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