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Topographic maps terms
Terms in this set (40)
A point of known elevation above or below a datum plane, usually sea level, given to the nearest foot and indicated on a map as "BM"
The vertical distance between two adjacent contour lines.
A line drawn on a topographic map connecting two points of equal elevation above sea level.
The zero plane or base reference level from which all elevations on a map are measured, usually sea level.
The highest land area separating two adjacent river drainage systems, steams or valleys.
The distance an object or feature is above the datum plane. Elevations on U.S.G.S. topographic maps are above or below sea level.
A slope, particularly a stream or land surface. Measurements are expressed in percent, feet per mile (m/Km), or degrees.
referred to as TRUE NORTH and indicated in the declination symbol on the map as a lone pointing to a "star"
Shown in the declination symbol with a line point to a GN.
The measure of angular distance north and south from the equator. On topographic maps, this is indicated at the corners of the northern and southern borders of the map.
The measure of angular distance east and west from the zero degree longitude(Prime Meridian). On topographic maps, this is indicated at the corners of the eastern and western borders of the map.
Magnetic North 1
The amount, in degrees and directions, the needle of a magnetic compass deviates from true north. The magnetic north pole is at a different position on the globe than the geographic north pole resulting in this deviation.
The one line that has no deviation.
a line joining points of equal deviation
Magnetic North 2
The declination symbol on the topographic has a line point to MN. Since the magnetic pole wanders over time it is necessary to know the current declination of the area covered by the map to be able to orient the map, and have the most recent publication of the map.
A map area within designated boundary of meridians and parallels.
The difference in elevation between the high point and low point for a specific region of the Earth surface. EX: North American, Arizona, a U.S.G.S. Topographic maps, etc.
The ratio of linear measurement on a map to what the distance actually measures on the Earth surface. On a map with a ratio scale of one inch to one mile scale would be represented as 1: 63,360. Ex: one inch on the map represents 63,360= one mile on the earth. Remember, in ratios, whatever unit of measurement is on the left of the ratio sign the same units mus be used on the right side.
A graphic representation of position, scale, shape, relief, and distribuation of selected natural and cultural features of an area of the Earth's surface.
The surface configuration of the earth. Ex: Mountians, hills, plateaus, plains, valleys, and may also include changes made by humans such as canals, landfills, levees. etc.
United States Coast and Geodetic Survey, a federal bureau of the department of commerce responsible for maintaining surveys of the coastal and interior waterways of the United States and its possessions.
United States Geologic survey, a federal bureau of the department of Interior, reponsible for land surveying and mapping the land area of the United States and its possessions
On the United States Geological Survey maps (U.S.G.S. quadrangles) longitude lines extend north-south and latitude east-west. North is at the top of the map, east to the right, west left and south at the bottom of the page.
Name of the map
The name given to each map is in the margin of the upper and lower right corners, along with, the state or states in which the area is located. The name given to the quadrangle is taken from a city, town, or prominant physical feature within the limits of the area mapped.
Location of the map
The location of the quadrangle is given by state and the longitude and latitude at each corner of the map. On some quadrangles there is an outline of the state and a small black rectangle pinpoints the map's location.
As an aid obtaining topographic maps, the U.S.G.S. furnished an index max of each state, which incidicates each published quadrangle for the state with its name and map scale.
Survey and Publication Data
The upper margin provides information on what agency did the mapping. The lower margin gives the dates of the survey, revisions and reprintings. The dates mat be important since many of the other maps are not as accurate or reliable.
On most maps( not all) information on the magnetic declination is provided. This is especially if the mapping was done from a magnetic compass. Since the magnetic declination changes from year to year it is necessary, fro proper orientation, to ascertian the amount and direction of change since the date the map produced. The magnetic declination is expressed in degrees east or west of true north.
Size of the map
The size of a topographic map is expressed in degrees of longitude and latitude, EX. the standard maps cover 15 minutes of arc of the globe, or 1/4 of a degree and are referred to as the 15 minute series (1:62,500) Each map covers 15 minutes of arc north-south and east-west. Series (1:24,000) available. This is a larger scale map and only covers about 25% of the area of a 15 Minute Series quadrangle. however, it is a map with a great deal more detail.
Used for showing topography, the relief and configuration of the surface of the land area. All contour lines are brown as well as sand areas, gravel beaches and tailing ponds.etc.
All water features including oceans, lakes, glaciers, rivers, and streams, ponds, springs, marshes, wells, and canels.
Cultural or man-made features such as houses and other buildings, certian roadways, trails, railroads, power lines, national, sate, and county lines, survey points and bench marks, place names, dams, locks, docks. etc.
Additional cultural features including main highways, land survey township lines and number, and boundries of national parks.
Used for urban updates, Ex: an overprint of existing maps to show changes in urnam patterns and growth.
Small scale map
Large land area, maximum reduction, minimum detail
Large scale map
Small land area, minimum reduction, maximum detail
This scale consists of a line subdivided into one inch (one centimeter) units that represent miles (kilometers) on the actual earth. The units used for the scale must be given under the scale line in miles, kilometers or possibly other types of units of linear measurement. The graphic scale is most commonly emplyed on maps designed for public school and general use because they are most easily interpreted. There is also the advantage that in case that map is enlarged or reduced by photography, the scale is proportionally changed and remains correct. On U.S.G.S. topographic maps the 0 is placed one unti from the left of the graph then the mile to the lft of the 0 is subdivided into units of 1/10 of a mile.
Ex: 1 0 1 2 3
Ratio (or fractional) Scale
A ratio scale is a fraction, expressed in the from of a retio and is the relationship between the distance on the map compared to the actual distance that represents on the earth surface. If it is expressed as a fraction it is called representative fraction or RF on the map. Since there are 63,330 inches the mile, an inch to the mile is expressed as a:
1: 24,000 = 1 inch to 2,000 feet( 7.5 quadrangle maps)
1: 62,500 = 1 inch to .986 miles (approx. 1 mile)
1: 125,000 = 1 inch to 2 miles
1: 250,000 = 1 inch to 4 miles
1: 500,000 = 1 inch to 8 miles
1 : 1,000,000 = 1 inch to 16 miles ( a "millionth" map of the world)
A verbal scale is written in sentence format, although otehr formats are used. For example, if one inch on the map represents one mile on the earth, the verbal scale is written. ONE INCH REPRESENTS ONE MILE. Another scale might be written " one inch represents 150 miles' The distance on the map is given first, and the direction to write the name of miles in words or numbers depends on the number of miles involved, usually anything over twenty miles is expressed in numerical form.
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