Table of Contents
What is GIS?
GIS stands for Geographic Information system. GIS has so many functions in our world today, it should be viewed as a process rather than as merely software or hardware. To see GIS as merely a software or hardware system is to miss the crucial role it can play in a comprehensive decision-making process. GIS does not refer to a homogeneous entity, nor one machine or a single practice but to a collection of practices, software and hardware with the ability to collect, store, display, analyse and print information about the Earths surface (or any other scale of geographical data). Each such system is able to capture, store, check, integrate, analyse and display spatially referenced data about aspects of the earth.
GIS Definition by Different Authors
- The U.S. Geological Survey in 1992, defined Geographic Information System (GIS) as a computer system (s) capable of assembling, storing, manipulating and displaying geographically reference information. Such systems, in fact, have power, utility ad importance far beyond this definition, both within and beyond the field of geography. Their most valuable potential capability which sets them apart from computer mapping systems, is the ability to perform spatial analyses to address research and application questions.
- GIS is defined as the computer system build to capture, store, manipulate, analyze, manage and display all kinds of spatial or geographical data.
- GIS is a powerful set of tools for collecting, storing, retrieving at will, transforming and displaying spatial data from the real world this definition was given by Burrough in 1987.
- GIS is a computer assisted system for capture, storage, retrieval, analysis and display of spatial data, within a particular organization (Clarke, 1986).
- GIS is an information technology which stores, analyzes and display both spatial and non-spatial data (Parker, 1988).
- GIS is defined as a decision support system involving the integration of spatial referenced data in a problem solving environment (Cowen, 1988)
- GIS is seen as a system with advanced geo-modeling capabilities (Koshkariov, Tikunov and Trofimov, 1989).
- GIS is an organized collection of computer Hardware, Software, Data and Analyst to effectively capture, store, manipulate, analyze and retrieve all types of spatial and non-spatial information. It is ageographic information system. Like any information system, a GIS is an organized accumulation of data and procedures that help people make decisions about what to do with things.
However, Geographical Information is information about where something is or what is at a certain location. For example, we may collect data from a forest on where some of the few remaining spotted eagles live which is geographical information. What trees grow in the areas inhabited by these eagles is also a geographical information, because it has a spatial component. Spatial data are any data that have a location that can be geocoded.
GIS is uniquely integrative. Where spatial data are available, GIS can offer a range of functionality. Whereas other technologies might be used only to analyse aerial photographs and satellite images, to create statistical models or to draft maps, these capabilities are all offered together within a comprehensive GIS.
Importance/Uses of GIS
- GIS has different uses in decision-making process. Municipalities, for instance, view GIS as the software that allows planners to identify residential, industrial and commercial zones and store tax information. It maps the exact location and survey coordinates of each taxable property, and provides answers to queries such as How many properties would be affected by the addition of an extra lane to Highway 1 between 170th and 194th Streets?
- Population health researchers, on the other hand, may use GIS to define the boundaries of communities that enjoy varying health outcomes. In this instance, GIS is not a piece of software, but a scientific approach to the problem.
- GIS can be used to perform an extensive variety of spatial operations and analyses on properly coded data. At the most elementary levels are computations of distances, areas, centroids, gradients, and volumes.
- More complex operations that add spatial referencing to a basic calculation are also possible, for example, going beyond questions about the total length of a citys sewer lines to questions about the total length of sewer lines in a given area in a particular city and what proportion of this length is more than 50 years old.
- GIS is used to facilitate a variety of management and planning decisions in both public and private sectors. For instance, in Wake County, North Carolina, potentials sites for schools, libraries and other facilities have been determined by identifying adequately sized parcels of vacant land and providing information about utilities, topography and demographic characteristics of the local population.
- GIS has a growing role in international policy and planning associated with human welfare.
- Many businesses have taken advantage of the rapidly growing commercial aspects of GIS to offer hardware, software, data, consulting and other marketable aspects, today, GIS is a multibillion dollar business and still growing at a very high rate.
- Finally, GISs are also capable of more complicated operations such as:
- Calculating new spatial datasets based on attributes of existing data, for instance, calculating slopes from elevation
- Comparing two or more spatial datasets based on user-specified criteria, for example identifying toxic waste sites that are situated on permeable soil
- Delimiting areas that possess certain characteristics defined by the user for examples, delimiting locations of commercially zoned land within 2miles of an interstate highway and
- Modelling the possible outcomes of alternative processes and policies for example, determining the impact of flooding along the Mississippi River given the presence or absence of leaves.
GIS allows the combination of geographical data sets (or layers) and the creation of new geospatial data to which one can apply standard spatial analysis tools. Comprehensive GIS require a means of: (i)data input, from maps, aerial photos, satellites, surveys and other sources (remote sensing);(ii) data storage, retrieval, and query; (iii) data transformation, analysis and modeling, including spatial statistics; and also as (iv) data reporting, such as maps, reports and plans.
With GIS, digital cartography recognizes two principal types of data, raster and vector data.
Raster Data: a method of storing, representing or displaying spatial form. It consists of using cells data (not necessarily square) arranged in a regular grid pattern in which each unit (pixel or cell) within the grid is assigned and identifying value based on its characteristics. Examples of raster data include landcover data acquired from space with a multispectral scanner, digital elevation models (DEMs) consisting of surface elevations sampled for a grid with rows and columns spaced 30m apart, and images scanned from historical topographic maps and nautical charts. The spatial quality of a raster data set is described by the spatial resolution of the sensor or scanner.
Vector data: One method of storing, representing or displaying spatial data in digital form; it consists of using coordinate pairs (X,Y) to represent locations on the earth features on the earth can take a form of single points, lines, arcs or close lines ( polygons). It is a system of recording features based on the interaction between arcs and nodes represented by points, lines and polygons. Example of vector data are counties or census tracts. In addition, attribute data describe the type of feature, its name or identifying number, and specialized characteristics such as the population of a census tract or the width and left- and right-hand address ranges of a street segment.
History of GIS Development
The term GIS did not come to play until the early 1960s when Canadian Geographic Information System (CGIS) was developed. Between this period, and now, the technology used to construct a GIS and the functions of it have undergone considerable change. The history of GIS development can be grouped into three:
- The formative years
- The years of maturing technology and
- The age of Geographic Information Infrastructure.
The Formative Years (1960- 1970)
The origin of GIS is strongly dependent on researches and developments in electronic data processing which dates back to 1940s and 1950s. This led to the successful implementation of computer added graphic data processing at the Massachusetts Institute of technology (MIT) in 1955 and database management system (DBMS) by General Electric in !965. These breakthroughs allowed for bulk processing of large amounts of complex data electronically and quickened government agents to invest in the computer system that could handle Geographic Data. The result is the development of the CGIS which was set up to address the needs of land and resources information management of the federal government of Canada. This system has been formally recognized as the First GIS.
The Maturing Technology Years (1980-MID 1990)
The major milestone in the development of GIS concepts and techniques is the breakthrough in the concept of topology as applied to spatial data. Within geographic data structures, topology refers to the spatial relationship of adjacency, connectivity and containment amongst topographic features. Based on this concept, geographical data can be stored in simple structures that are capable of representing their attributes (i.e. what they are), location (where they are and their relationship (how they spatially relate with one another). During this period, more sophistications ware introduced by GIS vendors into the software packages, this allowed for more user control and interaction. There was also a shift in GIS functionality aiming to satisfy a specific need or objective to one another that met the demand of corporate business goals and information requirement.
Age of Geographic Information Infrastructure (MID 1990- Date)
The concept of emerged in the early 1990s when the United States Government Proposed a National Information Infrastructure (NII) with objectives to provide all US citizens access to information affecting their lives that pertains to Government, Health care, Education, and Community Development . Thus, GIS was made part of this information that would be provided. In 1994, President Clinton ordered the implementation of the National Spatial Data infrastructure (NSDI). This was defined as technology, policies, standards and human resources to acquire, process, share, distribute and improve the utilization of geospatial data.