READING AND USING MAPS
What is the difference between a physical and a political map?
A physical map shows natural features of the land such as mountains, rivers, lakes, streams, and deserts. A political map shows human-made features and boundaries such as cities, highways, and countries. The maps we use in atlases and see on the walls of classrooms are typically a combination of the two.
What is a topographic map?
A topographic map shows human and physical features of the Earth and can be distinguished from other maps by its great detail and by its contour lines indicating elevation. Topographic maps are excellent sources of detailed information about a very small area of the Earth. The United States Geological Survey (USGS) produces a set of topographic maps for the United States that are at a scale of 1:24,000 (one inch equaling 2,000 feet [or 1 centimeter equaling about 240 kilometers]). You can purchase these maps online, at sporting goods stores, or through the USGS itself.
Why are road maps so difficult to fold?
The problem lies with the multitude of folds required to return the map to its original, folded shape. The easiest way to fold a road map is to study the creases and to fold the map in the order that the creases will allow. But once you've made a mistake, the folds have lost their tell-tale instructions. To fold a road map, begin by folding it accordion style, making sure that the "front" and "back" of the folded design appear on top. Then, once the entire map is folded accordion style, fold the remaining slim, long, folded paper into three sections. And, voil`, your road map is folded!
Why is color important on a relief map?
A relief map portrays various elevations in different colors. But, a common color scheme found on relief maps causes a problem. On these maps, mountains are displayed as red or brown while lowlands are shown in shades of green. This is confusing because the green areas on the map are often misconstrued as fertile land while brown areas are mistaken for deserts. For example, an area such as California's Death Valley, which is shown in green on relief maps because it lies below sea level, seems fertile, when actually it is an inhospitable desert.
What does the scale of a map tell me?
A scale indicates the level of detail and defines the distances between objects on a map. On a map, scales can be written as a fraction, a verbal description, or as a bar scale.
A fraction, or ratio, using the example of 1/100,000 or 1:100,000, indicates that one unit of any form of measurement on the map is equivalent to 100,000 units of the same measurement in the area being represented. For instance, if you use inches as the unit of measurement, then one inch on the map would equal 100,000 inches in the area represented by the map.
A verbal description describes the relationship as if it were a verbal instruction, such as "one inch equals one mile." This allows the versatility of having different units of measurement.
A bar scale uses a graphic to show the relationship between distance on the map to distance in the area represented. The bar scale is the only type of scale that allows a reduction or enlargement of the map without distorting the scale. This is because when you increase the size of the map, the bar scale is increased proportionally. For a fraction or verbal scale, the proportion (1:1,000) is only true for the map at that size. For example, when enlarging a map, the map might become twice as large but the numbers in a ratio do not change, as they would need to in order to stay accurate.
How can I determine the distance between two places by using a scale?
By using a ruler, compare the distance between two points on a map with the information on the scale to calculate the actual distances between the two points. For example, if you measure the distance between two towns as being five inches and the ratio says 1:100,000, then the actual distance between the towns is 500,000 inches (7.9 miles [12.7 kilometers]).