Topographic maps translate terrain and relief onto planimetric maps
GEOG3710
Lecture 3:
Terrain interpretation with maps
Dr. Hester Jiskoot
Contouring:
Interval/spacing/interpolation/V-rule
Shading:
Colouring:
Mt. Rainier, US
DEM
Overlay choropleth map onto contours
MAPPING TERMINOLOGY
Contour lines
Lines connecting points of equal elevation above mean sea level so that relief features are
profiled into a 3D perspective.
Elevation
Vertical distance from a datum (usually mean sea level) to a point or object on the earth's
surface.
Relief
The physical configuration of the earth's surface, depicted by contour lines and spot
heights.
Topography
Surface features both natural and cultural, collectively depicted on topographic maps.
Spot elevation
A point on a map where height above mean sea level is noted, usually by a dot and elevation
value; shown where practical (road intersections, summits, lakes, large flat areas,
depressions).
Vertical datum
The reference or basis for elevations (usually mean sea level).
Contour maps 1-3
Projection
Geometric representation of the curved surface of the earth on a flat sheet of paper.
Universal Transverse Mercator (UTM) grid
A square grid system based on the Transverse Mercator projection, depicted on maps. It can
be used to accurately locate the position of features on the map by distance or direction.
Units, index contours, and contour intervals
V-RULE FOR CONTOURS
• River flows in which direction?
• What are the elevations of contour lines A,B and C?
GEOMORPHOLOGIC TERMINOLOGY
Peak/Summit: Point that is higher than all adjacent points:
local maximum elevation
Depression: A low place in the ground having no outlet for
surface drainage.
Hachures: Sets of short nearly-parallel lines used in map
making to represent a sloping surface. A depression/pit
has a circular contour line with hachures on the inside.
Hill: A naturally occurring mass of earth material whose
crest or summit is at a lower elevation than a mountain.
Mesa: A flat-topped mountain with steep sides.
Ridge: A long narrow elevation of land (also Arrête); a steep
slope or a similar range of hills or mountains.
Saddle/Col: A depression or pass in a ridgeline.
Valley: A stretch of low land lying between hills or mountains:
valleys are sometimes occupied by a stream.
http://www.nrcan.gc.ca/earth-sciences/geographyboundary/mapping/topographic-mapping/10131
TRANSECTS:
Transverse or Cross
Longitudinal
Map distance ≠ Ground distance
SLOPE
Transects?
Rise = vertical distance
Run = horizontal distance
PERCENTAGE
Formula: (Rise/Run)*100
Examples: (100/2300)*100=4.3%
(100/400)*100=25%
RATIO OR GRADIENT
100/2300=1/23
100/400=1/4
DEGREE
Formula: arctan(Rise/Run) (=tan-1(Rise/Run)
Arctan(100/100)=45º
Arctan(100/2300)=2.49º
Arctan(100/400)=14.04º
ORIENTATION
Degrees or cardinal direction the slope is facing
Topography reflects geology
Smoke holes, West Virginia
READING MAPS
Geographic and UTM reference coordinates on the same map
LOST:
Title/Type, scale, projection, magnetic declination, Coordinate system, legend
TOPOGRAPHIC INFORMATION:
Overall relief
Orientation landforms
Character terrain Æ f(Geology)
Which landmarks are visible from different points
Interpretation surface processes
EXAMPLES
LANDSCAPE ANALYSIS
Resulting from exogenic and endogenic forces
Look at:
SHAPE
Rolling hills
Æ look at: shape, size, height,
direction, concentration, composition
Incised streams
Æ look at: flow direction, signs for
former flow, sediments, geology
Sediment influx
Æ look at: composition, texture,
structure
Erratics
Æ look at: rock type, position in
landscape, ‘trains’
Recent activity
Æ look at: mass movement, recent
gullies, changing sediment load
DIMENSIONS
PATTERNS
STRUCTURE
COMPOSITION
DISTRIBUTION/SETTING
ANTHROPOGENIC CLUES
Æ look at:
Building stones
READING FOR FRIDAY
Cemeteries/gravestones
Vision quests and sun dials
Place names
Location of roads
Partitioning of land
p.29-34
Æ Keeping a field book
p. 23-28 Æ Procedures for taking weather
observations
p. 54-58 Æ measuring slopes with the
clinometer on the compass
St Alban’s ‘English’ Church, Copenhagen
Vision quest rock, Milk River region, AB
What to bring on Monday and where do we meet?
Bring:
Field book
Pencil
Compass with clinometre
Lab instructions (p. 6 reader)
Pace ruler
Ruler and/or protractor
Sturdy shoes & proper clothes
Water and snacks
Meet:
13:00 at the Greenhouse, N-side of the UHall level 6