What are the definitions of dot, line, and surface symbols?

Map symbols are the basic means of representing the content of the map, which is different in shape and size.

1. Colors are different from graphics and text. Map symbols are the language of maps and are a graphic language. Compared with the written language, the biggest feature of it is that the image is intuitive and clear at a glance.

In the case of individual symbols, it can represent the spatial location, size, quality, and quantity characteristics of each thing; As far as the same kind of symbols are concerned, it can reflect the distribution characteristics of various elements; The sum of various symbols can indicate the interrelationship between various elements and the overall characteristics of the region. Therefore, map symbols not only have the basic function of determining the spatial location, distribution characteristics, quality and quantity characteristics of objective things, but also have the special function of interconnecting and jointly expressing the overall characteristics of various elements of the geographical environment. In order to have a further understanding of the characteristics and functions of map symbols, the symbols can be divided into surface symbols, point symbols and linear symbols according to the distribution of objective things represented by the symbols.

A polygon symbol is a symbol that represents the distribution of things at a map scale. When the actual area is large and the outer outline can still be displayed after being reduced according to the map scale, the surface symbol is used to represent the objective object in a polygon shape. Such as large lakes, large forests, swamps, etc.

A polygon symbol is a contour line (solid, dashed, or dotted) that represents the distribution range of a thing, and its shape is similar to the flat shape of the thing. Colors or explanatory symbols are added to the outline to indicate its nature and quantity (Figure 3-1). For things represented by such symbols, the length, width, and area can be measured on a graph.

This symbol is also commonly referred to as proportional symbol.

The dotted symbol is a symbol used to express small areas (such as oil depots, weather stations, etc.) and dotted objects (such as the polygon symbol control points in Figure 3-1) that cannot be represented according to the scale. When some small but important things on the ground cannot be displayed after being reduced according to the map scale, they are represented by dot symbols. Theoretically, a dot symbol has neither shape nor size, but in order for it to be perceived, it must have a certain size and shape, and there must be a variation of color.

The shape and color of the dotted symbol indicate the nature of the thing, and the size of the dotted symbol usually reflects the hierarchical or quantitative characteristics of the thing (Figure 3-2). The shape of this symbol is independent of size and map scale, it only has positioning significance. This symbol is also commonly referred to as a non-proportional symbol.

A linear symbol is a symbol that expresses the distribution of things in the form of a line or ribbon. The length of things that extend in a line or ribbon on the ground, such as rivers, roads, boundary lines, etc., can be expressed in scale, while the width generally cannot be expressed in scale, and need to be appropriately exaggerated. The shape and color of the linear symbol represent the quality characteristics of the thing, and its width often reflects the rank or value of the thing (Fig. 3-3).

This kind of symbol can indicate the distribution position, extension form and length of things, but not its width, and is generally called semi-proportional symbols.

The representation of the map.

1.Point-like distribution elements: fixed-point notation method; Fixed-point symbols and symbols: Symbols of different shapes, colors and sizes are used to represent the independence of the symbols on the map.

, which is a representation of the quantitative and qualitative characteristics of the point-like distribution phenomenon.

2.Linear Distribution Elements: Linear Notation Method;

3.Polygon features include:

The phenomenon of continuous distribution and covering the cartographic area: the quality base method, the contour method (contour layered coloring method), and the positioning chart method;

The Blind Elephant of Intermittent Patchwork - Scope Method;

Discrete distribution of phenomena - point value method, partition chart method, hierarchical ratio method (range density method);

The phenomenon of the state of motion - the moving line method.

The so-called line symbol is a semi-scale symbol.

A linear symbol is a symbol that represents a concept that can be thought of as a line of space. The symbol extends in a certain direction, and its length is related to the map scale.

As a graphical representation method to represent various real objects and related phenomena in geographic space, map symbols have gradually become GIS (GE OgraphicInformation System, Geographic Information System).

One of the research hotspots in system and modern cartography, especially in the development of electronic chart system, the quality of its symbolic expression will directly affect the performance of the system. According to the different ways of representation of symbols on the map, symbols can be roughly divided into three categories: point symbols, line symbols and area symbols.

Among them, because the basic constituent unit of the linear symbol is the dot-like symbol, and the face-like symbol is composed of the linear symbol; Therefore, the linear symbol is widely used as a connecting symbol to connect the upper and lower levels. At the same time, line symbols are also one of the most complex classes of map symbols. Line symbols are generally composed of primitive primitives, which can be lines, polylines, or polygons.

as well as a variety of simple graphics. These primitive elements are grouped in a certain permutation.

way to draw or fill it into a line symbol.

Summary. Linear symbols: Symbols that express the phenomenon of lines or bands extending in a certain direction in space. It has positioning characteristics and is a semi-proportional symbol.

Polygon symbols: Symbols that express phenomena with a continuous two-dimensional distribution in space. It has positioning characteristics and is a proportional symbol.

What are the definitions of dot, line, and surface symbols?

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Linear symbols: Symbols that express the phenomenon of lines or bands extending in a certain direction in space. It has positioning characteristics and is a semi-proportional symbol.

Face-like symbols: Symbols that express the phenomenon of continuous two-dimensional distribution in space. It has positioning characteristics and is a proportional symbol.

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A "line symbol" is one that extends in a certain direction and its length is at the scale of the map.

The purpose of the map scale is as follows:

According to the scale on the map, the distance between the two places on the map can be measured; According to the actual distance and scale of the two places, the distance on the map of the two places can be calculated; The scale can be calculated based on the distance on the map and the actual distance between the two places.

Depending on the purpose of the map, the size of the area to be represented, the size of the map sheet, and the details of the content of the map, the scale used for mapping varies from one size to another. The numerator in the map scale is usually 1, and the larger its denominator, the smaller the scale. Usually a map with a scale greater than 1/100,000 can be called a large-scale map; Maps with a scale between 1/100,000 and 1/1 millionth are called medium-scale maps.

Maps with a scale of less than one millionth of the calendar are called small-scale maps. On the same map, the larger the scale, the smaller the scope of the map, the more detailed the content in the map, and the higher the accuracy. The smaller the scale, the larger the area represented on the map, the more concise the content reflected, and the less accurate it is. Most of the maps in geography textbooks and atlases used by middle school students are small-scale maps.

The main variables that describe the nature characteristics are: shape, color, structure, orientation; Secondary variables: lightness and density, which enhance the difference in their role.

1) Point symbol: It is the overall image of the object represented by the individual symbol, therefore:

a.Shape variables are the most vivid and intuitive factors in the shape of symbols.

b.Artistic pictograms and perspective symbols are a good way to represent the figurative characteristics of symbolic objects.

c.When there is no need to establish a direct visual connection, geometric shapes are used, which can express a certain meaning in terms of color, structure, etc.

d.Text or letter symbols: Hints at the concept of the nature of the cartographic object.

2) Linear symbols: Linear objects often express certain symbolic meanings through shapes, colors, and structural forms. Because the classification of linear symbols involves hierarchical differences, it is often necessary to use size, color, shape, and structural variables together.

3) Polygon symbols: Objects (such as soil, climate, or vegetation distribution, etc.) that are continuously distributed in a certain range in the form of polygons in geographical phenomena can appear in the form of polygon symbols. Differences in pixel shape, structure, orientation, etc., are used to describe the differences in the attributes of the area range.

Its basic composition can be geometric shapes or pictographic individual figures (with symbolic and associative effects). Structural changes can effectively expand the variety of symbols when filling area symbols. Color is another effective way to distinguish the nature of an area.