Chapter 9 Vocabulary: Topographic Maps

verbal scale

"One inch represents one mile"

fractional scale

1/24,000

1m= ___cm

100 cm

1 km= ___m

1000 m

1 ft = ____ in

12 in

ratio scale

1: 24000

1 in= ___cm

2.54 cm

1 m= ___ft

3.28 ft

1 mi= ___ ft

5280 ft

ranges

6 mile wide columns running north and south parallel to principal meridians

townships

6 mile wide rows extending east-west parallel to base lines

map

A flat representation of part of Earth's surface as viewed from above and reduced in size to fit a sheet of paper/computer screen

planimetric map

A map that represents only the horizontal (2-D) positions of features (streams, landmarks, roads, political boundaries)

benchmark

A permanent reference mark (usually metal plate) placed by USGS, BLM, and other associations of government established for use by surveyors in measuring differences in elevation.

IERS

International Earth Rotation and Reference Systems Service

lidar

Light Detection and Ranging; laser to measure distances very accurately

NAD27

North American Datum of 1927

PLSS

U.S. Public Land Survey System established in 1785 when U.S. government required a way to divide public land west of the 13 original colonies into small parcels that could be transferred to ownership by private citizens

azimuth

a horizontal angle measured clockwise from north to the line you are interested in

topographic map

a map that shows the surface features (horizontal positions) of Earth like planimetric map but includes topographic contours

magnetic north pole

an area pointed to by a compass based on the Earth's magnetism; situated near geographic north pole

bearing

azimuth along a line from one point to another

relief

change in elevation; the difference (subtract) in elevation between the highest and lowest parts of an area

parallels

circles of latitude that are parallel to the equator and semicircles (meridians) of longitude that extend from pole to pole

contour lines

connect all points on a map with equal elevation. The spacing of contour lines tells you the general shape of the land surface. If the lines are closely spaced, the terrain is steep; if the lines are widely spaced, the terrain is more gentle/flat.

The colors black/red on a topographic map represent ___

cultural features

topographic profile

depicts the shape of the ground surface on a vertical plane between 2 points on the ground surface, as in side view

orthoimages

digitized aerial photographs or satellite images that have been orthorectified, corrected for distortions until they have the same geometry and uniform scale as a topographic map

compass bearing

directions towards which you are headed

point cloud

each point represents a point on Earth's surface that was hit by the lidar laser as the aircraft flew over and whose position in space was resolved during the subsequent analysis; points colored by elevation (3-D look)

base lines

east-west lines

latitude bands

east-west segments

spot elevations

elevations of specific points on topographic maps (peaks, bridges, survey, points, etc.) beside a small triangle, black dot, or x symbol

topography

features that make up the surface of the Earth and their position relative to one another; changes in elevation

The color green on a topographic map represents ___

forests; thick/heavy tree coverage

index contours

heavy brown contour lines

elevation

height above sea level

northings

horizontal lines that go in a northerly direction ( north-south coordinates)

Smaller number is usually____

latitude

graphic bar scale

like a ruler; note the location of 0

Larger number is usually ___

longitude

east declination

magnetic north is a clockwise rotation from the true North

west declination

magnetic north is a little west of true north and is found by a counterclockwise rotation from true north

quadrangle

map area that is bounded by lines of latitude (North-South) and by lines of longitude (West-East)

gradient

measure of the steepness of a slope gradient= difference in elevation/horizontal distance

bar scales

most obvious scales on a USGS topographic map

The color purple on a topographic map represents ___

new features since map was last updated i.e. If map was made in 1950 and a new store was built after the map was made, the new store would be labeled as purple

true north

north according to the earth's axis, not magnetic north; geographic north pole

principal meridians

north-south lines

representative fraction scale (fractional scale)

numerical scale based on a ratio commonly expressed above the bar scales in the bottom margins of topographic maps

true north, magnetic north, grid north

orientations for the point at the center of a USGS topographic quadrangle map are indicated by 3 lines

central meridian

perpendicular to equator; longitude of origen

equator

plane that is perpendicular to Earth's spin axis and that passes through Earth's center an imaginary line drawn around the earth equally distant from both poles, dividing the earth into northern and southern hemispheres and constituting the parallel of latitude 0°

topographic contours

represent elevations on ground surface; lines connecting points of equal elevation

hachure marks show ___

represents topographic relief; i.e. depressions (appear as "bulls-eye" however like hills and mountains)

meridians

semicircles; lines of longitude

sections

square mile subdivisions

The Rule of V's

streams cause a deflection in contour lines. The contour lines will make a "V" shape as they cross the stream, and the point of V will always point upstream

zones

strips of longitude having a width of 6 degrees

WGS84

the World Geodetic System of 1984 datum (used by the Global Positioning System) (current version of WGS)

mean declination arrows

the angle on the horizontal plane between magnetic north (the direction the north end of a compass needle points, corresponding to the direction of the Earth's magnetic field lines) and true north (the direction along a meridian towards the geographic North Pole). Printed on the bottom margin of a map

magnetic declination

the difference between the magnetic north and the true north

magnetic north

the direction a compass needle points (in the northern hemisphere) in response to the earth's magnetic field. It deviates from true north over time and from place to place because the earth's magnetic poles are not fixed in relation to its axis.

Universal Transverse Mercator (UTM)

the grid system of locating coordinates across the globe; measured in meters

prime meridian

the meridian, designated at 0° longitude, which passes through the center of the Airy Transit Circle Telescope at the Royal Observatory in Greenwich, England.

UTM grid north

the northerly direction indicated by the UTM grid lines on a map

contour interval

the vertical distance between the elevations represented by adjacent contour lines on a map; center of the bottom margin of the map

The color brown on a topographic map represents ___

topography

eastings

vertical lines that go in an easterly direction (east-west coordinates)

The color blue on a topographic map represents ___

water features