Geographic information systems (GIS)

Geographic information systems (GIS) capture, manage, manipulate, and present geographical data. GIS involves a combination of hardware, software, and collated data to analyze conditions, trends, and events in the natural environment. They may be used to map and track natural resource, seismological, volcanic, meteorological, and climatological conditions around the world. A GIS is an invaluable tool for the analysis of regional and global systems.

Basic Principles

Geographic information systems (GIS) are integrated devices used to map natural events, trends, and conditions. GIS employs a number of different and separate hardware and software tools, such as satellite and aerial sensors and cameras, along with specialized computer databases and other systems.

GIS software employs a geographic reference, such as a digitized map, to study a given region. Depending on the type and complexity of the scientific pursuit, the GIS then applies one or more layers, applying the compiled data to that map. The resulting image (or rendering) provides a composite of the area being studied according to the respective scientist’s research.

Three general areas make up an integrated GIS program. The first is a series of numerical algorithms, which enable researchers to assign data to values on the geographic reference. The second is a table of statistics. In GIS research, this table is frequently extensive, comprising a large volume of data. The third is optimization: In the application of GIS to a specific area of focus, the user or users must be able to modify the software appropriately to conform to the research.

GIS is utilized in a number of scientific disciplines and fields, including the social sciences (such as sociology, political science, and history), engineering, epidemiology, the natural sciences, and geoinformatics. For the purposes of earth science, GIS has a wide range of applications of value. Scientists using this technology can map changes in the earth’s topography, follow climate shifts, analyze water resources, and study the impact of volcanic eruptions.

GIS focuses on the collection of data from a specific geographical location. This information, when combined with data from other locations, can help scientists create a composite of a particular concept. For example, GIS is used in the long-term study of the melting of glaciers. It also can be used to map the destruction caused by a volcanic eruption or to monitor pollution in a given area.

History

GIS has its roots in cartography. Indeed, scientists maintain that GIS could not exist without knowledge of the way maps are (and have been) created. One of the earliest examples of GIS comes from the middle of the nineteenth century when British physician John Snow began investigating the spread of cholera in London.

Snow hypothesized that an outbreak in 1854 was caused by a bacterium in contaminated water. He drew a map of London and, using data from the hospitals in the area, plotted on the map the locations in which cholera deaths had occurred. His map revealed that most victims lived near a particular water pump. Upon his recommendation, that pump was shut down, leading to an end to the outbreak.

GIS development continued much in the same manner as it did in the mid-nineteenth century. Before the advent of computer technology, one of the more popular methods employed by scientists when studying natural events and trends in a geographic location was to use an existing map of a region. When analyzing data, scientists would simply lay a clear plastic sheet over the map, showing the points of interest. GIS continued to develop along these lines; even today, many GIS systems require the use of computer-aided design (CAD) software, a system that scans high-resolution hard copies of existing maps. The images derived from these scans are used as the basis for overlapping images suited for a given study.

As a computer-based system, GIS was largely developed for governments. However, by the start of the twenty-first century, the private market for GIS software and hardware had developed quickly. By 2020, the GIS Certification Institute estimated that more than 670,000 people were using GIS systems as part of their professional careers and the industry had grown into a $28 billion business.

Raster and Vector Data

Two types of reference data are utilized on a GIS rendering, in addition to a separate data table. The first of these reference data is a set of indicators known as vectors. Vector data appear in three general manifestations: polygon, line, and point.

On the image, a polygon (a multisided geometric shape) represents a city or other boundary (such as a body of water or forest region). A line, or arc, depicts linear features, such as streets, rivers, railways, and trails. The third form of vector is the point. This type of data identifies singular points of interest, such as buildings and bridges. Vectors simplify locations on a given rendering, reducing clutter on the image. The user can obtain an enhanced view with the vectors, which can show more detail. Adjacent structures or physical features may come into view with the zoom.

The second type of reference data in a GIS image is the raster. A raster focuses on surfaces rather than features. They are, in essence, high-resolution images (such as aerial and satellite photographs) comprised of a grid of pixels. Rasters appear in two forms: continuous and discrete. Continuous rasters vary consistently with no clear boundaries. Examples of this type of cell include surface temperature and geographical elevation. Discrete rasters, however, have boundaries with attached categories, classes, and descriptions. Some examples of discrete rasters are data for population density and political boundaries.

Advantages and disadvantages come with the use of rasters and vectors. Vectors, for example, use less of a computer system’s memory because of their relative simplicity and low volume of data. However, because of their simplicity, vectors can be easily adjusted for scale. Rasters, on the other hand, use a complex system of values, allowing for a number of different operations, including mathematical calculations. Then again, the high resolution and complexity of rasters require the user’s computer system to contain a significantly larger memory to perform any spatial analysis.

The ease with which vector data are managed in GIS analyses has made vector analysis a preferred choice among many researchers. Software developers are, as a result, introducing GIS programs that can convert reference data from raster to vector formats. Still, a large number of GIS programs have various raster-vector conversion programs, enabling the user to access and manipulate a range of maps and images.

Spatial Analysis

GIS accesses and analyzes spatial (or geographic) data. In spatial analysis, the data for each map layer are provided in an adjoining table. Each data point is assigned a value, which is typically performed through numerical algorithms and statistics. Analysis considers the relationships among each point. In many cases, these points lie within a larger feature (such as a building or geographic area). Spatial analysis also may require assessing the relationships among two or more points in different geographic locations.

The data provided on a given area may not automatically correspond to a predesigned map, or it may be anticipated that the map will change in light of certain conditions. For example, satellite-based thermal images may not delineate a mountain or a structure. Additionally, a scan of a shrinking rainforest may require multiple images and points of reference to demonstrate a chronological change. In such cases, it is important to generate an appropriate map. In these situations, GIS software typically calls upon modeling and forecasting programs to create a base image for spatial analysis.

GIS-generated spatial analysis helps scientists collate and utilize the attributes of a given reference point (or series thereof). Such data help researchers develop clear illustrations of a given geographic area in a far more comprehensive manner than that which is uncovered simply by flying over or driving through a target area.

For example, scientists in Israel conducted research on the availability of drinking water in the nearby Gaza Strip. The project entailed the acquisition of data on rainfall, population increases, and the number of reservoirs available in Gaza and the generation of a useful map to serve as the basis for the spatial analysis. Using GIS, this project created an analytical framework that identified the areas of highest consumption from groundwater reservoirs. The models produced by this GIS application also provided accurate short-term forecasts for groundwater usage in this area.

Mapping Topography

Until the mid-to-late twentieth century, scientists were limited in their ability to study the earth’s topography. Although aerial photographs and ground-based analysis prove effective in some areas, scientists were, until this period, unable to study a wide range of locations and trends in the natural environment.

One such location is the ocean floor. Although hidden from plain sight, the ocean floor contains fish habitats and provides indications of the impact of humanity on the natural environment. To better survey the suboceanic environment, scientists are increasingly calling upon GIS to map the ocean floor.

For example, scientists at Oregon State University utilized GIS to create a surficial geologic habitat map. This map is seen as critical for the region and its fishing industry, which has been in crisis because of concerns about depleted fish populations. Using a series of different mapping software that employs sonar data and density information, and seismic imaging and other databases and systems, researchers can effectively map the floor off the coast of Oregon with three-dimensional images and other relevant applications.

In another example, GIS technology was employed to study the bedrock of Oklahoma. Here, researchers used a digital elevation model to map the sandstone and shale that compose that state’s bedrock. Understanding the geology of this area is important for that state, with implications in its agricultural and civil engineering sectors.

Natural Resources

Applying GIS to the study of the Earth’s natural resources has been evolving since the late 1970s. However, this endeavor has seen increased success with the development of computer modeling and satellite-based technologies. In rural areas of North America and Pakistan, for example, GIS has proved effective in mapping forest resources. The use of such technology is particularly useful for studying the decline of forest cover from overdevelopment and unsustainable logging practices.

In an era in which sustainable development and protection of natural resources, such as drinking water and agriculture, are of increasing importance, GIS is a highly effective vehicle for analyzing trends and, ultimately, creating environmentally friendly policies. In developing countries and regions, this issue is particularly critical. For example, the area around Turkey’s Tuz Lake (the second-largest lake in Turkey and one of the largest salt lakes in the world) is considered an important region for agriculture and for many different forms of animal life.

Scientists began to develop a strategy for land use in the area, considering the area’s delicate ecological balance and such elements as soil and water quality, climate, and land suitability. Using GIS mapping, researchers created an overlapping series of maps of the region accounting for each of these ecological factors. The result of the study was a comprehensive land-use framework that outlined sustainable agricultural use, effective waste management, and the protection of the lake area’s wildlife.

Software

GIS involves integrated and open-source software technologies. Among these systems is CAD software.

CAD is used to design a high-resolution image that can be manipulated by zooming in and out, adding overlapping images, and viewing segments of an image from multiple angles. Although many CAD systems are built into appropriate hardware, a growing number of CAD software programs may be obtained independently, including through the Internet.

In addition to CAD, GIS requires the integration of spatial indexing software. This type of system enables spatial data to be stored, modified, and analyzed within the database. Spatial indexing software is used to collate statistics and data and assign them to an appropriate vector and raster. Spatial indexing and development software must be compatible with the CAD program in use, as the resulting reference data (vectors and rasters) will be overlain on the main composite image. Like CAD, this software is now available on the Internet. Furthermore, because GIS-based studies commonly feature a large amount of data, it is important that the integrated system in use includes a high-volume database application.

In addition to web-based software, another innovation useful to GIS researchers is mobile GIS applications. Because the memory storage of smartphones, tablets, and other mobile systems is ever-increasing, researchers can now access and utilize GIS software from their mobile devices.

Implications and Future Prospects

GIS has evolved so extensively that it is being applied across a broad spectrum of scientific disciplines. Social scientists use GIS to map and analyze demographics and residential populations. Civil engineers employ GIS to assess the viability of constructing roads, bridges, and other structures. Public health professionals use it not only to track diseases but also to analyze potential health threats and benefits for populations.

The evolution of GIS also has been aided by the parallel evolution of sensory hardware. In terms of earth science, advances in thermal imaging, radar, seismography, and other technologies add a number of additional resources to spatial analysis. Furthermore, the accessibility of the global positioning system and other satellite-borne hardware systems now enable scientists to study a geographic location with ever-greater detail. Many of these advanced systems can “see” through weather, foliage, and even topographical features, all of which were previously considered obstacles to spatial analysis.

As with other scientific disciplines, it is likely that GIS will continue to have relevance for researchers in the field of earth science. The private sector market for GIS continues to grow because of its applicability to so many fields. Government and nongovernmental research on such issues as sustainable development, climate change, and natural resource management will only continue to drive this interest. Further, government agencies like NASA have embraced GIS systems to enable a system of open data where science is shared with the greater community.

Principal Terms

computer-aided design: software that generates high-resolution images that may be manipulated by the user

open source: software in which the source code may be accessed by the public and modified without the application of copyright laws

optimization: aspect of a software program that enables the user to modify it to conform to the user’s needs

raster: cell-based, high-resolution image that assigns data on surface conditions

rendering: manipulated GIS image that shows data overlain on the original map image

spatial: pertaining to space and geography

vector: spatial point used in GIS to indicate surface features such as structures, bodies of water, and roadways

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