Topographic maps are two-dimensional representations of the physical and cultural characteristics of the earth's surface. Their main purpose is to show elevation of the terrain by differentiating the physical features of the landscape (mountains, valleys, plains, shorelines, etc.). This differentiation is achieved by the use of contour lines, or lines of equal elevation, the spacing of which indicates the slope of the land - the closer the contours, the steeper the slope. These maps also show other land features such as waterways (streams, rivers, ponds) and vegetated areas, as well as various cultural features (towns and cities, road and railways, power lines, political boundaries, etc.).
Topographic maps are used for both professional applications (e.g., urban planning, road construction, geologic/environmental studies) and for recreational purposes (e.g., hunting, fishing, camping, and biking). Topo maps are produced in several sizes and scales to fit the user's needs.
The Maryland Geological Survey (MGS) sells or distributes three types of topographic maps: county topographic maps, which are prepared by MGS; 7.5-minute (or 7.5' ) quadrangle topographic maps, which are prepared by the U.S. Geological Survey (USGS); and a Maryland-Delaware topographic map, also prepared by the USGS. [Note: "minute" is a unit of angular measure, in this case units for latitude and longitude. In angular measures, the following relationships apply: 1 degree (or 1°) equals 60 minutes (60' ), and 1 minute (1' ) equals 60 seconds (60").
- County Topo Maps
- Scale - 1:62,500 or 1/62,500 (1 unit on the map = 62,500 units on the
- or 1 inch on the map equals approximately 1 mile on the ground.
Each map encompasses one full county; there are 23 counties in Maryland.
County topo maps may be pieced together to create regional maps by cutting along county and state boundary lines.
County topo maps may be purchased over-the-counter or by mail.
- Scale - 1:62,500 or 1/62,500 (1 unit on the map = 62,500 units on the ground)
- USGS 7.5-minute Quadrangle
- Scale - 1:24,000 or 1/24,000 (1 unit on the map = 24,000 units on the
- or 1 inch on the map equals 2,000 feet on the ground.
The average quad in Maryland covers an area of approximately 6.7 x 8.6 miles (roughly 58 square miles), or 7’30” (7 minutes, 30 seconds = 1/8 degree) of latitude by 7’30” of longitude; a 7.5-minute quad covers a much smaller area than any of Maryland's county topo maps. Complete coverage of Maryland requires all or part of 256 7.5-minute quads.
Quad maps are sold over-the-counter or by mail
- Scale - 1:24,000 or 1/24,000 (1 unit on the map = 24,000 units on the ground)
- USGS Topographic Map of Maryland
- Scale - 1:500,000 or 1/500,000 (1 unit on the map = 500,000 units on
- or 1 inch on the map approximately equals 8 miles on the ground
This map may be purchased over-the-counter or by mail.
- Scale - 1:500,000 or 1/500,000 (1 unit on the map = 500,000 units on the ground)
The scale of a 7.5-minute quad map is larger than the scale of a county topo map, which is in turn larger that the scale of the State map. (1/24,000 > 1/62,500 > 1:500,000) The larger the scale, the more detail can be shown. However, to keep the map at a convenient size, the larger the scale, the less geographic area can be depicted.
Pre-payment is required for all MGS publication orders. State sales tax does not apply, but postage charges do. A mailing tube for rolled maps is an additional $2.00. Please refer to the current List of Publications for details. Most orders are shipped the day of receipt, usually via UPS. Please provide street address and telephone number in the event of an order problem (no P.O. Box). Quad maps may be purchased through the USGS in Denver, Colorado, or through private distributors. See attached list.
For more information regarding topographic maps or geologic topics, visit the on-line List of Publications or contact the Maryland Geological Survey, 2300 St. Paul Street, Baltimore, Maryland 21218-5210; phone (410) 554-5505.
Compiled by the Maryland Geological
Survey, 2300 St. Paul Street, Baltimore, MD 21218
This electronic version of "Fact Sheet No.4 " was prepared by R.D. Conkwright, Division of Coastal and Estuarine Geology, Maryland Geological Survey. Please send comments on this page to Dale Shelton (firstname.lastname@example.org)