Cartographic (topographic) conventional signs are symbolic background and line symbols for various terrain objects that are used on topographic maps and plans. These signs are characterized by a common designation of homogeneous groups of objects. It is observed both in color and in style. At the same time, the main signs used in compiling topographic maps of various states do not differ much from each other. As a rule, conventional signs convey the size and shape, location, as well as some quantitative and qualitative characteristics of objects, elements and contours of the relief, reproduced on maps. All of them are divided into areal (large-scale), off-scale, explanatory and linear. We briefly describe each of these types.
Large scale signs
Areal, or large-scale, conventional signs are used to depict those topographic objects that occupy a significant area. The sizes of these objects can be expressed in the scale of the plan or map. The area symbol has two components. The first of these is the border sign of the object. The second is conditional coloring or signs filling it. The dotted line shows the contour of the object (swamps, meadows, forests). The solid line shows the outline of the settlement, reservoir. In addition, the contour of the object can be depicted using the symbol of one or another border (hedges, ditches).
Fill characters
The symbols for the terrain plan are diverse. One of their types is fill characters, which are presented in a certain order inside the contour. The order may be arbitrary, chess. Filling characters can also be arranged in vertical or horizontal rows. Large-scale signs can not only find the place where the object is located. Thanks to them, you can also evaluate its shape, area, linear dimensions.
Scale Signs
This type is intended for the image of objects characterized by length on the ground. For example, this is a designation of a river, roads or railways, power lines, clearings, borders, streams, etc.
Linear signs
They occupy an intermediate position, being between extra-scale and large-scale signs. The length of the corresponding objects is estimated based on the scale of the map, but the width is outside it. Usually it is greater than the width of the terrain feature presented on the map, the position of which corresponds to the longitudinal axis of a symbol. Horizontal lines are also represented by linear signs.
We have not yet listed all the conventions of the terrain plan. We pass to the explanatory signs.
Explanatory signs
They are used to further characterize the objects shown on the map. For example, they denote the width, length and carrying capacity of the bridge, the nature and width of the road surface, the nature and depth of the ford ground, the average height and thickness of the trees in the forest. Explanatory are their own names of objects, as well as various inscriptions on maps. Each of these inscriptions is carried out in letters having a certain size and an installed font.
Generalized sign
As the topographic maps scale down, for convenience, homogeneous symbols of the plan of the area are combined into groups, which, in turn, are combined into one generalized sign. The notation system as a whole can be represented as a truncated pyramid. At its base are signs used for plans having a scale of 1: 500. Those that are used for maps with a scale of 1: 1 000 000 (they are called survey-topographic) are located at the top of this pyramid.
Color coding
For all maps of color, which have the symbols of the plan of the area, the same. It doesn’t matter what their scale is. Bar marks of structures, structures, land and their contours, strong points, local objects, borders are made in black. Brown denotes relief elements. Glaciers, watercourses, ponds and swamps on the map are blue (light blue is a mirror of the waters). Green is used when a forest symbol is presented. More precisely, it is used for trees and shrubs in general. Light green is used to denote vineyards, shrubs, dwarf forests, and dwarf forests. Highways, as well as neighborhoods characterized by fire-resistant buildings, are marked in orange. Yellow is used to indicate improved dirt roads, as well as neighborhoods that include non-flame retardant structures.
Abbreviations
For topographic maps, in addition to conventional signs, there are conditional abbreviations of the names of various political and administrative units. For example, the Moscow region is designated as Mosk. Also abbreviations are set for explanatory terms. The symbol of the swamp is Bol., Power plants - el.-st., south-west direction - SW. Using standardized fonts allows you to provide important information in addition to conventional symbols. For example, in the fonts used for the names of settlements, their political and administrative significance, type, and population are displayed. As for the rivers, information on the possibility of shipping and their size can be obtained. Fonts that are used to characterize wells and passes, elevations make it possible to understand which of them should be considered the main ones.
Terrain
On topographic maps and plans, the terrain is depicted using the following methods: colored plastics, washing, strokes, contours and elevations. On large-scale maps, it is usually marked by the contouring method, which has significant advantages over other methods.
Relative and absolute height
In order to correctly depict the relief of the earth's surface on the plan, you need to know what heights have points on it. There are lowlands, highlands, mountains on earth. How do you know how low or high they are? To do this, you need to compare the heights of these objects relative to any identical level. The surface of the sea or ocean is taken as the initial level.
Absolute altitude - a point on the earth's surface, which is measured from the level of the ocean or sea. If the points are located above this level, then their height is considered positive (for example, the designation of the top of the mountain is a positive number). Otherwise, it will be negative. Relative height is the difference in height from a point on the surface of the earth to another.
How are the signs installed
All conditional topographic designations must necessarily have expressiveness, clarity. They should, in addition, be easily drawn. Symbols on the map used for all scales are established by instructive and regulatory documents. They are mandatory for all departments and organizations that carry out filming work.
Land management organizations take into account the diversity of agricultural facilities and land. It often goes beyond the accepted mandatory symbols. Therefore, land management organizations from time to time issue additional signs that reflect the specifics of agriculture. So new symbols appear on the map.
Card Generalization
Local items, depending on the scale of plans or maps, are displayed with different details. For example, in a settlement on a plan having a scale of 1: 2000, only individual houses of the same type will not be depicted, but their shape will also be shown. But on a map with a scale of 1:50 000 there is an opportunity to present only quarters. What will happen if you increase it to 1: 1 000 000? In this case, the whole city will be depicted in a small circle. A generalization of maps is a generalization of relief elements that occurs when moving from larger to smaller scales.
Topographic designations, as you can see, are diverse. They help us get information about the objects presented on the map. Designations of cities, villages, rivers and forests, etc. significantly differ from each other. Not surprising, because these are completely different objects.
In conclusion, we will talk about such a concept as a terrain plan. It met several times in this article and may not be understood by the reader.
Terrain plan
In order to farm and study nature, images of land surface areas are needed. A small area can be photographed or drawn. Usually a photograph is taken from the earth's surface. Therefore, the near objects depicted on it obscure the distant ones. Both photography and drawing give us a certain idea of the area. However, one cannot see on them what shapes and sizes the site as a whole has. Objects that are placed on the surface will be better visible if you take a photograph of the site from above, say from an airplane. An image obtained in this way is called an aerial photograph. The objects presented on it are similar to how they look on the ground. Their relative positions and sizes will be visible in this image.
The terrain plan also conveys a top view. However, there are many differences between it and the photograph. The terrain plan is a drawing made on paper. It depicts in a reduced form a small area of the earth's surface. Plans differ from other images in that all the objects shown on them are shown with conventional signs. There are a lot of their varieties. The simplest of them, where only individual objects are depicted, are called schemes. A terrain plan is a type of topographic map.