GIS has become somewhat mandatory. Our day-to-day myriad activities of life cannot go on without the helping hands of GIS.
Developed recently for the purpose of using and studying geographic information, geography underpins GIS and is the key to understanding it. It expresses and describes the locations of objects and features relating to the distribution and patterns of physical and human features that exist on the Earth’s surface.
Before the advancement of modern GIS, analysis procedures would have been manually undertaken using transparent overlays or run through very slow and incompetent machines with far less power than today’s machines. GIS in the past mainly meant the information obtained from maps.
The indispensable advantage of modern GIS is that all the functionality for working with manifold sets of geographic data are assembled and automated within one piece of software with improved efficiency and speed.
The input, storage and display of geographical information are now realized in a computer and hence the features and themes can be manipulated, combined and analyzed to generate new information.
Different GIS software packages are available with different functionality and interfaces. ESRI is the world’s most popular GIS software package.
Common examples of GIS
Geographic information is as wide and varied from socio-economic or demographic data to physical and environmental data, treated as separate l ‘themes’ of similar types of information. Eg: Physical features or phenomena such as rivers, roads, forests, earthquakes, volcanoes, erosion, floods, vegetation etc. and Human features or phenomena such as population, migration, electoral territories, poverty, religion, health etc.
One such theme could relate to all the ‘rivers’ in a country. The physical features can include flooding and pollution. The location element is the postcode.
One of the main sources of ‘human’ geographic information is the Census. It records a large number of variables about every person in the a country including employment, housing and health. The geography element of it is the location of where people live.
Essentially, geographic information states WHAT is WHERE which needs to record these two elements somehow. Data can be captured from aerial photography, satellite images, field samples, land surveying, population censuses, global positioning systems (GPS) and government administrative records among others.
For combining geographic information themes, geography or location is used as the common denominator or the link. It has the potential to generate new information on patterns and relationships between multiple sets of geographic information that would otherwise be missed, and to aid in answering more complex questions or decision-making.
A typical example is Jon Snow’s investigation of Cholera in Victorian London in 1854. He identified the locations of incidences of Cholera against the location of water pumps, and noticed its gathering pattern around the Broad Street water pump. He identified the contaminated source and created the beginning of modern epidemiology. A map of just the water pumps or incidences of Cholera alone would have been of little value.
Again take the example of flood risk maps where the combined geographic information on the locations of properties and the locations of flood zones can help to identify properties at risk of flooding. This combined information is of huge value to environmental groups and insurance companies providing new information that would not be detectable otherwise.
Modern GIS has several advantages over the old techniques of map-making and information gathering. Some of modern GIS are:
1.Can cover large study areas (the whole world if necessary)
2.Deal with larger amounts of data
3.Can easily select any sub-study area
4.Can cope with frequent and infinite edits and changes
5.More powerful and resistant to damage
6.Quicker and more efficient
7.Less person, time and money
The Census is the most familiar examples of how GIS can store and display a number of large datasets for the entire country quickly and easily. Without the help of GIS, you would have had to search manually through records on your computer on telephone staff at the Census office to get information about your area of interest.
With GIS, data for any area can be accessed quickly and easily according to a location. We can now store and show maps and aerial photographs covering the whole of a country. For example, Multimap through which you can know exactly where every town and village in the UK was, you would be unable to provide the level of information that Multimap is able to do in just a few seconds. Essentially, you are able to customise your data to suit your needs.
GIS software has a large variety of tools of varying levels of complexity. Shown below are some core standard functions common to GIS software packages.
Query: Ask questions of feature attributes like: where is _? What’s the nearest_? What intersects with _?
Mapping and cartography: Visualize features and edit symbology and colours to create an output map with title, scale bar, north arrow etc.
Select: Classify features and their attributes that meet some criteria.
Distance: Estimate the distance between features.
Buffers: Rings drawn around features at a particular distance from the features.
Overlay: The display of diverse layers of information at one location.
Clip: Makes an input layer to the size and extent of a selected layer.
Merge: Merges multiple layers into a single layer.
Raster analysis: A complete separate suite of tools for raster analysis which includes classifying cells, deriving aspect and slope, mosaicing and calculating new cell values among many others.
3D: Data can be analyzed with ‘height’ in 3-dimensions for powerful visualization
Who uses GIS and Why?
GIS has evolved into a technology that is used by a huge number of industries and agencies to help plan, design, engineer, build and maintain information infrastructures that effects our everyday lives.
Use of GIS in different industry
Forestry: Inventory and management of resources
Police: Crime mapping to target resources
Epidemiology: To link clusters of disease to sources
Transport: Monitoring routes
Utilities: Managing pipe networks
Oil: Monitoring ships and managing pipelines
Central and local government: Evidence for funding and policy (eg.) deprivation
Health: Planning services and health impact assessments
Environment agencies: Identifying areas of risk from e.g. flood
Emergency departments e.g. ambulance: Planning quickest routes
Retail: Store location
Marketing: Locating target customers
Military: Troop movement
Mobile phone companies: Locating masts
Land ReGIStry: Recording and managing land and property
Estate agents: Locating properties that match certain criteria
Insurance: Identifying risk e.g. properties at risk of flooding
Agriculture: Analyzing crop yields