The basic definition of a map
A map is a diagrammatic representation of an area of land or sea. It shows physical features such as constructed cities or roads, as well as natural landforms like mountains, rivers and cliffs. The purpose of a map is to depict spatial relationships between features. A map can vary from being a highly schematic piece of artwork right through to a meticulously detailed representation of geographic data depending on the purpose of the map.
Map types Understanding maps and their purpose
Cartography is the art of creating maps, and it has evolved over many thousands of years to be as we know it today. Now maps are no longer basic cave drawings but instead produced using computers and other technologies and distributed to the masses.
People create maps for different purposes depending on their audience and what information they need to convey.
Some different map types include:
- Physical maps: Depict information on physical features like creeks, mountains and constructed features. Symbols, colours and tinting illustrate variation.
- Climate maps: General information about climate and weather in a region (e.g. rain, snow, temperature). Colour depicts variation.
- Resource maps: Show different types of natural resources or economic activity in an area. Symbols show activities; colours show differences in land elevation.
- Road maps: Show minor and major roads and other human infrastructure e.g. buildings.
- Political maps: Show human depicted political boundaries such as private properties, land tenures and National Parks.
- Topographic maps: show the shape of the landscape using contour lines. Lines far apart indicate flat ground; lines close together indicate steep ground.
Topographic maps Understanding topographic maps and their purpose
Topographic or ‘topo’ maps are a specific type of map that shows the shape of the land. The map shows 3D landforms on a 2D surface and can be done via colour variation or contour lines that show elevation information too.
Topographic maps are handy tools for planning bushwalking trips and navigating through the bush. Maps enable bushwalkers to plan routes, communicate points of interest and tracks, and keep a track of where they are in relation to resources like water and shelter.
Bushwalkers love topographic maps because they:
- Simplify complex patterns.
- Facilitate visual connections between landforms.
- Enable communication with other walkers, rescue organisations, people at home, etc.
- Allow bushwalkers to extract useful info and plan a route to include campsites and water sources, avoid scrubby areas and select good walking ridges.
- Provide a universal tool of communication between bushwalkers to share trip routes, campsites, water sources, etc. with others.
Datum and Projection Understanding about datum and projection
All mapmakers have to overcome the fundamental mathematical problem of portraying a spherical object onto a 2D surface. Modern map-makers solve this by taking a ‘datum’, that is, a 3-D representation of the earth, and projecting it onto a 2D plane (i.e. Cartesian x-y coordinates).
This image is the typical one of the Earth centred around Europe. It is produced by converting the curved, spherical lines of longitude and latitude into a flat plane grid of perpendicular lines, but it is severely distorted at the poles.
That’s why although Greenland appears almost same size as Australia on the world map, it’s only a third of the size:
No model or projection is perfect for every part of the globe, and different countries preference some projections over others to suit their needs.
In Australia, the modern MGA reference system uses the Universal Transverse Mercator projection of the Geocentric Datum of Australia 1994 (GDA94), providing a relatively universal reference system at least for the purpose of recreational bushwalking.