GIS Applications – Geography – UGC NET – Notes

• Geographic Information Systems (GIS) are computer-based systems designed to capture, store, manage, analyze, and display geographically referenced data. GIS integrates spatial data, attribute data, and analytical tools to support understanding of spatial relationships, patterns, and processes.
• GIS applications are used across disciplines including geography, urban planning, environmental management, public health, transportation, defense, agriculture, and disaster management.
• Among the most significant applications of GIS are thematic cartography and spatial decision support systems, which transform raw spatial data into meaningful information for analysis and decision-making.

Concept and Evolution of GIS Applications

• The application of GIS emerged from developments in cartography, remote sensing, computer science, and spatial analysis during the mid-twentieth century. Early GIS applications focused on automated mapping and land-use analysis.
• Advancements in database management systems, geospatial modeling, satellite imagery, and computing power expanded GIS capabilities from simple map production to complex spatial analysis and decision support. Modern GIS applications involve real-time data processing, three-dimensional visualization, and integration with global positioning systems and remote sensing technologies.

Thematic Maps/Cartography

• A thematic map is a map that focuses on a particular theme or special topic. These maps are different from the six aforementioned general reference maps because they do not just show features like rivers, cities, political subdivisions, elevation, and highways. If these items appear on a thematic map, they are background information and are used as reference points to enhance the map’s theme.
• This Canadian map, for example, which shows changes in population between 2011 and 2016, is a good example of a thematic map. The city of Vancouver is broken down into regions based on the Canadian Census. Changes in the population are represented by a range of colors ranging from green (growth) to red (loss) based on the degree of change.
• A thematic map is a type of map specifically designed to “show a particular theme connected with a specific geographic area.
• Unlike reference maps, which tell us where something is, thematic maps tell us how something is.
• There are a number of visualization techniques and thematic map types that have different applications depending on the type of data that you are exploring and the type of spatial analysis that you are looking to do.
• The methodology and the type of map that you want to create may be different, for example, if you are exploring global shipping data or voter propensity, or environmental disaster impact.
• All thematic maps use maps with coastlines, city locations and political boundaries as their base maps. The map’s specific theme is then layered onto this base map via different mapping programs and technologies like a geographic information system (GIS).
• A thematic map is a specialized map made to visualize a particular subject or theme about a geographic area. Thematic maps can portray physical, social, political, cultural, economic, sociological, or any other aspects of a city, state, region, nation, continent, or the entire globe.
• A thematic map is designed to serve a special purpose or to illustrate a particular subject, in contrast to a general map, on which a variety of phenomena appear together, such as landforms, lines of transportation, settlements, and political boundaries.
• This is in direct contrast to a reference map or Topographic map, which are designed to show the location of visible features of the landscape with minimal interpretation and intended to be used for a wide variety of purposes.
• Thematic maps also portray basic features such as coastlines, boundaries and places, but they are only used as a point of locational reference for the phenomenon being mapped. Thematic maps also emphasize spatial variation of one or a number of geographic distributions. These distributions may be physical phenomena such as climate or human characteristics such as population density and health issues. Barbara Petchenik described the difference as “in place, about space.”
• While general reference maps show where something is in space, thematic maps tell a story about that place based on spatial patterns. Thematic maps are sometimes referred to as graphic essays because they display spatial variations and interrelationships of geographical distributions that can be interpreted.

History of Thematic Maps

• Thematic maps did not develop as a map type until the mid-17th Century because accurate base maps were not present prior to this time. Once they became accurate enough to display coastlines, cities and other boundaries correctly, the first thematic maps were created.
• In 1686 for example, Edmond Halley, an astronomer from England, developed a star chart. In that same year, he published the first meteorological chart using base maps as his reference in an article he published about trade winds. In 1701 , Halley also published the first chart to show lines of magnetic variation- a thematic map that later became useful in navigation. Halley’s maps were largely used for navigation and the study of the physical environment.
• In 1854, John Snow, a doctor from London created the first thematic map used for problem analysis when he mapped cholera’s spread throughout the city. He began with a base map of London’s neighborhoods that included all streets and water pump locations. He then mapped the locations where people died from cholera on that base map and was able to find that the deaths clustered around one pump and determined that the water coming from the pump was the cause of cholera.
• In addition to these maps, the first map of Paris showing population density was developed by a French engineer named Louis-Leger Vauthier. It used isolines (a line connecting points of equal value) to show population distribution throughout the city and was believed to be the first use of isolines to display a theme that did not have to do with physical geography.