Using an atlas

Introduction

An atlas is essentially a large collection of maps. A map is a diagrammatic representation of the Earth's surface, when looking straight down on it. An atlas features many different types of maps, which display information using a variety of techniques. Atlases also include additional information in the form of illustrations, tables, diagrams and graphs. An atlas is not only useful when trying to find places, but also when obtaining and comparing information on different areas around the world.

Types of maps in atlases

Maps provide the majority of information in an atlas. Some maps in an atlas feature all of the Earth's surface. Other maps are of continents, countries, or smaller and more specific regions. Maps are a popular way of displaying information, because the data from one location can be easily and effectively compared and contrasted with other regions.

The two most common types of maps found in atlases are political maps and physical maps. Political maps are representations of a country's territory, borders and capital city. Physical maps show the size, shape and slope of landforms on the Earth's surface. This includes physical features such as mountain ranges, deserts, lakes and rivers. The information provided by political maps and physical maps is sometimes combined to form reference maps. These three types of maps show information classified as quantitative data. Quantitative data can be measured, counted and compared.

See Image 1

There are also maps featured in atlases which represent information classified as comparative data. This data is a scientific comparison between different facts. Comparative data includes environmental elements, such as the information found in rainfall maps, as well as population distribution and density, which can be seen in population maps. Comparative data can also be found in such maps as landuse maps and vegetation maps.

Mapping techniques

Depending on what is being represented, it is not always effective or even possible to organise and display different types of information in the same way. To overcome this problem, a number of mapping techniques have been developed. Many of these techniques are featured in an atlas.

Colour and variation

Political maps use different colours to distinguish between the territories of different countries (or states). Physical maps feature shading and variations in colour, achieving a light and shadow effect which clearly depicts the varying elevation of surface features. The use of variations in colour is also evident in choropleth mapping. Choropleth maps show density and concentration patterns by using dark shades (to represent 'more' of something) and light shades (to represent 'less') of the same colour. This technique is used to represent anything from voting patterns to water usage.

Lines and dots

Isolines connect points which are of the same value or quantity. They include contour lines, which are used on topographic maps (show height, shape and slope of surface features), to show points which are of the same height above sea level. Isolines also include isobars, which connect points of equal air pressure on synoptic charts.

While contour maps use lines to show distribution, flow maps use lines to show movement patterns. The volume and destination can be represented in flow maps, to show such things as migration and trade.

Some maps use dots to represent the occurrence of a feature. These dots are a useful way of showing location, distribution and density. Dot maps are an effective way of showing population statistics. See Image 2

Other methods used to show information in an atlas

Despite there being a number of methods used to display information on a map, maps are not always the best way to convey information. In some cases, it is more interesting and less complicated for information to be expressed as an illustration, table, diagram or graph. It is the responsibility of the cartographer (person who creates maps) to determine which type of graph or diagram is best suited to show particular information.

An atlas features a wide variety of graphs and diagrams. The most common are line graphs, bar or column graphs and pie charts. Line graphs are particularly useful when showing the relationship or change of something over time. The simple format of bar and column graphs makes them ideal for comparing different statistics. Since pie charts are divided into proportions of a whole, they are often used to show composition. See Image 3

Using an atlas

An (hardcopy) atlas is generally structured like most other reference books. At the front of the atlas there is usually a contents page(s), which lists all of the maps that are featured in the book and what pages they can be found at. The main content of the atlas is essentially many different types of maps that feature anything from entire continents to small towns and cities. At the back of the atlas there is usually an index page(s). The index page lists all of the countries, cities and towns which can be found in the atlas. Beside the listings, there is usually a page reference, a grid reference (comprising a letter and a number) and a latitudinal and longitudinal reference. Latitude is a measurement of how far north or south of the equator something is located. Longitude is a measurement of how far east or west of the Greenwich Meridian (also known as the Prime Meridian) it is. (Refer Topic 2, Chapter 1: Locating features on a map- latitude and longitude).