Looking for other types of maps from USGS?
The U.S. Geological Survey (USGS) is the largest mapping agency in the United States and has published topographic maps of the nation since 1884. Their topographic map series, which shows physical landforms and features, can be useful for a wide range of research topics. Since they have been printed with uniform scales and symbols for over a century they are an excellent source for visualizing change over time.
This guide is meant to assist in finding and using topographic maps from the USGS.
Scale - The relationship of a size or distance on a map with the same size or distance on earth. Since there are 63,360 inches in one mile, one inch on a map with the scale of 1:63,360 would be one mile on earth. The scale can be represented as a fraction (e.g. 1/63,360), verbally (e.g. 1 inch = one mile), or with a scale bar. Smaller-scale maps generally show more area and less detail than larger-scale maps.
Contour Line - A line representing a continuum of points at the same elevation on a topographic map. Contour intervals are the level of elevation change between successive contour lines, and are measured in feet or meters on most maps. Areas on maps where contour lines appear close together have steeper slopes compared to contour lines with more distance between them, provided that they have the same contour interval.
Topography - Surface shapes and features represented on a map. Topography can be shown with contour lines which indicate elevation changes.
Projection - The correspondance between points on a sphere (the earth) and the points on a plane (a map). No projection transforms a sphere onto a flat surface without distortion. Projections can be used to preserve at least one of five metric features of a map: distance, area, direction, shape, and scale, but never all at once. Map makers choose a particular projection to display information based on their intended purpose of their map.
Coordinate - The position of a point with reference to an x- and y-axis. The latitude and longitude coordinate system provides an often used x-axis (prime meridian) and y-axis (equator) for determining the position of a point on the surface of the earth.
Legend - A menu for describing maps symbols.