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Geographic Information Systems: an introduction: Home

Research guide introducing GIS

Geographic Information Systems (GIS) are now commonplace in our lives, but do we know how to use them effectively? Follow this guide to learn more about the theory behind GIS applications and choose the correct program for your assignment or project.

Introduction

What GIS (Geographic Information System) is:

GIS consists of computer hardware, software, digital data and people. 

A GIS is a computer-based database for capturing, storing, analyzing, and managing data and associated attributes that are spatially referenced to the earth

What GIS can do:

A common feature of GIS is that they allow you to associate information (non-geographical data) with places (geographical data). In fact, the GIS Application can store many pieces of information which are associated with each place –– something that paper maps are not very good at

Some Terminology:

A digital map is comprised of Vector and Raster data.

Vector data:

Vector data is stored as a series of X, Y coordinate pairs inside the computer’s memory. Vector data is used to represent points, lines and areas.

Raster data:

Raster data are stored as a grid of values. [...] One important difference between raster and vector data is that if you zoom in too much on a raster image, it will start to appear ‘blocky’

Example:

Images of the surface have adequate detail up to a certain point. After that they become pixilated. Look at the two images of the city of Nur-Sultan and notice how the vector data remain the same, despite the greater zoom:

Map projections & Coordinate reference systems

Map projections try to portray the surface of the earth or a portion of the earth on a flat piece of paper or computer screen. A coordinate reference system (CRS) then defines, with the help of coordinates, how the two-dimensional, projected map in your GIS is related to real places on the earth.

Three common types of map projections are portrayed above:

  • cylindrical
  • conical
  • planar

One of the most popular is the Mercator projection. When you overlay an image to your digital map, it will "bend" according to the map projection you use in your system!

CRS are consisted of lines of Longitude and lines of Latitude, and their intersections give the exact position of a place on Earth.

Sources:

Website: A gentle introduction to GIS. Accessed: 30.10.2017

Abresch, J. (Ed.). (2008). Integrating Geographic Information Systems into Library Services: A Guide for Academic Libraries: A Guide for Academic Libraries. IGI Global.

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