Methods Of Comparative Plotting Of The Ship’s Position
Free (open access)
In recent years the problem of position plotting in navigation has been dominated by satellite systems, the GPS in particular. These systems are used both at sea (maritime navigation) and in the air (aerial navigation) as well as on land (terrestrial navigation). With the application of satellite systems the position can be plotted within very short spaces of time, in the range of a few or a dozen seconds. Relying exclusively on satellite systems, however, exposes to the danger of losing information in case of average, intentional switch-off, disturbance and possible encoding of information reaching the user. This results in the necessity of having yet another, autonomous system at one’s disposal (independent of external information sources) making possible the plotting of position in an autonomous way. These requirements are met by methods of comparative navigation. The object of interest of comparative navigation is plotting the ship’s position by comparing a dynamically registered image with a pattern image. The pattern images can be numeric radar charts, sonar or aerial, suitably prepared for comparison with respectively radar, sonar or aerial images. Yet the most frequently registered images at sea will be radar images; the pattern, on the other hand, will be a numeric radar chart generated on the basis of topographic and hydrometeorological data or previous radar observation. The article presents methods of computer ship’s position plotting by means of comparative methods.