Lecture 17- Topographic Maps Part 1 Flashcards
What is a topographic map?
A 2-dimensional representation of a 3-dimensional land surface (Landscape)
What are contour lines?
Lines of equal elevation (above sea level) on a topographic map. They indicate height or elevation on a topographic map. Each point on contour line has same elevation
Contour lines enable us to show?
-Landforms (hills, valleys, slopes, coastlines)
-Relief (differences in elevation)
Most topographic maps depict a:
Quadrangle
What is a quadrangle?
Section of Earth’s surface bounded by lines of LATITUDE (at top or north and bottom or south) and lines of longitude (at left/west and right/east)
North always at top of:
quadrangle and represents direction of true north, abbreviated GN (grid or geographic North Pole)
Magnetic compasses are attracted to:
Magnetic North Pole or COMPASS NORTH (abbreviated MN) and NOT TRUE NORTH
Some topographic maps present compass-like symbol. This symbol shows and is:
Declination: difference in degrees between compass north (MN) and True North (GN).
Magnetic/compass north migrates and therefore declination at specific site changes over time
Topographic maps are constructed by:
viewing a specific area directly from above
TOPOGRAPHIC MAPS constructed by viewing a
specific area directly from above.
This ensures what:
Contour lines are not hidden behind a feature such as a hill or mountain
Topographic maps?
Miniature models of Earth’s 3-dimensional surface on a 2-dimensional piece of paper or screen
How is elevation expressed
Using contour lines
True or false: elevation are written on each contour lines
False
Index contour lines:
Contour lines that are drawn thicker and have ELEVATION printed on them
What do index contour lines do (2)
-Labelled with elevations that consistently increase or decrease by same amount/increment
-enable reader to determine contour interval
Contour interval:
-Increase or decrease in elevation between any two contour lines
-Remains constant for any given contour map
Contour interval equation
=Elevation change/number of contour lines
Ex: 100 unites/ 3 contour lines= 100 units
Can fill in elevation at each contour line
What is elevation at sea level
0 Unites
Convex versus concave cliffs:
Concave: Contour lines will be closer at higher elevations and further apart at lower elevation
Convex: Contour lines are further apart at higher elevations and closer together and lower elevations.
What is a depression?
A landform sunken or depressed below surrounding area, has lower elevation that the surrounding area. Contour lines have Hachure marks on the downhill side
Contour lines form a V pattern when:
Crossing streams or rivers or creeks
What is the APEX
The pointy end of the V will always point upstream towards o source of water/towards higher elevations.
Water flows from:
Higher elevation to lower elevation
A ridge and valley have
Contour lines occurring on opposite sides of a valley or ridge always occurring in pairs. The contour lines with equivalent elevations are found on both sides of valley or ridge.
