Task All human activities require knowledge about the Earth. Geographic representation is concerned with the Earth's surface or near surface. In order to build a representation of it, it is necessary to make choices about what to represent, at what level of detail, and over what time period, etc. Read this section from Longley et al. (2001) paying particular attention to the discussion about discrete objects and fields.

As well as our initial cognition of the world we should also consider the ways in which our understanding is represented through the maps we produce. Foote & Crum (1995) remind us of the value of a 'good' map.

Representing Geography
[ pdf ]
Source: Longley P A, Goodchild MF, Maguire DJ and Rhind DW, 2001. Representing Geography. Geographic Information Systems and Science. John Wiley & Sons, Ltd. p. 60 - 71.
Cartographic Communication
[ URL ]
Source: Foote K and Crum S, 1995. Cartographic Communication, Geographer's Craft. <http://www.colorado.edu/geography/gcraft/notes/cartocom/cartocom_f.html> URL last validated 05-11-2007.
Task What are we doing? The world we live in is a round globe but we have spent several centuries drawing maps on flat paper. It was back in the C16th when Gerardus Mercator developed a cylindrical projection. Since then each and every time we map a sphere to a flat surface we distort the geography of the things we are trying to describe. This raises two questions - What are the problems caused by these distortions? How can we transform data between different projection and coordinate systems so that all data are spatially aligned? Your primary task is to answer these questions.

You might also like to consider two issues. Firstly, to what extent can modern applications in GI abandon the 'ancient' methods of mapping position? Over several centuries a global location referencing system developed organized around meridians of longitude and parallels of latitude. It works for mariners, cruise missiles and atlas publishers, and doesn't seem to have any serious bugs (unless you consider the fact that the earth isn't a perfect sphere as a bug). As modern GIS handle 3D coordinate geometry there is simply no need to figure the Earth mapped to the plane paper or to any other plane. To put it simply, let us deal with data that originates in a 3D real world by recording it in a global 3D virtual environment. We can always degrade it to a 2D projection on request!

So far you have focused on the representation of physical space. Can you identify examples when an alternative (non-geodetic) representation of space is perfectly adequate e.g. topology?

From Map Projections to Virtual Geography
[ URL ]
Use this applet to experiment with different map projections. It is suggested that you first experiment by entering the easting and northing (longitude, latitude) coordinates of where you live and observe the effect of changing the projection.

Source: Bottomley H, 2002. Java world map projections. <http://www.btinternet.com/%7Ese16/js/mapproj.htm> URL last accessed 05-11-2007.

The Shape of the Earth
[ URL ]
A well-written introduction to geodesy - the study of the Earth's shape. With an emphasis on cartography it is not surprising that the graphics are of a good quality.

Source: Furuti C, 1997. The shape of the Earth, in Cartographical Map Projections. <http://www.progonos.com/furuti/MapProj/Normal/TOC/cartTOC.html> URL last validated 05-11-2007.

Map Projection Overview
[ URL ]
A traditional tutorial on map projections with additional material on datums and coordinate systems.

Source: Dana P, 1999. Map projection overview, in The Geographer's Craft. <http://www.colorado.edu/geography/gcraft/notes/mapproj/mapproj_f.html> URL last validated 05-11-2007.

Task
Supplement
Once you understand the importance of map projections and coordinate systems then you should explore how they are handled in a GIS application. Your task is to find out how ESRI ArcGIS does it. You should listen to the free seminar on geographic and projected coordinate systems and then examine the effects of using different spheroids in ArcGIS in the first module of the Virtual Campus course.
Working with Map Projections and Coordinate Systems in ArcGIS
[ URL ]
Source: ESRI (unknown). Working with Map Projections and Coordinate Systems in ArcGIS. ESRI Training Seminar. <http://training.esri.com/acb2000/showdetl.cfm?DID=6&Product_ID=826> URL last accessed 05-11-2007.
Sizing Up the Earth
[ URL ]
Source: ESRI (unknown). Sizing up the Earth, Module 1 in Understanding Map Projections and Coordinate Systems. ESRI Virtual Campus course. <http://training.esri.com/acb2000/showdetl.cfm?DID=6&Product_ID=697> URL last accessed 05-11-2007.
Task
Reexamine your geographical diary. How did you choose which events and objects to record? At which scale(s) did you conceptualise them? If you were to maintain a spatial blog how would you represent them? Your task is to formalise the ideas contained in your diary by selecting and applying scale, projection and coordinate systems.
Plazes
[ URL ]
Source: Plazes.com <http://plazes.com/tools/widget> URL last accessed 05-11-2007.
Where's Ed?
[ URL ]
Source: Parsons E, (unknown). Where's Ed? www.edparsons.com <http://www.edparsons.com> URL last accessed 05-11-2007.
Task
Read Couclelis (1999) and consider how you could represent time. How surprised would you be if I told you that very few implementations of GIS formally recognise a temporal dimension in their design?
Space, Time, Geography Source: Couclelis H, 1999. Space, time, geography, Ch 2 In Longley PA et al. (eds.), Geographical Information Systems: principles, techniques, management & applications. New York: Wiley. p. 29-38.