U.S. Geological Survey and Scales of Other Countries

The first features usually noticed on a topographic map might be the contour lines, shown in brown. Other major features such as vegetation (green), water (blue), and densely built-up areas (gray or red) are easily recognized. A grid also overlies the entire map. The grid generally represents a one-mile-square unit. This unit is an administrative land parcel system referred to as a section. Geodesic lines will also be evident, a universal land system established throughout the United States by the U.S. Geological Survey.

Both natural and man-made features are shown by lines that may be straight, curved, solid, dashed, dotted, or in any combination. The colors used generally indicate similar types of information: topographic contours (brown); lakes, streams, irrigation ditches, and other water-related features (blue); land grids and important roads (red); and other roads and trails, railroads, boundaries, and other cultural features (black). Again, refer to a map’s legend, or go to the USGS website for legend clarification.

Names of places, including cities, towns, counties, and other places or prominent landscape features, are shown in a color corresponding to the feature type. Many features and place names are identified with labels, such as Old Faithful Village, Mississippi River, Los Angeles, Substation, or Golf Course.

Most countries of the world have established a national map system similar in many ways to that of the United States. While the maps produced by various countries have much in common graphically, unique variations do exist. One should refer to the map legend to better understand the information presented. One of the distinguishing features of various countries’ map systems is whether maps use the metric system of measurement or the imperial (feet and inches) system. The United States is one of the few countries still using the imperial system.

The U.S. Geological Survey publishes maps at various scales. The scale used for most U.S. topographic mapping is 1:24,000. USGS maps at this scale cover an area measuring 7.5 minutes of latitude and 7.5 minutes of longitude, and are commonly called 7.5-minute quadrangle maps. Map coverage for most of the United States has been completed at this scale, except for Puerto Rico, which is mapped at 1:20,000 and 1:30,000, and for a few states that have been mapped at 1:25,000. Most of Alaska has been mapped at 1:63,360, with some populated areas also mapped at 1:24,000. For countries where the metric system is used, map scales follow the same proportional system, whereby 1:10,000 means one unit, (such as one centimeter) equals 10,000 units (e.g., centimeters), or one meter equals 10,000 meters. With practice and a degree of curiosity one can quickly become conversant with such maps and effective at using maps of all types for a variety of professional purposes.