The concept of GIS is not geographically new. In the original sense, geographers use such systems for many years, but "footsteps" - without the use of a computer. For example, drawing on paus paper and overlapping such pauses is a classic example. Such an example is the cholera epidemic in London in 1854. Dr. John Snow found the position of the infectious disease site by drawing deaths. He found that the concentration of some 500 cases was within a few hundred meters around a public water pump at Broad Street, Soho. Dr Snou managed to prove the following: when the pump handle was removed, the new cases were not diagnosed in that street. He proved that the pump was the source of these cases of infection and that the source of the infection was infected with water using a simple data analysis.
Is a branch of statistics that deals with field data, spatial data with a continuous index. It provides methods to model spatial correlation, and predict values at arbitrary locations (interpolation).part 1.
Geocoding is interpolating spatial locations (X,Y coordinates) from street addresses or any other spatially referenced data such as ZIP Codes, parcel lots and address locations.Part 2.
Reverse geocoding is the process of returning an estimated street address number as it relates to a given coordinate. For example, a user can click on a road centerline theme (thus providing a coordinate) and have information returned that reflects the estimated house number.Part 3.
Cartography is the design and production of maps, or visual representations of spatial data.Part 4.
Traditional maps are abstractions of the real world, a sampling of important elements portrayed on a sheet of paper with symbols to represent physical objects. People who use maps must interpret these symbols. Topographic maps show the shape of land surface with contour lines or with shaded relief.Part 5.
The implementation of a GIS is often driven by jurisdictional (city,country,...), purpose, or application requirements. Generally, a GIS implementation may be custom-designed for an organization. Hence, a GIS deployment developed for an application, jurisdiction, enterprise, or purpose may not be necessarily interoperable or compatible with a GIS that has been developed for some other application, jurisdiction, enterprise, or purpose.Part 6.
Vectors models are points, lines and polygons. Vector data is not made up of a grid of pixels. Instead, vector graphics are comprised of vertices and paths. The three basic symbol types for vector data are points, lines and polygons (areas). Because cartographers use these symbols to represent real-world features in maps, they often have to decide based on the level of detail in the map.
In the Geographic Information System, common purpose is to make decisions in managing some spatial activities, so that GIS can be defined as an IS for the purpose of collecting, processing, managing, analyzing, displaying and maintaining spatially oriented information.
Metadata are a set of attributes needed to describe a resource-data data. For example, metadata is used in library books to describe books, so the library catalog contains a brief description of each book (author name, title, brief description, place on the shelf, ...). There are two ways to store data and metadata:
Generally in digital format, digital data can be divided into vector and raster formats. The raster consists of a rectangular network of the same dimensions (pixels), where each rectangle has its value. The vector format uses simple geometric shapes such as a point, a line segment, and a polygon. The biggest advantage over raster format is that it takes up less memory space.
As an example, a circle in a two-dimensional space can be indicated. The definition of a circle by raster format is almost impossible (there would be an infinite number of pixels), while only a few data is sufficient for the definition of a circle in a vector format: radius and coordinates of the center.
Spatial data has certain characteristics that can be described by terms: form, location and relation to other spatial data (or geometry, position and topology). It is also important to model real-world data (such as roads or buildings) in terms of geographic representation.
For example, the path can be displayed by a line, and the building may be a polygon on the map. These properties (line, polygon) are actually models of real phenomena of the real world. Sometimes these models are called objects or entities. Another important aspect of spatial data is that they often contain attribute information. This means that the description of the occurrence (eg times) is kept in some form. The description may be a name or type of road (A, B, motorway), and the object would be a line segment.
The second example can be a trigonometric, which can be represented by a geometric shape of a point, and the attribute can be a height. The lakes could be represented by a geometric form of a polygon, with the attribute name. Most commonly, the same objects are grouped into layers, so that all trigonometers can be grouped into one layer, all the lakes in the second layer, all the paths in the third layer, and so on.
After collecting and adjusting geographic data to the system, it is necessary to preserve them in the geographic information system in charge of storing geographic data - a database. The data is stored in the database in an organized way (which is one of the advantages of information systems in general). Spatial databases should be used in spatial data.
Today, spatial data is collected in a particular coordinate system and visualized in a specific cartographic projection. Accose data is collected in one system, and the information system uses another coordinate system, the data needs to be adjusted through the conversion process.
Based on the previous text, it can be concluded that the software used in GIS can be divided into:
Often there are software packages that include all three features.
It primarily works with a shapefile format, or files are stored in that format. Shapefile is a set of at least three files with SHP, SXH and DBF extensions, and is currently the most used vector format in GIS developed due to interoperability by ESRI. Shapefile consists of geometric shapes (dot, line, or polygon), and corresponding tables. This table contains attributes of geometric shapes.
Of course, Qgis allows you to view other vector formats. In addition, it also provides an overview of various raster formats.
All data is organized by layers and each file is either in vector or raster format as one layer. When adding layers, they are arranged one above the other, but it is possible to change their layout, as well as the display properties (depending on the type of layer, ie, whether it is a raster or a vector). It is possible to record the current state (layer layout and their properties) in a file called the project, and has an extension of .qgs. Of course, for each layer and project, an appropriate projection is defined.
Vector layers contain objects that are of the same type ie. points, or lines, or polygons, and corresponding attributes. These layers can be edited (add / modify / delete objects or operations that can be performed depending on the type of objects the layer contains, ie whether objects, lines, or polygons are objects).
The tools are divided into several groups:
Attribute Tools - Allows you to select objects, change attributes, identify objects, and so on.