Surely the reader is familiar with these lines of both types of maps, vector and raster, and their images. If the differences in elementary images in both technologies are immediately noticeable, then when viewing map images, determining which type electronic cards are is not easy.
What are electronic maps, vector and raster maps, properties and differences.
Externally, vector and raster electronic maps can look exactly the same. The same contours and lines, the names of objects and the color-filled spaces of land and water areas. But it is necessary to significantly change the scale of images, as the picture will radically change. Blurring lines and other defects appear on the raster map. Commonly encountered when scanning images and taking photographs with a low-resolution digital camera. And what happens when you change the scale on a vector map displayed by the corresponding cartographic program?
Firstly, new details and objects appear on electronic cards. Which at a small scale was not, because they are on another information layer of the map. Of course, all lines and contours remained. But as they say, and that’s not all. When you hover over an object, a window pops up with a clear name of the object and its characteristics. This process, called the identification or recognition of an object, is very important for navigational use of the map. Each object of the vector map and its attributes have certain codes to which the navigation system should adequately respond when using it.
Additional information, which was not originally on the original paper map, can be placed on such electronic maps and geo-referenced. For example, about tides, currents, ports, weather forecasts and so on. In other words, the data associated with the electronic vector map form a cartographic and information database, which significantly expands the automation capabilities of navigation as a whole. Only in vector maps is it possible to unload maps from images of some physical objects that do not affect traffic safety. Thanks to what the card becomes evident and well readable.
A raster map is to a large extent just a “picture”. Of course, useful for observing the environment, but this all its advantages and capabilities are exhausted. Its scaling range is very narrow. Of course, a raster map can be used for navigation by marking the current location on it. But a number of important navigation tasks, such as generating warnings when approaching hazards, cannot be solved in systems using a raster map. Docking raster maps of different scales and converting projections and so on is difficult. They have significant limitations on how to configure the display on the screen. So, in them it is impossible to change the information load of the card and get a day and evening color palette acceptable from an ergonomic point of view.
A wide-scale vector map allows you to implement dynamic electronic navigation with the issuance of many current automatic alerts to the user, for example, when approaching a danger or reaching a destination. In systems with vector charts, there is a unique function for warning the skipper about a dangerous course and calculating safe course sectors. Thanks to the wide functionality of vector maps, currently all modern navigation systems use only them. For the new features of vector electronic maps, you have to pay the complexity of the logical structure of their data and the increased complexity of creating vector maps.
If receiving a raster map by scanning it is accessible to the mass user, then the creation of vector maps is carried out by professionals: cartographers, hydrographs and programmers. Since paper maps were the first historical carrier in the recent past of all cartographic data, electronic maps are usually created on their basis as electronic versions. But these are not electronic copies of paper cards, since additional information from various sources is included in electronic cards. When creating electronic cards, scanning and digitization of paper cards are used, followed by semi-automatic processing.
Due to the high complexity of the production of electronic cards, the creation of a collection of cards for the entire land area and the oceans is still far from complete. As an example, consider the elements of the technology for creating marine electronic cards from S-MAP. The initial fragment of the marine raster map is shown below, where the first stage of the process is shown, when only the coastline and lines of recommended paths are copied.
Then, individual layers are created for other objects, for example, for buoys and depth marks. A separate layer is distinguished for depth contours (isobaths), continuous depth contours are filled with a color shade. Entered and attached to the objects text information, for example, the characteristics of the means of navigation equipment.
A special layer is created for port information, another layer for tide information. The result is the final map, in black and white, shown in the figure below.
It should be noted that S-MAP maintains its collection of electronic cards with regular updates, which is delivered to all subscribers through various communication channels at any time of the day at no extra charge.
Based on materials from the book All About GPS Navigators.
Naiman V.S., Samoilov A.E., Ilyin N.R., Sheinis A.I..