Section 1.3:
The Geographer's Toolbox:
Location, Maps, Remote Sensing, and GIS

Geographers use many different tools to represent the world in a convenient form for examination and analysis. Different kinds of images and data are needed to study vegetation change in Brazil or mining activity in Mongolia; population density in Tokyo or language regions in India; religions practiced in Southwest Asia or rainfall distribution in southwestern Australia. Knowing how to display and interpret information in map form is part of a geographer’s skill set. In addition to traditional maps, today’s modern satellite and communications systems provide an array of tools not imagined 50 years ago.

Latitude and Longitude

To navigate their way through daily tasks, people generally use a mental map of relative locations to locate specific places in terms of their relationship to other landscape features. The shopping mall is near the highway, for example, or the college campus is near the river. In contrast, map makers use absolute location, often called a mathematical location, which draws on a universally accepted coordinate system that gives every place on Earth a specific numerical address based on latitude and longitude. The absolute location for the Geography Department at the University of Oregon, for example, has the mathematical address of 44 degrees, 02 minutes, and 42.95 seconds north and 123 degrees, 04 minutes, and 41.29 seconds west. This is written 44° 02′ 42.95″ N and 123° 04′ 41.29″ W.

Lines of latitude, often called parallels, run east–west around the globe and are used to locate places north and south of the equator (0 degrees latitude). In contrast, lines of longitude (or meridians), run from the North Pole (90 degrees north latitude) to the South Pole (90 degrees south latitude). Longitude values locate places east or west of the prime meridian, located at 0 degrees longitude at the Royal Naval Observatory in Greenwich, England (just east of London) (Figure 1.16). The equator divides the globe into northern and southern hemispheres, whereas the prime meridian divides the world into eastern and western hemispheres; these latter two hemispheres meet at 180 degrees longitude in the western Pacific Ocean. The International Date Line, where each new solar day begins, lies along much of 180 degrees longitude, deviating where necessary to ensure that small Pacific island nations remain on the same calendar day.

Each degree of latitude measures 60 nautical miles or 69 land miles (111 km) and is made up of 60 minutes, each of which is 1 nautical mile (1.15 land miles). Each minute has 60 seconds of distance, each approximately 100 feet (30.5 meters).

From the equator, parallels of latitude are used to mathematically define the tropics: The Tropic of Cancer at 23.5 degrees north and the Tropic of Capricorn at 23.5 degrees south. These latitude lines denote where the Sun is directly overhead at noon on the solar solstices in June and December. The Arctic and Antarctic circles, at 66.5 degrees north and south latitude respectively, mathematically define the polar regions.

Global Positioning Systems (GPS) 

Historically, precise measurements of latitude and longitude were determined by a complicated method of celestial navigation, based on one’s location relative to the Sun, Moon, planets, and stars. Today absolute location on Earth (or in airplanes above Earth’s surface) is determined through satellite-based global positioning systems (GPS). These systems use time signals sent from your location to a satellite and back to your GPS receiver (which can be a smartphone) to calculate precise coordinates of latitude and longitude. GPS was first used by the U.S. military in the 1960s and then made available to the public in the later decades of the 20th century. Today GPS guides airplanes across the skies, ships across oceans, private autos on the roads, and hikers through wilderness areas. In the future, such systems will guide driverless cars. While most smartphones use locational systems based on triangulation from cell-phone towers, some smartphones are capable of true satellite-based GPS accurate to 3 feet (or 1 meter).

Map Projections

Because the world is a sphere, mapping the globe on a flat piece of paper creates inherent distortions in the latitudinal, or north–south, depiction of Earth’s land and water areas. Cartographers (those who make maps) have tried to limit these distortions by using various map projections, defined as the different ways to project a spherical image onto a flat surface. Historically, the Mercator projection was the projection of choice for maps used for oceanic exploration. However, a glance at the inflated Greenlandic and Russian landmasses shows its weakness in accurately depicting high-latitude areas (Figure 1.17). Over time, cartographers have created literally hundreds of different map projections in their attempts to find the best ways to map the world while limiting distortions.

For the last several decades, cartographers have generally used the Robinson projection for maps and atlases. In fact, several professional cartographic societies tried unsuccessfully in 1989 to ban the Mercator projection for world maps because of its spatial distortions. Like many other professional publications, maps in this book utilize the Robinson projection.

Map Scale

All maps must reduce the area being mapped to a smaller piece of paper. This reduction involves the use of map scale, or the mathematical ratio between the map and the surface area being mapped. Many maps note their scale as a ratio or fraction between a unit on the map and the same unit in the area being mapped, such as 1:63,360 or 1/63,360. This means that 1 inch on the map represents 63,360 inches on the land surface; thus, the scale is 1 inch equals 1 mile. Although 1:63,360 is a convenient mapping scale to understand, the amount of surface area that can be mapped and fitted on a letter-sized sheet of paper is limited to about 20 square miles. At this scale, mapping 100 square miles would produce a bulky map 8 feet square. Therefore, the ratio must be changed to a larger number, such as 1:316,800. This means that 1 inch on the map now represents 5 miles (8 km) of distance on land.

Based on the representative fraction, the ratio between the map and the area being mapped, maps are categorized as having either large or small scales (Figure 1.18). It may be easy to remember that large-scale maps make landscape features like rivers, roads, and cities larger, but because the features are larger, the maps must cover smaller areas. Conversely, small-scale maps cover larger areas, but must then make landscape features smaller.

Map scale is probably the easiest to interpret when it is a graphic or linear scale, which visually depicts distance units such as feet, meters, miles, or kilometers on a horizontal bar. Most of the maps in this book are small-scale maps of large areas; thus, the graphic scale is in miles and kilometers.

Map Patterns and Map Legends

Maps depict everything from the most basic representation of topographic and landscape features to complicated patterns of population, migration, economic conditions, and more. A map can be a simple reference map showing the location of certain features, or a thematic map displaying data such as religious affiliations or popular tourist attractions in a city. Most of the maps in this text are thematic maps illustrating complicated spatial phenomena. Every map has a legend that provides information on the categories used in the map, their values (when relevant), and other symbols that may need explanation.

One type of thematic map used often in this book is the choropleth map in which color shades represent different data values, with darker shades generally showing larger average values. Per capita income and population density are often represented by these maps, with data divided into categories and then mapped by spatial units such as countries, provinces, counties, or neighborhoods. The category breaks and spatial units selected can have a dramatic impact on the patterns shown in a choropleth map (Figure 1.19).

Aerial Photos and Remote Sensing

Although maps are a primary tool of geography, much can be learned about Earth’s surface by deciphering patterns on aerial photographs taken from airplanes, balloons, or satellites. Originally available only in black and white, today these images are digital and can exploit visible light (like a photograph) or other light wavelengths such as infrared that are not visible to the human eye.

Even more information about Earth comes from electromagnetic images taken from aircraft or satellites, termed remote sensing (Figure 1.20). Unlike aerial photography, remote sensing gathers electromagnetic data that must be processed and interpreted by computer software to produce images of Earth’s surface. This technology has many applications, including monitoring the loss of rainforests, tracking the biological health of crops and woodlands, and even measuring the growth of cities. Remote sensing is also central to national defense, such as monitoring the movements of troops or the building of missile sites in hostile countries.

The Landsat satellite program launched by the United States in 1972 is a good example of both the technology and the uses of remote sensing. These satellites collect data simultaneously in four broad bands of electromagnetic energy, from visible through near-infrared wavelengths, that is reflected or emitted from Earth. Once these data are processed by computers, they display a range of images, as illustrated in Figure 1.20. The resolution on Earth’s surface ranges from areas 260 feet (80 meters) square down to 98 feet (30 meters) square.

Commercial satellite companies such as DigitalGlobe now provide high-resolution satellite imagery down to 1.5 feet (or 0.5 meters) square. This means that a car, small structure, or group of people would be easily seen, but an individual person would not. Of course, cloud cover often compromises the continuous coverage of many parts of the world.

Geographic Information Systems (GIS)

Vast amounts of computerized data from sources such as maps, aerial photos, remote sensing, and census data are brought together in geographic information systems (GIS). The resulting spatial databases are used to analyze a wide range of issues. Conceptually, GIS can be considered a computer system for producing a series of overlay maps showing spatial patterns and relationships (Figure 1.21). A GIS map, for example, might combine a conventional map with data on toxic waste sites, local geology, groundwater flow, and surface hydrology to determine the source of pollutants appearing in household water systems.

Although GIS dates back to the 1960s, it is only in the last several decades—with the advent of desktop computer systems and remote sensing data—that GIS has become absolutely central to geographic problem solving. It plays a central role in city planning, environmental science, public health, and real-estate development, to name a few of the many activities using these systems. GIS and other spatial tools and techniques are also critical in uncovering the patterns that allow geographers to address the themes discussed in the rest of this chapter and in the rest of the book.

Physical Geography and Environmental Issues: The Changing Global Environment

Chapter 2 provides background on world physical and environmental geography, outlining the global environmental elements fundamental to human settlement—landforms, climate, vegetation, hydrology, and energy. In the regional chapters, the physical geography sections explain the environmental issues relevant to each world region, covering such topics as climate change, sea-level rise, acid rain, energy and resource issues, deforestation, and wildlife conservation. Each regional chapter addresses specific environmental problems, but also discusses policies and plans to resolve those issues (see Working Toward Sustainability: Meeting the Needs of Future Generations).