Теоретические основы использования картографических проекций при создании электронных карт
Рассмотрены особенности составления электронных карт с использованием геоинформационных технологий. Дан анализ применения картографических проекций в зависимости от назначения данных видов карт. Указано на целесообразность создания и использования специального архива аэроснимков и космических снимков в целях более точного составления электронных карт.
In the modern period, information technologies used in cartographic science allow not only to clearly draw the contours of certain objects on the map, but also to introduce changes depending on the required scale. In addition, it is technically possible to link objects with geographical location and various attributes (information about organizations located in this building, the number of its floors, addresses). The above features give the created electronic maps multi-dimensionality and multi-scale, integrating a large volume of reference databases into them at the same time. Modern software products – geoinformation systems (GIS) are actively used to process a significant array of information and clearly present it, in accordance with the set goals .
In the digital map layouts used in web mapping, cartographic projections are taken as a basis, which receive changed names. In accordance with GIS technologies, these projections also have codes in the EPSG system, numbers in the electronic libraries of compiled and user GIS, sets of digital parameters. Digital cartographic projections have found application in numerous web mapping and web geoinformation services.
In mathematical cartography, almost all existing cartographic projections are divided according to three main features into the following classes: the type of normal grid (that is, the shape of the "auxiliary" surface: cylinder, cone, plane); the type of distortion and the position of the pole of the spherical coordinate system used (the position of the "auxiliary" surface relative to an ellipsoid or sphere).
According to the first feature, they are divided into three main classes: cylindrical, conical and azimuthal, where the auxiliary surface in them has the shape of a plane touching an ellipsoid (sphere) at the pole point. There are several subspecies similar to them: pseudocylindrical, pseudoconic and polyconic.
According to the type of distortion, projections are divided into equiangular (not distorting horizontal angles, but distorting lengths and areas), equi-large (not distorting areas, but distorting angles and lengths) and equi-intermediate (not distorting only meridian lengths), belonging to the class of arbitrary projections.
According to the position of the pole of the spheroidal polar coordinate system, projections are divided into: normal (the poles of the spheroidal and geographical systems coincide), transverse (the pole is located on the line of the geographical equator), oblique (the pole is located between the geographical pole and the equator) .
Geographical maps contains a certain set of information about the natural and socio-economic objects shown on the map, their location, properties. It can be divided into separate geographical elements by homogeneous groups of objects shown on the map. For example, the elements of the content of topographic maps are: geodetic reference points, waters, the relief of the Earth's surface, vegetation, soils, settlements, communication routes and means of communication. The mathematical basis that defines the mathematical laws of map construction and the geometric properties of the cartographic image establishes a coordinate relationship between objects in nature and their image on the map. The mathematical basis includes a cartographic projection, a coordinate grid (or grids), a scale and a reference geodetic network. The reference geodetic network provides a transition from the physical surface of the Earth to the surface of the ellipsoid and the correct position of the geographical elements of the map relative to the coordinate grid. The geodetic network required during the filming process is usually shown on topographic maps and thus included in their content.
It is well known that the electronic map is based on one or another way of displaying the earth's surface on a plane. For example, the cartographic projection that is selected for the construction of an electronic map directly depends on its purpose. For public maps and navigation maps, a Mercator projection with the WGS-84 coordinate system is used . For large-scale maps, both zonal equiangular projections (Gauss-Kruger) and non-equiangular projections (conic equidistant projection) are used to depict all linear distortions.
The research work of specialists leads to the conclusion that each cartographic projection has a set of certain parameters that allow you to accurately determine the origin of coordinates relative to the studied territory. It should be noted that angular parameters are determined by units of measurement of the geographical coordinate system, and linear parameters are determined by units of measurement of the coordinate system.
Technologies for creating and updating electronic topographic and special maps and other types of digital terrain information based on aerial and space surveys were implemented in the hardware and software complex for creating and updating digital terrain information, which is currently being used, a complex entirely built on domestic software.
The product is a hardware and software complex consisting of hardware and software tools connected by a local area network. The complex provides the ability to create and update digital orthophotoplanes of any scale and digital terrain relief matrices, image recognition of objects, determination of their quantitative and qualitative characteristics using automated stereoscopic decryption, storage of geospatial data in text and tabular form.
Currently, tools and technologies for creating electronic maps based on an object-oriented spatial database have been developed. The main advantages that this system provides for solving problems in automated cartography in comparison with currently existing technologies include the possibility of solving on the basis of fundamentally new approaches to creating various user models based on basic information using generalization technology. In an object-oriented data model, any objects are described by classes. Objects are characterized by properties or attributes that define their state, and methods (i.e. operations) that define their behavior. Objects interact with each other by transmitting the corresponding messages.
In the era of digital technologies, electronic maps are created on the basis of aerial photography and satellite photographs . For high-quality display of the necessary objects on electronic maps, it is advisable to create a special archive of aerial photographs and satellite images. With the help of this archive, in addition to large-scale maps of the territory, schemes of individual objects and plots are also compiled. At the same time, depending on the mapped area and the required scale, the corresponding cartographic projection is also used.
As a basic approach to the development of an automated information system (AIS), the concept of a geoinformation system (GIS) has been adopted, which assumes the spatial placement of the described objects and their coordinate reference on the ground. The use of this concept in the implementation of AIS is determined by the requirements that it must meet, namely: the land resource must be represented graphically in conjunction with semantic data. The graphical representation should be organized in the form of a planar and spatial model with the ability to determine coordinates when specifying any point on the screen display of this model.
The solution of any urban planning task - from the placement of a building on the territory of the city, the development of a city master plan to a district planning project – requires reliable comprehensive information from the field of geodesy and cartography, photogrammetry, environmental protection, land use, data on the population and development of the planned territory, on engineering and transport infrastructure, on the ownership and condition of the fund of buildings and structures, as well as on the adopted planning, technical, legislative decisions on the further development of the territory.
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- World Geodetic System – 1984 (WGS-84) Manual – Montreal: International Civil Aviation Organization. 2002.
- Александров Ю.С. и др. О новых подходах в технологиях создания электронных (цифровых) карт // Геоинформатика и картография.2022.no.4.