Basic concepts of GIS

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Let’s consider the basic concepts of GIS, which are present in one form or another in all modern geographic information systems.

Data

In GIS, data is divided into two categories:

  • spatial (location);
  • semantic (attributes).

This is probably the most important component of a gis courses melbourne. Position data and associated tabular data can be collected and prepared by the user, or purchased from suppliers on a commercial or other basis. In the process of managing spatial data, GIS integrates spatial data with other types and sources of data, and can also use the DBMS used by many organizations to organize and maintain the data at their disposal.

Objects

Spatial data includes geographic features represented by:

  • dots;
  • lines;
  • polygons.

Arcs describe those real objects that can be considered as lines. An arc consists of line segments and circular arcs.

Polygons are closed areas that represent areas that are homogeneous by some criteria.

Attribute data can include an object ID, any descriptive information from databases, an image, and more.

Layer

Layers in the map are divided into two main types – raster and vector.

Vector layers are a collection of simple geometric objects (point, arc, polygon) that represent certain objects on the ground. Feature layers can also store topology, i.e. information about the relative position of objects.

Raster layers are solid images. They cannot contain objects. However, they can serve as backgrounds for vector layers.

Layer object

Each object of a vector layer can correspond to a record in the database, which ensures the binding of information to the terrain. This correspondence can be ensured in particular by assigning a corresponding identifier to each object.

Map legend

Map Legend is a collection of map symbols, with textual explanations to them. Usually, legends are created on the basis of classifications of depicted objects and phenomena, they become their graphic model and often serve to build classifiers.

Map

It is a collection of geographic layers, each of which brings information to the map on a specific topic. For example, a layer of rivers can be applied to a layer of boundaries of a certain territory, then a layer that displays the amount of atmospheric precipitation as a percentage, etc.

An electronic map in a GIS can be viewed as a multi-component reality model. The main goals of its creation are:

  • Graphic communication of spatial relationships and disputes

divisions;

  • Improving the ability to analyze, process and display geogra

physical information data;

  • Visual display of digital models of invisible phenomena

for the human eye;

  • Automation of display and cartographic analysis in the system

swing control; study of objects, phenomena and processes taking into account

the volume of the dynamics of their development and possible use;

  • Obtaining analytical solutions in graphical form in modes

real and shared time, etc.

Layered data organization

The concept of layered representation of graphical information is borrowed from CAD systems, but in GIS it has received a qualitatively new development. Technologically, the organization of layers is based on data typing. A lot of different data has different characteristics and in the process of visual processing this set can be overloaded with information. To reduce the information load on the operator, graphic data is typed and combined into layers. Thus, layering simplifies the processing process and improves its quality. Layers in GIS can be both vector and raster, and vector layers must have one of three characteristics of vector data. Those. vector layer must be defined as point, line or polygon in addition to its thematic focus.

Each layer can be used both separately and in a complex. (Fig. 4) With the help of a system of filters or specified parameters, objects belonging to the layer can be simultaneously scaled, moved, copied, recorded in the database. In other cases (when setting other modes), you can prohibit editing of layer objects, prohibit their viewing, or make them invisible. The introduction of topological properties into graphical GIS data allows you to solve many problems.

Visual processing of information in GIS

One of the contradictions of the majority of existing information systems is the contradiction between high-speed data processing in a computer environment and low bandwidth of the “man-computer” channel, especially in interactive processing modes. Various approaches have been proposed to improve the performance of interactive processing. One of these is a method of visual information processing, based on the selection and generalization of the necessary data and their presentation in a visual form. Data, presentation in graphical form allows you to identify individual phenomena orders of magnitude faster than the analysis of tabular or textual information. The effectiveness of visual information processing is expressed in the fact that it allows you to connect the reserves of figurative, associative thinking to active decision-making.

Representation of a situation in the form of images summarizes information and allows a specialist in a given subject area to make a decision. Visual information processing is a complex of technologies based on: grouping and generalization of initial data and comparison of the characteristics of these graphic images; application of computer graphics methods for generalization, analysis and presentation of information; application of an object-oriented approach for building models of graphic and non-graphic objects; the use of modern intelligent or semi-intelligent graphical interfaces. We can say that visual processing is based on the use of advanced computer graphics systems, which include a database of models (templates – objects) and a database of procedures (processing methods).

 

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