3. Topographic Maps
• A topographic map, also known as a
contour map, is a map that shows the
shape of the land using contour line.
• Contour lines are lines that connect points
that are of the same elevation.
• They show the exact elevation, the shape
of the land, and the steepness of the
land’s slope.
• Contour lines never touch or cross
eachother.
22. Topographic Maps
• Contour Line –
- line on a map that connects points of EQUAL elevation.
- show elevation and shape of the land
• Relief – Difference between high and low elevations
23.
24. Topographic Maps
• Contour Interval –
difference in elevation
between each line.
MUST be equal
spacing.
Contour interval =
20 feet
520
540
560
580
25. Topographic Maps
• Index Contour –
Usually every 5th line is printed darker and has
an elevation printed on it.
29. Rules for Contours
3. Contours bend upstream (uphill) when
crossing a stream.
Contour lines form V’s
that point upstream
when they cross a
stream
It is important to
remember that they
point in the opposite
direction as the flow
of water
30.
31. Rules for Contours
4. The maximum possible
elevation for a hill is “1”
less than what the next
contour “should” be.
The highest possible
elevation of the hill is
just below the value
of the next line that is
not shown
50
60
70
80
90
38. Depressions
• Contour lines which show a depression,
crater, or sinkhole on a map.
• Shown by dashed lines (hachure marks)
on the inside of a contour line
40. Rules for Contours
The lowest possible
elevation for a
depression is “1” more
than what the next
contour “should” be.
The lowest possible
elevation of a
depression is just
above the value of the
next line that is not
shown
50
90 90
80
70
60
51
41. Benchmarks
• a location whose
exact elevation is
known and is noted
on a brass or
aluminum plate.
• bench marks are
shown on maps by an
X with the letters BM
written next to them.
42.
43. Map Scales
• The relationship between distance as
measured on a map and the actual distance
on Earth’s surface
44. Types of Map Scales
a. Verbal Scale – 1 inch = 20 miles
b. Bar Scale
One Mile
45. Types of Map Scales
c. Ratio Scale -
One of any unit on this map represents
24,000 of the same unit on Earth’ s surface.
Ex, one inch would equal 24,000 inches on
the Earth
46. • Maps often give you more than one way to
measure distance
Represents one
mile on the map
Represents parts of
one mile, ex: one tenth
of a mile
One kilometer
47.
48. Gradient
• The slope between any two points on a hill
• Gradient =
Change in Field Value
Distance
49. Gradient
• A trail is four miles long as measured by
the scale on a map. The beginning of the
trail is at the 1,060 ft contour line and the
end of the trail is at the 960 ft contour line.
Calculate the gradient of the trail.
Gradient = =
1060 ft – 960 ft
4 miles
25.0 ft/mi
50. 1- What A, B and C stands for ?
2- What is the gradient of XY while the distance between XY is 200M
