1. What is GIS?
GIS is a set of computer hardware, geographic data and software for collecting, processing, storing, modeling, analyzing and displaying all types of spatially referenced information.
GIS is a medium that links geographic information (where things are) with descriptive information (what they are). Unlike conventional paper maps (even scanned ones), where “what you see is what you get,” GIS puts at your disposal multiple layers of diverse general geographic and thematic information.
2. How is information stored in GIS?
All the original information - where the points are located, how long the roads are or the area of the lake - is stored in separate layers in digital form on a computer. And all this geographic data is sorted into layers, with each layer representing a different type of feature (topic). One of these topics may contain all the roads in a certain territory, another - lakes, and a third - all cities and other settlements in the same territory.
http:// www.dataplus.ru/Arcrev/Number_43/1_Geograf.html
3. GIS can be considered in three types:
GIS can be considered in three Types:
Database type: GIS is a unique type of database about our world—a geographic database. This is the "Information System for Geography". GIS is based on a structured database that describes the world in geographical terms, from the point of view of the spatial location of its objects and phenomena.
Card type: A GIS is a collection of smart maps and other graphical views that show features and their relationships on the earth's surface. Maps can be generated and used as a “window into a database” to support queries, analysis and editing of information. These actions are called geovisualization.
Model type: GIS is a set of tools for transforming information. They allow you to create new geographic data sets from existing ones by applying special analytical functions to them - geoprocessing tools. In other words, by combining data and applying some rules, you can create a model that helps you answer your questions.
http://www.dataplus.ru/Arcrev/Number_43/1_Geograf.html
4. What can you do with GIS?
Perform spatial queries and analysis
search databases and perform spatial queries
identify areas suitable for the required activities; identify relationships between various parameters (for example, soils, climate and crop yields); identify locations of power outages
http://moslesproekt.roslesinforg.ru/activity/023gil-inform
5. Where are GIS used?
Realtors use GIS to search, for example, all the houses in a certain area
GIS are used for graphical construction of maps and obtaining information about individual objects
Engineering communications company
GIS helps, for example, in solving such problems as providing a variety of information at the request of planning authorities, resolving territorial conflicts, choosing optimal (from different points of view and according to different criteria) locations for placing objects, etc.
http://gis-laris.narod.ru/primen_gis.htm
6. What is GPS?
GPS - satellite navigation system , providing distance, time and location measurements.
http://ru.wikipedia.org/wiki/GPS
7. Who uses GPS?
GPS has a number of applications on land, at sea and in the air. Basically, they can be used wherever a satellite signal can be received, with the exception of inside buildings, in mines and caves, underground and under water.
http://www.1yachtua.com/Encycl/Elctrn/IspGPS.html
8. What is a GPS receiver (GPS navigator)?
GPS receiver- a radio receiving device for determining the geographic coordinates of the current location of the receiver antenna, based on data on the time delays in the arrival of radio signals emitted by satellites of the NAVSTAR group. In Russia, with the development of the GLONASS system, serial production of GLONASS receivers began by a number of design bureaus and organizations.
http://ru.wikipedia.org/wiki/GPS-%D0%BF%D1%80%D0%B8%D1%91%D0%BC%D0%BD%D0%B8%D0%BA
9. How cards are used in GPS receivers?
The presence of the card significantly improves the user characteristics of the receiver. Receivers with maps show the position not only of the receiver itself, but also of objects around it.
All electronic GPS maps can be divided into two main types - vector and raster.
http://wiki.risk.ru/index.php/GPS-%D0%BF%D1%80%D0%B8%D0%B5%D0%BC%D0%BD%D0%B8%D0%BA
Geocaching(geocaching from Greekγεο- - Earth and English cache- cache) - a tourist game using satellite navigation systems, which consists in finding caches, hidden by other participants in the game.
http://ru.wikipedia.org/wiki/%D0%93%D0%B5%D0%BE%D0%BA%D0%B5%D1%88%D0%B8%D0%BD%D0%B3
11. Who plays geocaching?
It can be played with family, company or alone
Geocaching is actively used as corporate entertainment. Employees of the supply company hide caches, instruct participants, and provide them with equipment and GPS navigators.
http://ru.wikipedia.org/wiki/%C3%E5%EE%EA%FD%F8%E8%ED%E3
12. What is Google Earth?
A project by Google, within which satellite photographs of the entire earth's surface were posted on the Internet. Photos of some regions have unprecedented high resolution.
In many cases, the Russian version of Google Earth is called Google Earth, for example, in the main menu or on the official website.
http://ru.wikipedia.org/wiki/GoogleEarth
13. Google Earth Features?
- Viewing satellite images - easy navigation, seamless connection of satellite images and instant display with gradual drawing of details;
- Construction of perspective (relief) images with overlay of satellite images;
- Drawing your points, lines and polygons and exporting them to a special file (in Google format) for sharing with other GE users;
- Overlaying your images (for example, logos, your own maps, etc.) and their approximate alignment with the underlying surface;
- Measuring distances;
- Flight of an area at a given altitude and speed.
http://gis-lab.info/qa/google-earth.html
2 GIS Saratov
http://saratov.2gis.ru/
Practical work "2 GIS Saratov"
Exercise 1: Using the Catalog tool (in the upper left corner of the program), look at the catalog of organizations in the city of Saratov.
Task 2: Use the Search system. Enter the address (optional), district. The program will automatically indicate the required address.
Task 3: To build directions by public transport or car between any points on the map, use the block "How can I get to?" on the tab Search.
Geographic information system (GIS, Also geographic information system) are electronic spatially oriented images (maps, diagrams, plans, etc.) and databases integrated into a single information environment. GIS includes the capabilities of database management systems (DBMS), raster and vector graphics editors and analytical tools and is used in cartography, geology, meteorology, land management, ecology, municipal government, transport, economics, defense and many other areas.
Based on territorial coverage, there are global GIS, subcontinental GIS, national GIS, often with state status, regional GIS, subregional GIS and local GIS.
How GIS works
A GIS stores information about the real world as a set of thematic layers that are aggregated based on geographic location. This simple but very flexible approach has proven its value in solving a variety of real-world problems: tracking the movement of vehicles and materials, detailed mapping of real-life conditions and planned activities, and modeling global atmospheric circulation.
Any geographic information contains information about spatial location, whether it is a reference to geographic or other coordinates, or references to an address, postal code, electoral district or census district, land or forest identifier, road name or milepost on a highway, etc. .
layered representation of geographic information in GIS
Key Benefits of GIS
- User-friendly display of spatial data
Mapping spatial data, including in three dimensions, is most convenient for perception, which simplifies the construction of queries and their subsequent analysis. - data integration within the organization
Geo Information Systems combine data accumulated in various departments of the company or even in different areas of activity of organizations in an entire region. Collective use of accumulated data and their integration into a single information array provides significant competitive advantages and increases the efficiency of operation of geographic information systems. - making informed decisions
Automating the process of analyzing and generating reports on any phenomena related to spatial data helps speed up and increase the efficiency of the decision-making procedure. - convenient tool for creating maps
Geographic information systems optimize the process of deciphering data from space and aerial surveys and use already created terrain plans, diagrams, and drawings. GIS significantly save time resources by automating the process of working with maps and creating three-dimensional terrain models.
Industry uses of GIS
The capabilities of geographic information systems can be used in a wide variety of areas of activity. Here are just some examples of using GIS:
administrative-territorial management
- urban planning and site design;
- maintaining cadastres of engineering communications, land, urban planning, green spaces;
- forecast of emergency situations of technogenic and environmental nature;
- management of traffic flows and urban transport routes;
- building environmental monitoring networks;
- engineering-geological zoning of the city.
telecommunications
- trunk and cellular communications, traditional networks;
- strategic planning of telecommunication networks;
- selection of the optimal location of antennas, repeaters, etc.;
- determination of cable laying routes;
- network status monitoring;
- operational dispatch control.
engineering Communication
- assessment of needs for water supply and sewerage networks;
- modeling the consequences of natural disasters for utility systems;
- design of engineering networks;
- monitoring the condition of utility networks and preventing emergency situations.
transport
- road, rail, water, pipeline, air transport;
- management of transport infrastructure and its development;
- fleet management and logistics;
- traffic management, route optimization and cargo flow analysis.
oil and gas complex
- geological exploration and field survey work;
- monitoring of technological operating conditions of oil and gas pipelines;
- design of main pipelines;
- modeling and analysis of the consequences of emergency situations.
law enforcement agencies
- first responders, military, police, fire services;
- planning rescue operations and security measures;
- modeling of emergency situations;
- strategic and tactical planning of military operations;
- navigation of first responders and other law enforcement agencies.
ecology
- assessment and monitoring of the state of the natural environment;
- modeling of environmental disasters and analysis of their consequences;
- planning of environmental measures.
forestry
- strategic forestry management;
- logging management, forest access planning and road design;
- maintaining forest cadastres.
Agriculture
- planning of agricultural land cultivation;
- accounting of landowners and arable land;
- optimization of transportation of agricultural products and mineral fertilizers.
GIS Examples
Google Earth
A project by Google, within which satellite photographs of the entire earth's surface were posted on the Internet. Photos of some regions have unprecedented high resolution.
Unlike other similar services that display satellite images in a regular browser (for example, Google Maps), this service uses a special Google Earth client program that is downloaded to the user’s computer. Although this approach requires downloading and installing the program, it later provides additional capabilities that are difficult to implement using the web interface. This program was originally released by Keyhole and then purchased by Google, which made the program publicly available. There are also paid Google versions Earth Plus and Google Earth Pro, featuring support for GPS navigation, presentation tools and increased print resolution.
Possibilities:
- Google Earth automatically downloads the images and other data the user needs from the Internet, stores them in the computer's memory and on the hard drive for further use. The downloaded data is saved on disk, and upon subsequent launches of the program, only new data is downloaded, which allows you to significantly save traffic.
- To visualize the image, a three-dimensional model of the entire globe (taking into account altitude above sea level) is used, which is displayed on the screen using DirectX or OpenGL interfaces. It is in the three-dimensionality of the landscapes of the Earth's surface that the main difference between the Google Earth program and its predecessor Google Maps lies. The user can easily move to any point on the planet by controlling the position of the “virtual camera”.
- Almost the entire land surface is covered with images obtained from DigitalGlobe, which have a resolution of 15 m per pixel. There are certain areas of the surface (usually covering the capitals and some large cities of most countries of the world) that have more detailed resolution. For example, Moscow was filmed with a resolution of 0.6 m/pc, and many US cities were filmed with a resolution of 0.15 m/pc. The landscape data has a resolution of about 100 m.
- There is also a huge amount of additional data that can be connected at the user's request. For example, names of settlements, reservoirs, airports, roads, railways, and other information. In addition, for many cities there is more detailed information - street names, shops, gas stations, hotels, etc. There is a geodata layer (synchronized via the Internet with the corresponding database), which displays (with spatial reference) links to articles from Wikipedia. In Russia you can see the names of the streets of all cities in the central regions.
- Users can create their own tags and overlay their images on top of satellite images (this can be maps, or more detailed images obtained from other sources). These tags can be shared with other users of the program through the Google Earth Community forum. Tags posted to this forum become visible to all Google Earth users after about a month.
- The program has a “3D Buildings” layer, with three-dimensional models added by developers or users themselves through the 3D Warehouse service. In Russian cities you can find models of some significant architectural monuments.
- There is also a simplified Java version of the program for cell phones.
- There is a function for measuring distances.
- Version 4.2 introduced Google Sky technology, which allows you to view the starry sky.
- In version 5.0, the ability to view a three-dimensional map of the bottom of seas and oceans was introduced.
GeoMedia technology is a new generation GIS architecture that allows you to work directly without import/export simultaneously with a variety of spatial data in various formats. This is achieved by using special data access components - Intergraph GeoMedia Data Server.
Allows you to visualize and analyze spatial information (search, filtering by condition, dynamic visualization by condition or from changes in information in the database, buffer zones, statistics, proximity analysis, topological analysis (such as “is object A located inside object B”, etc.) and many others), preparing maps for printing. For end users (not GIS designers and administrators), running template queries in a customized work session environment. Directly (without converting or damaging the data at this point) connects to the following information sources (servers and files in appropriate formats): ArcGIS, MapInfo, MGE, GeoMedia (storage on the Microsoft Access platform, Microsoft SQL Server, Oracle Server), universal databases data from Oracle Server, IBM DB2 and Microsoft SQL Server, vector maps or graphics in MicroStation (Bentley Systems), AutoCAD (Autodesk) and others formats, raster data (with and without georeferencing) such as aerospace images and scanned paper maps in formats TIFF, JPEG, CIT, RLE, etc., WMS web servers, spreadsheets, ODBC tabular data sources and even ASCII texts (as a full-fledged storage, but, of course, formatted). Not suitable for editing and/or creating data (digital maps).
NASA World Wind
A fully 3D interactive virtual globe created by NASA. Uses NASA satellite imagery and USGS aerial photography to build 3D models of the planet. Initially, the program contains low-resolution maps. As you zoom in on the area in question on the map, high-resolution images are downloaded from NASA servers.
The program allows you to select the scale, direction and angle of view, visible layers, and search by geographical names. It is possible to display the names of geographical objects and political boundaries.
The zoom function is implemented in World Wind by changing the height from which the camera looks at the surface. From a great height, the image looks flat, but from a height of several tens of kilometers in the mountains, the perspective effect is clearly visible, and the smooth scrolling of the image creates the impression of flying over the real terrain.
In addition to the image of the Earth, the program also shows the surface of the Moon. The images were taken from the Clementine satellite, which was launched in 1994 and has taken about 1.8 million images since then. NASA World Wind allows you to observe the Moon at almost any point on it by adjusting the zoom of the image. The image clearly shows the relief of the natural satellite, mountains, craters and crevices. Some images are so detailed that it makes it possible to customize the view of the lunar surface from twenty meters.
gvSIG
Free geographic information system with open source. The first working version appeared at the end of 2006 and was distributed via the Internet. It is a geographic information management tool with an intuitive interface that works perfectly with both raster and vector formats. gvSIG is being developed with a government grant from Spain.
The program supports all the necessary GIS functions:
- Working with layers, thanks to which you can display only the objects that are necessary at the moment;
- Map zoom functions;
- Support for saving the necessary map views;
- Automatic calculations of the distance between objects and areas of areas;
- Placing active objects on the map;
- Create professional geographic maps with the necessary elements that can later be printed.
ArcGIS
A family of software products from the American company ESRI, one of the leaders in the global market of geographic information systems. ArcGIS is built on the basis of COM, .NET, Java, XML, SOAP technologies. The newest version is ArcGIS 10.
ArcGIS allows you to visualize (present in the form of a digital map) large volumes of geographically referenced statistical information. Maps of all scales are created and edited in the environment: from land plans to a world map.
Also, ArcGIS has built-in wide tools for analyzing spatial information.
ArcGis is used in a variety of areas:
A geographic information system designed for geomodeling, managing spatial vector and raster data, processing satellite images, creating printed cartographic products and much more.
The package works with all modern DBMSs, supports topology, three-dimensional visualization, allows vectorization using various techniques and has many other features inherent in expensive commercial products like ESRI ArcGIS or MapInfo. Due to these qualities, GRASS is widely used in commercial and scientific projects (for example, GRASS is actively used by NASA).
It should be noted that GRASS GIS is one of the oldest geographic information systems. Its development was initiated by the U.S. Army Construction Engineering Research laboratory in 1982. In 1995, the GRASS source code was published under the GPL license.
The main feature of GRASS is its modular structure, which allows the formation of a GIS from individual functional units, optimized for the needs of the end user.
Main groups of modules:
- visualization;
- interaction with DBMS (storage of spatial and attribute information);
- image processing (processing satellite images, creating composite images, geometric and chromatic correction);
- print management;
- working with raster maps (shade models, scaling);
- working with vector maps (spatial analysis operations, attribute queries);
- and etc.
To work with map projections and coordinate systems, GRASS uses the proj library, which allows you to “understand” more than 30 thousand different types of them. Import and export are carried out through the GDAL library. Shapefile, MapInfo TAB, PostGIS, DXF, GeoTIFF, IMG and any other formats are supported.
Sources
- http://tinyurl.com/2ulhlrh
- http://ru.wikipedia.org/wiki/ Today, GeoMedia users have access to components for all major industrial formats for storing digital map data: ArcInfo, ArcView, ASCII, AutoCAD, FRAMME, GeoMedia, GML, MapInfo, MGE, MicroStation, Oracle Spatial, etc., including raster, tabular and multimedia data . However, users can develop their own GeoMedia Data Server based on a custom format template. Intergraph GeoMedia Data Server components allow you to view and simultaneously analyze data from an arbitrary number of sources, stored in different formats, coordinate systems, and with varying accuracy, on one map.This approach allows you to maintain investments in existing GIS solutions, while simultaneously moving to a new level of integration of enterprise information resources.
The GeoMedia product family includes two core product lines - desktop and server - plus additional application modules.
GeoMedia is the prototype of the first version of international standards in the field of GIS, developed by the Open GIS Consortium and, at the same time, is the first implementation of these standards.
Geographic information systems and technologies
Geographic information system (GIS) is a multifunctional information system designed for collecting, processing, modeling and analyzing spatial data, their display and use in solving calculation problems, preparing and making decisions. The main purpose of GIS is to generate knowledge about the Earth, individual territories, terrain, as well as timely delivery of necessary and sufficient spatial data to users in order to achieve the greatest efficiency of their work.
Geoinformation technologies (GIT) are information technologies for processing geographically organized information.
The main feature of GIS, which determines its advantages in comparison with other AIS, is the presence of a geoinformation basis, i.e. digital maps (DC), providing the necessary information about the earth's surface. At the same time, the Central Committee must ensure:
precise binding, systematization, selection and integration of all incoming and stored information (single address space);
complexity and clarity of information for decision making;
the possibility of dynamic modeling of processes and phenomena;
the ability to automatically solve problems related to the analysis of territory features;
the ability to quickly analyze the situation in emergency cases.
The history of the development of GIT dates back to the work of R. Tomlison on the creation of the Canadian GIS (CGIS), carried out in 1963-1971.
In a broad sense, GIT is data sets and analytical tools for working with coordinated information. GIT is not information technology in geography, but information technology for processing geographically organized information.
The essence of the GIT is manifested in its ability to connect some descriptive (attributive) information (primarily alphanumeric and other graphic, sound and video information) with cartographic (graphic) objects. Typically, alphanumeric information is organized in the form of tables in a relational database. In the simplest case, each graphical object (and usually point, linear and area objects are distinguished) is assigned a table row - a record in the database. The use of such a connection, in fact, opens up such rich functionality for GIT. These capabilities naturally vary from system to system, but there is a basic set of functions typically found in any GIT implementation, such as the ability to answer questions like “what is this?” indicating the object on the map and “where is it located?” highlighting on the map objects selected according to some condition in the database. The basic ones can also include the answer to the question “what’s nearby?” and its various modifications. Historically, the first and most universal use of GIT is information retrieval and reference systems.
Thus, GIT can be considered as a kind of extension of DB technology for coordinated information. But even in this sense, it represents a new way of integrating and structuring information. This is due to the fact that in the real world most of the information relates to objects for which their spatial position, shape and relative position play an important role, and therefore GIT in many applications significantly expands the capabilities of conventional DBMSs, since GIT are more convenient and intuitive to use and provide the DL with their own “cartographic interface” for organizing a query to the database along with means for generating a “graphical” report. And finally, GIT adds completely new functionality to conventional DBMSs - the use of spatial relationships between objects.
GIT allows you to perform operations on sets of cartographic objects similar to ordinary relational ones (JOIN, UNION, INTERSECTION). The operations of this group are called overlay, since they use, in different ways, the spatial overlay of one set of objects on another. In fact, overlay operations have great analytical potential, and for many areas of application, GIT are the main ones, providing solutions to applied problems (land use, comprehensive assessment of territories, and others).
GIT offers a completely new way for the development of cartography. First of all, the main disadvantages of conventional cards are overcome: static data and the limited capacity of “paper” as an information carrier. In recent decades, not only complex specialized maps such as environmental maps, but also a number of ordinary paper maps become “unreadable” due to information overload. GIT solves this problem by managing the visualization of information. It becomes possible to display on the screen or on a hard copy only those objects or sets of them that the user needs at the moment. That is, in fact, a transition is taking place from complex comprehensive maps to a series of interconnected private maps. This ensures better structure of information, which allows it to be used effectively (manipulation, data analysis, etc.). It is obvious that there is a tendency for the role of GIT to increase in the process of activating information resources, because Huge amounts of cartographic information can be effectively converted into active machine-readable form only with the help of GIT. In addition, in GIT the map becomes a truly dynamic object.
The latter is due to the following new GIT capabilities:
changeability of scale;
transformation of map projections:
varying the object composition of the map;
“poll” through a map in real time of numerous databases containing changeable information;
varying symbology, that is, the way objects are displayed (color, line type, etc.), including defining symbology through the values of attribute characteristics of objects, which allows you to synchronize visualization with changes in the database.
There is now a widespread understanding that GIT is not a class or type of software systems, but the underlying technology (umbrella technology) for many computer applications (methods and programs) that work with spatial information.
Since DCMs are data sets of complex structure, it is advisable to present them in various formats. The DCM format refers to a specially introduced system of classification and coding of terrain data. The efficiency of solving functional problems (FP) in military control systems largely depends on the adopted format of the digital computer. So, for example, in the case of representing the terrain with contour lines, calculating the terrain profile takes thousands of times longer than when representing the terrain in the form of a height matrix.
One of the most important and most common types of information needs in geoinformation is the construction of an image of a map section on the AWS screen (map visualization). But the means of displaying digital computers on the workstation screen, along with the above requirements for access means, must meet a number of specific requirements determined by the need for human perception of information. Essentially, these are the following ergonomic requirements, which should be considered in conjunction with others:
according to the “readability” of the situation (i.e. have enough high performance speed and reliability of human perception of information about the operational situation against the background of the map);
by the “readability” of the map (i.e., have sufficiently high characteristics of speed and reliability of human perception of the cartographic information itself);
according to the “comfort” of perception (i.e., the form of data display should not cause excessive stress on a person when perceiving information and irritation of his senses in order to ensure the required duration of maintaining his performance).
The Federal Law requires various data about the terrain for its decision. According to the authors, the entire set of these tasks, according to the nature of the use of digital computers, can be divided into four main classes:
tasks that require the output of a map image to input-output devices of automation equipment and use it as a background for displaying the operational situation (OCF);
tasks using information about the nature and profiles of terrain (OHPM);
tasks using information about the road network (RDN);
tasks that use information about the location of an object within the territory of the state, zone of responsibility or neutral territory (WMD).
OKF tasks are all tasks that reflect the operational situation on the ground in the process of dialogue with the user. These tasks can display “on top of the map” information about groupings of friendly and enemy troops, zones of radioactive, chemical, biological contamination, complete destruction, fires, floods, directions and boundaries of action, concentration areas, etc. A common feature of the OKF tasks is the use of TsKM lies in the need to quickly display the map image on the workstation screen at various scales.
The tasks of the OKPM include the task of choosing the location for the deployment of radio relay stations (RRS), tropospheric stations (TRS), radar stations (PJIC), electronic reconnaissance equipment, electronic warfare, etc. The tasks of assessing the protective properties of the terrain in the areas of deployment of control points (CP) and communication centers (CS), planning fire impact, etc. also belong to the OKPM class. A special feature of OHPM tasks is the need to determine with high speed the characteristics of the terrain in the vicinity of a point with arbitrary coordinates.
The tasks of the RDS include, in particular, the tasks of determining the route and planning the order of movement of military units, optimal planning of transportation of supplies or mail, and some others. These tasks use DCM data on the road network, which must be presented in a special form - in the form of a graph in which all intersecting roads have a common vertex at the intersections.
WMD tasks use in the central digital computer data on state (land and sea) and other borders, specified in a special form - in the form of closed contours.
Based on the type of information needs, many federal laws can be classified into several different classes. In particular, the task of determining the optimal deployment area for RRS may have properties of the OKPM and RDS classes, and in the process of solving for organizing a dialogue with the user - properties of the OKF class.
Due to the deep interpenetration of GIS and other information technologies It is advisable to consider the relationship between GIT and other technologies.
First of all, these are graphic technologies of computer-aided design systems (CAD), vector graphic editors, and on the other hand, relational DBMS technologies. Most implementations of modern GIT are basically an integration of these two types of information technologies. The next type of related information technology is image processing technology of raster graphic editors. Some GIT implementations are based on a raster representation of graphic data. Therefore, many modern general purpose GIS integrate the capabilities of both vector and raster representation. In turn, a number of image processing technologies designed to work with aerial and space survey data are very closely related to GIT, and sometimes partially perform their functions. But usually they are complementary to GIT and have special tools for interacting with them (ERDAS LiveLink to ARC/INFO)
Closely related to GIT are cartographic (geodetic) technologies used in processing data from field geodetic surveys and constructing maps based on them (when constructing maps from aerial photographs using photogrammetric techniques and when working with a digital terrain model). There is also a tendency towards integration here, because The vast majority of modern GIS include coordinate geometry tools (COGO), which allow direct use of field geodetic observation data, including directly from digitally recorded instruments or from satellite global positioning system (GPS) receivers. Photogrammetric packages are usually oriented towards collaboration with GIS and in some cases are included in GIS as modules.
The essence of the GIT is manifested in its ability to connect some descriptive (attributive) information (primarily alphanumeric and other graphic, sound and video information) with cartographic (graphic) objects. Typically, alphanumeric information is organized in the form of tables in a relational database. In the simplest case, each graphical object (point, linear or area) is associated with a table row - a record in the database. The use of such a connection provides rich functionality of the GIT. These capabilities naturally vary from system to system, but there is a basic set of functions typically found in any GIT implementation, such as the ability to answer questions like “what is this?” indicating the object on the map and “where is it located?” highlighting on the map objects selected according to some condition in the database. The basic ones can also include the answer to the question “what’s nearby?” and its various modifications. Historically, the first and most universal use of GIT is information retrieval and reference systems.
Thus, GIT can be considered as a kind of extension of DB technology for coordinated information. But even in this sense, it represents a new way of integrating and structuring information. This is due to the fact that in the real world most of the information relates to objects for which their spatial position, shape and relative position play an important role. Consequently, GIT in many applications significantly expands the capabilities of conventional DBMSs.
GIT, like any other technology, is focused on solving a certain range of problems. Since the areas of application of GIS are quite wide (military affairs, cartography, geography, urban planning, organization of transport dispatch services, etc.), due to the specifics of the problems solved in each of them, and the features associated with a specific class of problems being solved and with requirements for input and output data, accuracy, technical means, etc., it is quite problematic to talk about any single GIS technology.
At the same time, any GIT includes a number of operations that can be considered as basic. They differ in specific implementations only in details, for example, a software service for scanning and post-scan processing, the capabilities of geometric transformation of the source image depending on the initial requirements and quality of the material, etc.
Since the above model is generalized, it is natural that it either does not contain individual blocks characteristic of any specific technology, or, on the contrary, contains those blocks that in some cases may be missing.
Based on the results of the analysis of the generalized GIS technology model, the following basic GIT operations can be identified:
- editorial and preparatory work, i.e. collection, analysis and preparation of source information (cartographic data, aerial photographs, remote sensing data, ground observation results, statistical information, etc.) for automated processing;
- design of geodetic and mathematical bases of maps;
- map design;
- construction of a digital thematic map project;
- converting raw data into digital form;
- development of a layout of thematic content of the map;
- determination of methods for automated construction of thematic content;
- formation of a digital general geographical basis for the created map;
- creation of a digital thematic map in accordance with the developed project;
- obtaining output cartographic products.
To enter initial information, raster scanning devices, digitizers, and grayscale scanners of aerial photo negatives are used. The resulting digital data sets are fed into a complex of technical means for processing raster and vector data, built on the basis of workstations and personal professional computers. All stages of design, transformation of source information and creation of a digital thematic map are carried out on the same tool base.
The generated digital cartographic model enters the complex of technical means for generating output cartographic products, which includes plotters, printers, specialized output devices on photo media, etc.
Raw and processed digital data is stored in an archival storage subsystem, currently based on tape drives or optical disks.
The areas of application of GIT are currently extremely diverse.
First of all, these are various cadastres, distributed management systems and infrastructure. Specialized applications have been developed here, for example, for systems: electrical networks of an energy company, cable network of a telephone or television company, complex pipeline facilities of a large chemical plant, land registry operating real estate, as well as applications such as complex systems serving many components of the infrastructure of a city or territories
and capable of solving complex management and planning problems. Specific goals and objectives in such systems are very diverse: from inventory and accounting tasks, public reference systems to taxation, urban planning and planning tasks, planning new transport routes and transportation optimization, distribution of a network of resources and services (warehouses, shops, ambulance stations assistance, car rental points).
Another developed area of application of GIT is the accounting, study and use of natural resources, including environmental protection. Here you can also find both complex systems and specialized ones: for forestry, water management, study and protection of wild fauna and flora, etc. This area of application is directly related to the use of GIT in geology, both in scientific and practical problems. These are not only information support tasks, but also, for example, the task of forecasting mineral deposits, monitoring the environmental consequences of developments, etc. In geological applications, as well as in environmental ones, the role of applications that require complex programming or integration of GIT with specific processing and modeling systems is great. Applications in the field of oil and gas stand out especially in this regard. Here, at the search and exploration stage, seismic data and very specific and developed software for their processing and analysis are widely used. There is a great need for comprehensive solutions that link geological and other problems themselves, which cannot be solved without the involvement of universal GIS.
Separately, it is necessary to highlight purely transport tasks. Among them: planning new transport routes and optimizing the transportation process with the ability to take into account the distribution of resources and the changing transport situation (repairs, traffic jams, customs barriers). Navigation systems, especially those based on satellite navigation systems using digital cartography, are expected to be particularly promising in strategic terms.
A characteristic feature of the implementation of GIT at present is the integration of systems and databases into national, international and global information structures. Global projects include, for example, GDPP - “Global Database Project”, developed within the framework of the International Geosphere-Biosphere Program. At the national level, there are GIS in the USA, Canada, France, Sweden, Finland and other countries. In Russia, regional GIS are currently being developed, in particular, for maintaining the land cadastre and municipal administration, as well as departmental GIS, for example, in the Ministry of Internal Affairs.
An analysis of the current experience in the use of GIT shows that the main form of application of GIT is GIS of various purposes, complexity, composition and capabilities.
Modern GIS represent a new type of integrated systems, which, on the one hand, include methods for processing data from existing automated systems, and on the other hand, they have specificity in the organization and processing of data
Since GIS handles complex information processing (from collection to storage, updating and delivery), they can be viewed from the following different perspectives:
- GIS as a management system - designed to provide decision support based on the use of cartographic data;
- GIS as an automated information system - combines a number of technologies from well-known information systems (CAD and others);
- GIS as a geosystem - includes technologies of photometry, cartography;
- GIS as a system using a database is characterized by a wide range of data collected using different methods and technologies;
- GIS as a modeling system, a system for providing information, is a development of documentary circulation systems, multimedia systems, etc.
GIS with developed analytical capabilities are close to systems of statistical analysis and data processing, and in some cases they are integrated into unified systems, for example:
implantation of the powerful statistical package S-PLUS into the modern GIS ARC/INFO;
adding some spatial statistics and cartographic visualization capabilities to popular statistical packages (SYSTATfor Windows);
development of our own GIS within the SAS package - a leader among numerical information processing systems.
The most developed GIS (usually with strong support for raster models), with good programming tools, are widely used for modeling natural and man-made processes, including the spread of pollution, forest fires, etc. Some conventional DBMSs operating in graphical environments such as MS Windows also include simple cartographic visualization tools.
The presence of a wide range of development trends in different areas of information technology, whose interests converge in the field of GIT, as well as the emergence of universal packages of wide application, has led to the fact that the boundaries of the definition of GIT are becoming less clear. Therefore, the concept of a full-featured GIS (full GIS) has now emerged.
A modern full-featured GIS is a multifunctional information system designed for collecting, processing, modeling and analyzing spatial data, displaying it and using it in solving calculation problems, preparing and making decisions. The main purpose of a fully functional GIS is to generate knowledge about the Earth, individual territories, terrain, as well as timely delivery of necessary and sufficient spatial data to users in order to achieve the greatest efficiency of their work.
A fully functional GIS should provide:
- two-way communication between cartographic objects and tabular database records;
- control of visualization of objects, providing choice of composition and form of display;
- working with point, linear and area objects;
- inputting cards from a digitizer or scanner and editing them;
- supporting topological relationships between objects and using them to check the geometric correctness of the map, incl. closedness of area objects, connectivity, adjacency, etc.;
- support for various map projections;
- geometric measurements on the map of length, perimeter, area, etc.; construction of buffer zones around objects and implementation of other overlay operations;
- creating your own symbols, including new types of markers, line types, hatch types, etc.; creating additional map design elements, in particular signatures, frames, legends;
- output of high-quality hard copies of maps; solving transport and other problems on graphs, for example, determining the shortest path, etc.;
- working with topographic surfaces.
In addition to fully functional general-purpose GIS, there are specialized ones, which often have unclear boundaries with specialized packages that are not GIS in this sense. For example, GIS, focused on communication planning tasks, transport and navigation tasks, engineering survey tasks and structure design.
Non-specialized GIS of a lower level than full-featured general-purpose systems are usually called “desktop mapping systems” (desktop GIS), sometimes even separating this class of systems from the GIS itself. Their distinctive feature is, first of all, limited analytical capabilities (for example, there are no overlay operations for area objects) and poor capabilities for entering and editing the cartographic basis. A typical example of such a system is the GIS Maplnfo, in which, due to its lower complexity, it is easier to learn and use and is more accessible to the mass user.
To date, the number of GIS packages offered on the market amounts to several thousand. However, most of these are specialized systems. There are several dozen real full-featured general-purpose GIS packages on the market. Mostly software GIS is developed by specialized companies, only in some cases these are products of large companies for which GIS is not the main product (IBM, Intergraph, Computervision, Westinghouse Electric Corp., McDonnel Douglas, Siemens Nixdorf). In terms of the number of known packages and the number of installations, PCs (MS DOS, MS Windows) and UNIX workstations predominate.
It should be noted that currently, full-featured general-purpose GISs are mainly targeted at workstations running the UNIX operating system. On PCs, as a rule, systems with reduced capabilities operate. This is partly determined by the specifics of PC users, for many of whom a simple GIS is needed only as an addition to regular office software. But the main reason is the demands that a powerful GIS places on computer hardware.
Topological vector data structures are complex in nature, and the processes of their use require intensive calculations, much more than working with conventional vector graphics, including in terms of floating point operations. Serious applications often require working with long integers and double precision real numbers. Working with GIS requires high-resolution displays and a fast graphics adapter or accelerator, and the palette requirements are stricter than in CAD. They are rather similar to the requirements for professional printing publishing systems. Particularly high demands on rendering speed are imposed by the typical GIS (and less typical CAD) task of filling a large number of closed polygons of complex shape with hatching.
Serious projects using GIS require working with large volumes of data, from hundreds of megabytes to several tens of gigabytes. Particularly high demands on the volume of disk and main memory, as well as on computer speed, are placed on GIS with image processing in the form of raster structures, for example, in tasks of geometric correction of aerial photographs, modeling of natural processes and when working with the relief of the earth's surface. One high-resolution color aerial photograph in standard format, if converted to digital form without loss of “accuracy” (24 bit, 1200 dpi), takes up about 200 MB. In many tasks of a regional nature, it is necessary to use a combined and geometrically corrected mosaic of many such images, especially since it is considered advisable to use a raster background from such a mosaic of aerial or satellite images (digital orthophoto) as a base layer for vector maps, i.e. photographs are “imprinted” onto the card image. The same remark is also true for working with aerospace images, which, as a rule, must be processed in various ways in order to selectively highlight various information on them (various types of filtering operations, contrast transformations, operations using the fast Fourier transform, classification algorithms, discriminant, cluster and factor analysis, as well as the method of principal components). Therefore, instead of storing dozens of processing versions, which would require up to hundreds of GB per 1 frame, it is more rational
perform them on demand. Modern specialized workstations cope with this task, but for a PC it is still difficult. Sometimes a single frame operation on a PC takes several minutes. When it is necessary to simulate complex natural processes, in particular the spread of pollution, forest fires, or to use aerospace survey data, the use of a specialized workstation is inevitable.
It should be noted that the rate of accumulation of volumes of aerospace (especially space) data is still at the same pace or even faster than the rate of growth in the computing power of PCs and workstations. Indeed, at least 800-1000 MB of satellite images are collected every month over every area of the Earth the size of a large city. And even if we take into account that half of them, due to cloud conditions, are unsuitable for use in GIT applications, this still amounts to a huge flow. And one more note: the resolution of remote information collection systems is constantly growing, and increasing the geometric resolution on the ground from 20 to 10 m increases the volume of data by 4 times. So every 2-4 years, a computer system must increase its productivity several times in order to keep up with the pace of development of information collection devices. From this it is clear that for a long time specialized workstations will remain the technical basis of powerful, fully functional GIS with analytical functions.
Another point that necessitates the need to pay significant attention to WVZY workstations is the fact that today the main packages of the most “serious” GIS have not yet been transferred to PCs.
The main areas of using a PC when working with GIS are currently:
- using PCs as terminals together with workstations for working with large GIS (ARC/INFO);
- using PCs as stations for inputting and modifying digital terrain maps from a digitizer or scanner (PC ARC!INFO, ArcCAD);
- using a PC for GIT projects with a small amount of simultaneously active information (PC ARC/INFO, ArcCAD, ArcView);
- using a PC for educational purposes, to get acquainted with the GIT methodology;
- using a PC at the initial stages of large projects, when the volume of the database has not yet grown, full functionality is not required for large volumes, and it is still necessary to prove the usefulness of using GIT and the need to invest serious funds.
Since modern GIS are, as a rule, complex software and information systems designed specifically for use in specific areas of information activity or for solving specialized problems, they include:
- operating system;
- application software core;
- modules for thematic data processing;
- interactive user interface.
Thematic data processing modules include:
- data input/output software;
- application software for analysis of vector and raster information;
- DBMS;
- pattern recognition software;
- map projection selection software;
- image conversion software;
- cartographic generalization software;
- symbol generation software, etc.
Designed for collecting, storing, analyzing, and graphically visualizing spatial data.
Definition 1
In the language of geography, GIS are tools that make it possible to search, analyze, edit digital maps and the necessary additional information about any objects.
GIS is widely used in cartography, geology, meteorology, land management, ecology, municipal government, transport, economics, defense and other fields.
According to the coverage of the territory, GIS can be:
- Global;
- Subcontinental;
- National;
- Regional;
- Subregional;
- Local or local.
Spatial data is those that describe the location of objects in space, and GIS makes it possible to add, delete, update, query, view, and analyze this data. Spatial data is presented in the form of basic formats - vector graphics and rasters.
Definition 2
Raster image is a two-dimensional array of points, where each point is represented by its own color.
To design the “background” of a digital map, raster graphics are usually used, and vector geometry is displayed on top of it. For example, on Yandex maps you can see a huge number of rasters. A huge amount of spatial information can be displayed with small amounts of memory, and this, without a doubt, great advantage raster images on digital maps.
Negative point, perhaps, is that as the display scale increases, the quality of the image on the raster decreases significantly. It is quite clear that different scales will use rasters of different territorial coverage and resolution. They will replace each other if the picture needs to be enlarged or reduced.
Vector graphics. It is nothing more than geometry represented as sets of coordinates. The image itself is not stored; it is generated on the fly under the visualization system and, regardless of the scale, has a high image quality.
Types of vector spatial data:
- Point geometry. Most often this is a point on the map of a certain color. In some cases, GIS replace this point with an arrow, icon, raster image, vector symbol;
- Linear geometry. The use of this type is advisable when it is important to show the length and area. Such objects, as a rule, are roads, rivers, territorial boundaries, etc.;
- Areal geometry. This type will be used when absolutely everything is important.
Using GIS you can answer the following questions:
- What is located in such and such a place;
- Where exactly is it located;
- What has changed since some time;
- What spatial structures exist;
- What happens, for example, if you add a new road, i.e. modeling.
Problems that GIS solves
A general purpose geographic information system performs primarily five data tasks—input, manipulation, management, query and analysis, and visualization.
Input task. To enter data into a GIS, it must be converted into a suitable digital format. The conversion process is called digitization and can be automated using scanning technology.
Manipulation task may arise when the existing data of a particular project needs to be further modified in accordance with the requirements of the system. For example, geographic information has different scales—street lines at one scale, county boundaries at another, and residential properties at a third scale. It is clear that it is much more convenient to work with information when it is on the same scale and the same map projection. In this regard, GIS technologies provide different ways to manipulate spatial data.
Control task is easily visible when geographic information of small projects is stored as regular files. If the volume of information and the number of users increase, then it is much more efficient to use a database management system (DBMS) to store, structure and manage data. The most convenient is a relational structure that stores data in tabular form. This approach is flexible and widely used.
Query and analysis. GIS makes it possible to get answers not only to simple questions, for example, who is the owner of this land plot? but also complex ones that require additional analysis. Queries are created by clicking a mouse on a specific object or through advanced analytical tools. To analyze the proximity of objects in relation to each other, a buffering process is applied.
Visualization. The result in the form of a map or graph for many types of spatial operations is final. The most effective and informative way to store, present, and transmit geographic information has always been a map. If maps have been created over centuries, today, with the help of GIS, new tools have emerged that expand and develop cartography. Visualization makes it possible to quickly and easily supplement maps with reporting documents, graphs, tables, diagrams, and photographs.
Prospects for the development of GIS technologies
Note 1
During the implementation of the program to provide the Russian population with information, GIS technologies must be modernized and improved. For this purpose, the Ministry of Communications and Information of the Russian Federation made an order to the AYAXI company in $2002$ for the development of the design and system of Internet sites for the Federal Target Program “Electronic Russia for $2002$-$2010$.” In accordance with the provisions of the Okinawa Charter of the Global Information Society, the President of Russia in $2000 signed the “Concept for the formation and development of a unified information space of Russia and state information resources.”
Development occurs in two stages:
- First stage associated with the creation of an electronic representation of the Federal Target Program “Electronic Russia” on the Internet and filling sites with socially significant information.
- Second phase associated with the reorganization of sites into an interactive portal.
Portal principles:
- All administrative barriers are eliminated when introducing information and communication technologies that meet the interests of state security;
- Mandatory openness of concepts for discussion of program goals and objectives by stakeholders;
- Impossibility of duplicating work that is implemented within other programs;
- Maximum savings in budgets of all levels and reduced financial burden;
- Published information materials should form public opinion in support of activities carried out within the framework of the Federal Target Program "Electronic Russia";
- Information materials must reflect the official position of executive authorities.
Modern computer society has one very important trend, which is associated with the transition to a network environment for transmitting information. Small and medium-sized companies connect their computers into a network. There are both advantages and new challenges.
the main problem is to share access to data and protect information from unauthorized access. During the development of the personal computer, certain capabilities were laid down to separate access to data, and blocking was carried out at the file level. When a file is modified by an operator, everyone else can only view it and nothing more. In developed countries, for example, all land cadastre systems for the population are accessible. Within Russia, a unified information network of real estate objects is also being formed. This does not contradict the information law and is an important point for public control over the real estate market. Today, the priority for GIS is targeting the mass non-professional user.
GIS is a modern geographic information system mobile systems, which have the ability to display their location on the map. This important property is based on the use of two technologies: geoinformation and If a mobile device has a built-in GPS receiver, then with the help of such a device it is possible to determine its location and, therefore, the exact coordinates of the GIS itself. Unfortunately, geographic information technologies and systems in the Russian-language scientific literature are represented by a small number of publications, as a result of which there is almost no information about the algorithms underlying their functionality.
GIS classification
The division of geographic information systems occurs on a territorial basis:
- Global GIS has been used to prevent man-made and natural disasters since 1997. Thanks to this data, it is possible in a relatively short time to predict the scale of the disaster, draw up a plan for eliminating the consequences, assess the damage caused and human losses, and organize humanitarian actions.
- Regional geographic information system developed at the municipal level. It allows local authorities to predict the development of a certain region. This system reflects almost all important areas, such as investment, property, navigation and information, legal, etc. It is also worth noting that thanks to the use of these technologies, it has become possible to act as a guarantor of the life safety of the entire population. The regional geographic information system is currently being used quite effectively, helping to attract investment and the rapid growth of the region's economy.
Each of the above groups has certain subtypes:
- Global GIS includes national and subcontinental systems, usually with state status.
- In the regional - local, subregional, local.
Information about these information systems can be found in special sections networks called geoportals. They are posted in the public domain for review without any restrictions.
Principle of operation
Geographic information systems work on the principle of compiling and developing an algorithm. It is this that allows you to display the movement of an object on a GIS map, including the movement of a mobile device within the local system. To depict a given point on a terrain drawing, you need to know at least two coordinates - X and Y. When displaying the movement of an object on a map, you will need to determine the sequence of coordinates (Xk and Yk). Their indicators must correspond to different points in time of the local GIS system. This is the basis for determining the location of the object.
This sequence of coordinates can be extracted from a standard NMEA file of a GPS receiver that has performed real movement on the ground. Thus, the algorithm considered here is based on the use of NMEA file data with the coordinates of an object’s trajectory over a certain territory. The necessary data can also be obtained by modeling the movement process based on computer experiments.
GIS Algorithms
Geographic information systems are built on initial data that is taken to develop an algorithm. As a rule, this is a set of coordinates (Xk and Yk) corresponding to a certain trajectory of the object in the form of an NMEA file and a GIS digital map of a selected area. The task is to develop an algorithm that displays the movement of a point object. In the course of this work, three algorithms underlying the solution of the problem were analyzed.
- The first GIS algorithm is the analysis of NMEA file data in order to extract from it a sequence of coordinates (Xk and Yk),
- The second algorithm is used to calculate the path angle of the object, while the parameter is counted from the direction to the east.
- The third algorithm is for determining the course of an object relative to the cardinal points.
Generalized algorithm: general concept
The generalized algorithm for displaying the movement of a point object on a GIS map includes the three previously mentioned algorithms:
- NMEA data analysis;
- calculating the path angle of an object;
- determining the course of an object relative to countries around the globe.
Geographic information systems with a generalized algorithm are equipped with a main control element - a timer. Its standard purpose is that it allows the program to generate events at certain intervals. Using such an object, you can set the required period for executing a set of procedures or functions. For example, to repeatedly count a time interval of one second, you need to set the following timer properties:
- Timer.Interval = 1000;
- Timer.Enabled = True.
As a result, every second the procedure for reading the X, Y coordinates of the object from the NMEA file will be launched, as a result of which this point with the obtained coordinates is displayed on the GIS map.
How the timer works
The use of geographic information systems occurs as follows:
- Three points are marked on the digital map (symbol - 1, 2, 3), which correspond to the trajectory of the object at different times tk2, tk1, tk. They must be connected by a solid line.
- Turning on and off the timer that controls the display of the movement of an object on the map is carried out using buttons pressed by the user. Their meaning and a certain combination can be studied according to the diagram.
NMEA file
Let us briefly describe the composition of the NMEA GIS file. This is a document written in ASCII format. Essentially, it is a protocol for exchanging information between a GPS receiver and other devices, such as a PC or PDA. Each NMEA message begins with a $ sign, followed by a two-character device designator (for a GPS receiver, GP), and ends with the sequence \r\n, a carriage return and line feed character. The accuracy of the information in the notification depends on the type of message. All information is contained on one line, with fields separated by commas.
In order to understand how geographic information systems work, it is enough to study the widely used $GPRMC message, which contains a minimal but basic set of data: the location of an object, its speed and time.
Let's look at a specific example to see what information is encoded in it:
- date of determination of object coordinates - January 7, 2015;
- universal time UTC coordinates determination - 10h 54m 52s;
- object coordinates - 55°22.4271" N and 36°44.1610" E.
We emphasize that the coordinates of the object are presented in degrees and minutes, and the latter indicator is given with an accuracy of four decimal places (or a dot as a separator of the integer and fractional parts of a real number in the USA format). In the future, you will need the fact that in the NMEA file the latitude of the object’s location is in the position after the third comma, and the longitude is after the fifth. At the end of the message, it is transmitted after the symbol "*" in the form of two hexadecimal digits - 6C.
Geographic information systems: examples of compiling an algorithm
Let's consider an algorithm for analyzing an NMEA file in order to extract a set of coordinates (X and Yk) corresponding to the object. It is composed of several successive steps.
Determining the Y coordinate of an object
NMEA Data Analysis Algorithm
Step 2. Find the position of the third comma in the line (q).
Step 3. Find the position of the fourth comma in the line (r).
Step 4. Find, starting at position q, the decimal point symbol (t).
Step 5. Extract one character from the string located at position (r+1).
Step 6. If this symbol is equal to W, then the NorthernHemisphere variable gets the value 1, otherwise -1.
Step 7. Extract (r-+2) characters of the string starting at position (t-2).
Step 8. Extract (t-q-3) characters of the string starting at position (q+1).
Step 9. Convert the strings to real numbers and calculate the Y coordinate of the object in radian measure.
Determining the X coordinate of an object
Step 10. Find the position of the fifth comma in the line (n).
Step 11. Find the position of the sixth comma in line (m).
Step 12. Find, starting at position n, the decimal point symbol (p).
Step 13. Extract one character from the string located at position (m+1).
Step 14. If this character is "E", then the EasternHemisphere variable gets the value 1, otherwise -1.
Step 15. Extract (m-p+2) characters of the string starting at position (p-2).
Step 16. Extract (p-n+2) characters of the string, starting at position (n+1).
Step 17. Convert the strings to real numbers and calculate the X coordinate of the object in radian measure.
Step 18. If the NMEA file is not fully read, then go to step 1, otherwise go to step 19.
Step 19. Finish the algorithm.
Steps 6 and 16 of this algorithm use the variables NorthernHemisphere and EasternHemisphere to numerically encode the location of an object on Earth. In the northern (southern) hemisphere, the NorthernHemisphere variable takes the value 1 (-1), respectively, similarly in the eastern EasternHemisphere - 1 (-1).
Application of GIS
The use of geographic information systems is widespread in many areas:
- geology and cartography;
- trade and services;
- cadastre;
- economics and management;
- defense;
- engineering;
- education, etc.