for use when navigating the sea. In all their functions, they were similar to the stationary ship GPS navigators installed, but had a built-in database of coordinates of lighthouses and navigation signs along the American coast.
In addition, some Garmin portable GPS navigators intended for use at sea as a ship, unlike land analogs, had the Anchor Watch “Anchor Watch” function. It was possible to remember the point where you anchored and set a radius. If the anchor creeps and you drifted beyond the specified radius, the navigator gave an alarm.
Functions of marine and ship GPS navigators, chart plotters, their special features.
Mandatory for offshore and marine GPS devices, the MOB (Man over board) function is Man Overboard. As a rule, for wearable receivers, it is called by a combination of keys, and special marine navigators have a separate button for its quick call. When you click on it, the device remembers the scene as a waypoint called MOB and instantly turns on the navigation mode to this point.
What for? A fallen person in the waves can be seen, at best, for several tens of meters, or even less. If you lose a person, the chances of escape, even for a good swimmer, on the high seas are void. Subcooling, loss of consciousness, and death quickly ensue. The life of the fallen depends on how accurately and quickly you can return to the point of fall. On a small ship, everyone on board should be instructed in how to use the “Man Overboard” mode, and the GPS is always on and ready to go..
Functions such as XTE (Cross-Track Error), which are little used in ground orientation, are lateral displacement from the route and VMG (Velocity Made Good), and in some instruments, WCV (Waypoint Closure velocity) is useful or effective speed. They make sense at sea, becoming the navigator’s working tool. Using XTE, setting the route along the channel axis, you can quickly control your position in relation to its borders.
The sound alarm of ship navigators will warn about the departure of the width of the safe corridor of the user-defined width. Effective Speed helps you choose the best course for wind, wave, and current. For example, a vessel may go with a certain deviation from the direction to a waypoint, but at a more favorable angle to the wind, which allows it to develop greater speed, and arrive at its destination faster than if it were going in a straight line. This function is especially relevant for sailing ships..
Chartplotters, features and accessibility.
It is worth talking about them in more detail, as about ship devices with electronic cards that give advantages to the skipper. Marine chartplotters are even more different from their automotive counterparts. So, if Garmin car navigators work with Map Source maps, then marine navigators should support Blue Chart maps. A marine electronic chart contains completely different types of data. This is, first of all, depths and lines of equal depths, isobaths. The nature of the seabed (sand, silt, rock) must be indicated. For lighthouses, buoys, milestones and other means of navigation support (SSS, navaids), not only coordinates are given, but their color, shape, height and description of the lighthouse tower, detailed characteristics of lights, lighting sectors and operating mode.
The boundaries of the prohibited and permitted areas of navigation are indicated. Fairways, dimensions of navigable spans of bridges, information on tides, currents, textual information on local navigation rules and so on. A marine plotter should be able to read and display all this information. The amount of information on marine electronic charts is so large that a color display is extremely useful, if not necessary, for its operational perception. In color chart plotters, as a rule, you can choose one of several color palettes depending on the ambient lighting. Including nightly, non-glare colors.
High-contrast color displays of modern high-brightness chartplotters and with anti-reflective coating can be used even in bright sunshine, without shading screens and visors. A variety of on-screen pages facilitates the perception of information. One of the innovations is a multi-window interface that allows you to place information windows in any convenient place on the screen. In professional chartplotters, it is possible to simultaneously display two cartographic panels with different sections of the map.
For panels, you can set different scales and different orientation of the map. In marine ship plotters, a special map image mode, the relative motion mode, began to be applied. Chartplotters borrowed this mode from radar equipment. In the traditional mode of true movement, the image of the map is motionless, and the mark of the vessel moves. In this mode, you can scroll the map by moving the cursor with the joystick to the border of the map, thereby moving the map. This mode is convenient for viewing a navigation situation and planning a route. In relative motion mode, the ship’s mark is stationary, and the chart moves on the plotter display.
This mode is more convenient for analysis and assessment of the situation at the rate. In particular, to monitor the position of the vessel on the fairway and in cases of discrepancy with oncoming vessels. In ship chartplotters, a movable cursor, controlled by a joystick, handwheel or trackball, is necessarily provided. With its help, the distance and azimuth to any map object are measured. The geographical coordinates of objects are determined and reference information on their characteristics is obtained.
Measurements are taken from the current position of the vessel to the cursor position or between any two points marked with the same cursor on the map. The cursor creates and marks both individual waypoints and the routes containing them. Many advanced chart plotters can interpret depth chart information and give a shallow signal less than a given depth and course hazard. Another function – automatic verification of a route made by the user to safe depths, will also help to eliminate the influence of the human factor. Often, setting only the start and end point of the route, beginners lay it through dangerous shallows, or even by land.
That is why it is better to give preference to special marine devices with professional S-MAP, Transas, Navionics, Garmin Blue Chart vector charts from electronic-cartographic systems, rather than raster charts that only display a scanned image but do not understand information about depths and dangers. And of course, you should not swim on the home-made cards of pirate origin purchased on the market, which, unfortunately, happens.
Another important consideration here is the regular updating of maps. Finally, the functions of many instruments for receiving and displaying meteorological information are specifically marine. These are facsimile weather maps transmitted in analogue mode by radio. NAVTEX text radio messages (weather, navigation alerts, distress alerts, etc.). Meteorological service provided by Raymarine, Garmin (US coast) and C-MAP (C-Forecast, the Mediterranean Sea, the North and Middle Atlantic, the North and Baltic Seas).
Based on materials from the book All About GPS Navigators.
Naiman V.S., Samoilov A.E., Ilyin N.R., Sheinis A.I..