Essentials of Geography

Tools of the Geographer

Maps

A map is the fundamental tool of the geographer. With a map, one can illustrate the spatial distribution (i.e., geographic pattern) of almost any kind of phenomena. Maps provide a wealth of information. The information collected to create a map is called spatial data. Any object or characteristic that has a location can be considered spatial data. The data collected for a map can be qualitative (buildings, rivers, roads) or quantitative (elevation, air temperature, population density). There are many different kinds of maps that serve quite different purposes.

Map projections

A map projection is a method of portraying the two-dimensional curved surface of the Earth on a flat planar surface. Projections are created to preserve one or several measurements of the following qualities:

• Area
• Shape
• Direction
• Bearing
• Distance
• Scale

Each projection handles the conversion of these metric properties from the curved surface of a globe to the flat surface of map differently.

The purpose of the map is of primary importance in choosing a projection to illustrate spatial patterns of Earth phenomena. For instance, the Mercator projection was long used for navigation or maps of equatorial regions. The cylindrical Mercator projection mathematically projects the globe onto a cylinder tangent to the Equator. Large areas become distorted which increases toward away fromthe Equator. Distances are true only along the Equator, special scales are provided for other latitudes for measurement.

Figure EG.9 Cylindrical Mercator projection
(Courtesy USGS - Source)

The Robinson projection uses tabular coordinates rather than mathematical formulas to make earth features look the "right" size and shape. A better balance of size and shape result is a more accurate picture of high-latitude lands like Russia, Soviet and Canada. Greenland is truer to size but compressed.

EG.10 Robinson projection
(Courtesy USGS - Source)

For more on projections see: Map Projections from the United States Geological Survey.

Types of Maps

Reference Maps: Topographic

Reference or navigational maps are created to help you navigate over the earth surface. These kinds of maps show you where particular places are located and can be used to navigate you way to them. A street map or the common highway road map falls into this category. Physical geographers use topographic maps to show the locations of landscape features on the earth.

Figure EG.11 Sample Topographic map
Source: USGS Monarch Lake

Topographic maps illustrate the horizontal and vertical positions (relief) of land surface features. Topographic maps use contour lines to show elevation (height above sea level). Contour lines connect points of equal elevation above a specified reference, usually as sea level. The heavy brown contour lines with the elevation printed on them are called index contours. Intermediate contours are the lighter brown lines between index contours. Sometimes dashed lines called supplemental contours are used in areas of very low relief. Benchmarks are locations where the elevation has been surveyed. Benchmarks are denoted on a map with the letters "BM", "X" or a triangle with the elevation printed beside.

Not only are natural features like mountains, valleys, streams and glaciers portrayed, but cultural features as well, e.g., houses, schools, streets, urbanized area. Take a look at the topographic symbol sheets provided by the United States Geological Survey to get an idea of the information provided on them.

Figure  EG.12 Shaded Relief Map
Source: USGS "Working with Maps"

Colors and shading can also be used to illustrate relief. Shaded relief maps are great at giving us the over all shape of the surface, but can’t help us much in determining the elevation of a particular place. The National Geographic Society is noted for its excellent map products (and magazine too). Satellite maps are particularly useful to illustrate relief  .

Thematic Maps

Thematic maps are used to communicate geographic concepts like the distribution of densities, spatial relationships, magnitudes, movements etc. World climate or soils maps are notable examples of thematic maps. Figure EG.13 is a map that shows population density of Canada as colored polygons and the distribution of major earthquakes felt throughout the country. Graduated circles indicate the area over which the earthquakes were felt. This map was created using a geographic information system which has the capability of overlying different kinds of spatial data to show the relationships between them.

Figure EG. 13 Major earthquakes felt in Canada. Source: NAISMap WWW-GIS