Map is based on certain mathematical rules, the object (usually referring to the Earth, but also includes other stars) on the geographic information, through scientific generalization, and the use of a particular system of signs that a certain vector graphics in order to pass their number and quality of time and space on the distribution and development and changes.
Map according to their content can be divided into general maps and thematic maps two categories. Normal maps are integrated, said the Earth's surface, the main natural and socio-economic phenomenon of the general characteristics of the map. Thematic map is based on professional needs, highlights the theme of one or several elements or a map of the phenomenon. One of the elements of the theme made it very detailed, while other elements around the theme of the need to express, as a broad geographical basis that if the geological maps, land-use maps, traffic maps and so on.
A variety of objects in the Earth's surface, a wide range of different forms, but generally can be divided into surface features and landscapes on the two human beings. Where the ground to form a variety of natural and artificial fixity of the objects, such as roads, housing, railways, rivers, lakes, forests, grasslands and other types of artificial structures, are known as surface features. The Earth's surface shape and appearance of the various ups and downs, such as mountains, deep valleys, scarp, cliffs and rain crack gully and so on, known as the landscape. Referred to as terrain surface features and landscapes.
Reduced by a certain scale, after a comprehensive trade-offs will be a variety of surface features and landscapes on the ground plane location and height of a certain mathematical rules, represented by symbols with the provisions of the projection map, known as the topographic maps. Large-scale topographic maps generally use the orthographic projection. Topographic map is a general map. If the tub only said that the shape and surface features, said ground-plane location of ups and downs without a map, then known as the plan.
Among the various project planning, design stage, need to topographic maps, especially the large-scale topographic maps can provide information about the construction of white natural topography of the region structure and environment, etc., in order to make the planning, design in line with the actual situation. Therefore, topographic maps is to formulate the plans for construction projects, establish an important basis and foundation of CIS data. The correct use of knowledge maps and topographic map is related to engineering and technical personnel must possess one of the basic skills.
Second, the contents of the topographic map
Reflected on the topographic map, including the earth's surface, almost all the objects and phenomena, they not only full of natural phenomena (such as soil and vegetation, water, geomorphology, etc.), but also a social phenomenon (such as residential areas, an independent surface features, roads, state, etc.); is visible not only the specific things (such as surface features, topography, etc.), but also is not visible (such as river depth and bottom quality, undercurrents, etc.), abstract (such as the residents and in control point name and grade, wells and lakes, water quality, voltage, etc.) phenomena; no instrument can be a static phenomenon, but also can be a phenomenon of movement (such as velocity, flow, etc.) has really vary in content, species diversity. However, because of the terrain map is an attempt to profile as a regional scale mapping, so topographic contour map can be divided into elements and map profiles within the two major external factors are of large-scale topographic maps, for example, its elements be summed up, are shown in Figure 2-1-1.




In the medium and small-scale topographic maps, map profile Notes, maps, information on the contents and supporting graphics are very abundant. Note contour map which includes: Jingwei Network Notes, rectangular grid reference annotation, sector-side annotation, adjacency graph numbers, etc.; information includes: map name, map number, date and mapping mapping methods, coordinate systems and Height systems, contour intervals, based on schema, etc.; auxiliary graph includes: legend, linear scale, slope-foot, three northern access to the maps and charts neighborhood map. However, other scale topographic maps, map profile Notes, maps, charts and supporting information on the contents of small, only the above part of it.