What is a GIS?

August 20, 2011 § Leave a comment

A GIS, (geographical or geospatial information system), is a:

  1. Geo-database – a spatially referenced database.
  2. Set of Maps and views – that can be queried, modified, and show features in relation to the Earth’s surface. Geo-Visualization.
  3. Model for Geo-processing – deriving new geographic datasets from existing ones.

A GIS is ‘a system to collect, store, manipulate, analyse and present spatially referenced data’. (Collection is usually done via a 3rd party, whereas analyzing and displaying are the most common uses of GIS. Manipulation is not commonly done.)

GIS is an integrating technology, it’s development has relied on many different disciplines in the social sciences, natural sciences and engineering.

Themes (layers) are a powerful idea of GIS’. These themes can be combined differently to serve different goals. They leverages the dynamic nature of GIS’, in comparison to static paper maps which are reliant on symbols.

There are two types of GIS data; raster and vector.

  1. Raster Data is where GIS’ originated from. It is based off a continuous field of data in absolute space. This model is cell-based. (The scale of the cells depends on purpose).
  2. Vector data is object orientated and comes from databases, originating in CAD/CAM. Entities can have non-spatial attributes. This model is based off relative, topological,  space. It is represented as points, lines and regions.

(These days, the traditionally significant split between vector and raster layers have been significantly reduced. However, to be combined, themes must ensure they consist of a projection.)

GIS can investigate various questions, namely questions about:

  • Location
  • Condition
  • Trend
  • Routing – (like Trend, Utilizing Cost Path Analysis here is quite common).
  • Pattern – (distribution of artifacts)
  • Modelling – (the ‘holy grail’ of GIS, usually fails, but heavily invested in, it allows for the basic prediction of the location of archaeological sites)

These questions have helped (in Archaeology) with:

  • Cultural Heritage Management
  • Excavation Recording
  • Landscape Archaeology
  • Spatial Simulation Modelling
  • 3D Stratigraphic Modelling
(See journal references for more extensive examples).
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References

  • Wilson, A., (Lecture Material) “ARCA2606 Week 04 Digital Data and GIS”, Created and Modified 19/08/2011.
  • Foote, K. E., Lynch, M., “Geographic Information Systems as an Integrating Technology: Context, Concepts, and Definitions”, <http://www.colorado.edu/geography/gcraft/notes/intro/intro.html>, last revised 2009.1.11, accessed 20/8/2011.
  • Johnson, I., Wilson, A., (2003), “Making the Most of Maps: Field Survey on the Island of Kythera”, Journal of GIS in Archaeology, Volume I—April 2003
  • Bevan, A., Conolly, J., (2003), “GIS, Archaeological Survey, and Landscape Archaeology on the Island of Kythera, Greece”, Journal of Field Archaeology, Vol. 29, No. 1/2 (Spring, 2002 – Summer, 2004), pp. 123-138
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Class Activity

As an example of different GIS Data and their capabilities, 4 maps were generated for different purposes (titled).

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