UNIVERSITY OF SOUTH ALABAMA
GY 301: Geomorphology
Last Time
A Simple day;
How to draw contour lines
Computer contouring methods
Lecture 4: Topographic Profiles
Contouring
Contour Maps (summary)
When starting….
•163
•155
•174
•102
•135
•170
X •184
•162
•103
•150
•163
•125
•143
•158
•117
•138
•Use pencil
•Light pressure
•Start
at
the
highest elevation
• do one line at a
time
•Proportionality
rule for contour
spacing
•146
•127
•140
•133
▲ 130
•120
™- contour lines connect points of equal elevation
™- steep slopes are shown by closely spaced contour lines
™- gentle slopes are shown by widely spaced contour lines
™-contour lines do not intersect, branch or cross, except in a
vertical or overhanging cliff.
™- when contour lines cross streams they bend upstream; the
contour line forms a 'V' with the apex at the intersection with
the stream, and pointing in an upstream direction (law of the
V’s-mach one). Beware low gradient streams!
™- - closed contours appearing on the map as ellipses or circles
represent hills or knobs.
™- closed contours with hatchures, short lines pointing toward
the center of the closure represent closed depressions.
Chalk Board
CI=20 feet
Computer Contouring
™Several different software options are available (Surfer,
AutoCAD, etc).
™All permit “rapid” contouring and offer nice options (e.g., 3D
colourization of maps
™Most are rather expensive (e.g., AutoCAD), but not always
(e.g., Google Maps)
™Most are not so user friendly (e.g., AutoCAD)…
Today’s Agenda
Another Simple day;
Topographic profiles
Drawing topographic profiles
Vertical exaggeration
http://www.3dfmaps.com/h3.gif
1
Topographic Profiles
Topographic Profiles
™- A topographic profile is a diagram that shows the
change in elevation of the land surface along any given
line.
™- It graphically represents the 'skyline' as viewed from
a distance.
Topographic Profiles
•163
A
18
0
•155
•174
Draw a
topographic
profile from point
A to point B
•135
•162
•184
•170
•102
170
Topographic Profiles
•103
0
•143
•158
100
•150
150
•125
14
0
•146
•127
•133
•140
B
•117
•138
120
16
130
•163
•120
▲ 130
CI=20 feet
Topographic Profiles
Topographic Profiles
A
•170
1
•155
•174
190
•102
Draw a
topographic
profile from point
A to point B
•135
•162
•184
•103
0
•143
•158
100
•150
150
•125
14
0
•138
•146
•127
•140
•133
B
▲ 130
170
160
150
140
130
120
110
100
90
•117
120
16
130
•163
180
Feet
A
80
170
•163
0
•120
Chalk Board
1
2
Miles
3
4
5
Chalk Board
CI=20 feet
2
Vertical Exaggeration
™Most profiles and cross sections have different vertical and
horizontal scales
™This is intentional; it focuses attention on vertical relief….
™…. However, you must calculate and report this vertical
exaggeration on all profiles/cross sections
Vertical Exaggeration
™Most profiles and cross sections have different vertical and
horizontal scales
™This is intentional; it focuses attention on vertical relief….
™…. However, you must calculate and report this vertical
exaggeration on all profiles/cross sections
Vertical Exaggeration = Horizontal distance/Unit
Vertical distance/Unit
Vertical Exaggeration
™Most profiles and cross sections have different vertical and
horizontal scales
™This is intentional; it focuses attention on vertical relief….
™…. However, you must calculate and report this vertical
exaggeration on all profiles/cross sections
Vertical Exaggeration = 1mile/inch
40ft/inch
Vertical Exaggeration
™Most profiles and cross sections have different vertical and
horizontal scales
™This is intentional; it focuses attention on vertical relief….
™…. However, you must calculate and report this vertical
exaggeration on all profiles/cross sections
Vertical Exaggeration = 132 times
Vertical Exaggeration
™Most profiles and cross sections have different vertical and
horizontal scales
™This is intentional; it focuses attention on vertical relief….
™…. However, you must calculate and report this vertical
exaggeration on all profiles/cross sections
Vertical Exaggeration = 1mile/inch =5280ft/inch
40ft/inch
40ft/inch
Upcoming Stuff
Homework
Finish lab 1 (due tomorrow)
Next Lecture:
Alidades and alidade surveying
Friday’s Lab:
Outside: determining elevation differences (Teams Again)
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