UNIVERSITY OF SOUTH ALABAMA
GY 301: Geomorphology
Last Time
1. Course Info
2. Introduction to topographic maps
3. Doug’s inability to tell time
Lecture 2: Topographic maps part 2;
Transit Surveys
Topographic Maps
Scale
Know your enemy!
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• At the bottom of the map; two types
Scale (Relational Fraction; Graphical)
Elevation contours (Relative to M.S.L)
Boundary (Latitude & Longitude)
Color (Water bodies, Woodlands, etc.)
Cultural Features (man-made features)
2) Relational Fraction (RF)
1) Graphical
Elevation Contours
• Contour lines (Brown)
Topographic Map Boundaries
• Always consist of
lines of latitude and
longitude
• Contain tick marks
of UTM and SPCS
on the border
– Based on aerial photographs
analyzed stereographically
– Must agree with benchmarks and
spot elevations
– Contour interval: elevation
change between adjacent
contours
– Hachured contours indicate
closed depressions
103 22’ 30’’
103 30’
32 15’
32 15’
7.5’ Topographic
Quadrangle border
(1:24,000)
http://www.jesseshunting.com/images/topo-bench-saddle1.jpg
32 7’ 30’’
103 30’
32 7’ 30’’
103 22’ 30’’
1
Topographic Map Colors
Today’s Agenda
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Brown: topographic contours
Green: Forest and/or wetlands
White:
White cleared areas (i.e. pastures, etc.)
Black: Cultural features (buildings, roads)
Red: Land office grid system (Township
& Range system); Major road systems
• Magenta: Photo-revised areas
• Blue: water bodies
1. Finish introduction to topographic maps
2. Doug’s inability to tell time
Topographic Map Examples
Map Coordinate Systems
• Land Office Grid system (Township & Range)
• Universal Transverse Mercator (UTM)
• State Plane Coordinate System (SPCS)
Land Office Grid System
R2W R1W
R1E
Land Office Grid Example:
6 miles
R2E
T2N
6
5
4
3
7
2
1
12
• Benchmark 212:
– NW ¼, NE ¼, sec.
36, T3S, R3W
T1N
State Capital
18
13
T1S
19
24
T2S
30
25
31
36
36 square
miles
Legal description of location:
NE ¼ , SW ¼, section 22, T2S, R2E
NW
NE
SE
Target location
2
The Pocket Transit (Brunton)
The Pocket Transit (Brunton)
• Used to measure compass directions
• Allows for magnetic declination correction
• Can measure vertical angles with clinometer.
http://wb8.itrademarket.com/
Components of the Pocket Transit
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2.1: magnetic needle
2.2: graduated circle, azimuth or quadrant format
2.3: zero pin for setting magnetic declination
2.4: sighting arm
2.5: peep sight
2.6: mirror
2.7: round (bull’s eye) level
2.8: clinometer scale (degrees and gradient)
2.9: clinometer level
Components of the Pocket Transit
• 2.10: magnetic declination set screw
• 2.11: clinometer adjustment lever
• 2.12: alidade mount
Magnetic Declination
Using the Pocket Transit
• The pocket transit is used to measure either compass
directions (azimuth or bearing), or vertical angles
Declination
in Mobile
is: 1° 14' W
(changing by
0° 6' W/year)
http://www.ngdc.noaa.gov/seg/geomag/jsp/struts/calcDeclination
3
Using the Pocket Transit
• The pocket transit is used to measure either compass
directions (azimuth or bearing), or vertical angles
• An azimuth or bearing is measured by pointing the
sighting arm toward the target while leveling the
round level
Using the Pocket Transit
• The pocket transit is used to measure either compass
directions (azimuth or bearing), or vertical angles
• An azimuth or bearing is measured by pointing the
sighting arm toward the target while leveling the
round level
• The north (usually white) end of the needle will
indicate the azimuth or bearing
Measuring Direction Example
Pace Count Measurement
Pace Count Measurement
Pace Count Measurement
• Pace count is used to measure distance by counting
the number of paces between two points
• Pace count is used to measure distance by counting
the number of paces between two points
• Pace counts typically range between 2.3 and 3.3 feet
per pace
4
Pace Count Measurement
Pace Count Measurement cont.
• Pace count is used to measure distance by counting
the number of paces between two points
• Pace counts typically range between 2.3 and 3.3 feet
per pace
• Combined with a pocket transit the pace count can be
used to map the location of objects or collected
samples
Average pace count (feet/pace) is determined by measuring the
number of paces over at least 200 feet in 20 different trials. The
average in feet per pace is used to calculate the pace count.
Trial
No. Paces
Dist.
P.C.
(PC -Ave)2
i
1
95
200 ft.
2.10
0.0001
2
97
200 ft.
2.06
0.0009
3
95
200 ft.
2.10
0.0001
4
99
200 ft.
2.02
0.0049
5
93
200 ft.
2.15
0.0036
6
96
200 ft.
2.08
0.0001
7
94
200 ft.
2.13
0.0016
8
96
200 ft.
2.08
0.0001
Ave=2.09
n=0.0114
N=8
Pace Count Measurement cont.
• The precision of the pace count should be determined
by calculating the standard deviation and % standard
error
Standard Deviation = n ( PCi – Ave)2
N-1
=
0.0114
8-1
= 0.040
Using the Pace Count Statistics
• A distance between two points measured 75 paces.
What is the distance of the leg, and what is the
accuracy of the estimate?
Distance = No. Paces * Pace Count Average = 75 paces * 2.09 feet per pace
= 157 feet (rounded to nearest foot)
Accuracy = Distance * (Standard Error %)/100 = 157 feet * 3.83%/100 = 6.01 feet
Standard Error % = ( 2 *(S.D.) ) * 100
Ave
= (2*(0.040))*100 = 3.83%
2.09
Pace & Compass Closed Traverse
• A pocket transit and pace count are used to track the
position of sampling locations
Therefore the distance and accuracy = 157 feet ± 6.01 feet
Pace & Compass Closed Traverse
• A pocket transit and pace count are used to track the
position of sampling locations
• Use this method when a 1:24,000 topo. map is not
sufficiently detailed
5
Pace & Compass Closed Traverse
Pace & Compass Closed Traverse
• A pocket transit and pace count are used to track the
position of sampling locations
• Use this method when a 1:24,000 topo. map is not
sufficiently detailed
• The azimuth and pace from the last sample location to
the starting location are taken to “close” the traverse
• A pocket transit and pace count are used to track the
position of sampling locations
• Use this method when a 1:24,000 topo. map is not
sufficiently detailed
• The azimuth and pace from the last sample location to
the starting location are taken to “close” the traverse
• Inevitable errors should be distributed around the
traverse
Distributing Closed Traverse Error
Distributing Closed Traverse Error
• Error is distributed cumulatively through closed
traverse
• Error is distributed cumulatively through closed
traverse
3
2
2
1
1
original
original
Distributing Closed Traverse Error
• Error is distributed cumulatively through closed
traverse
Distributing Closed Traverse Error
• Error is distributed cumulatively through closed
traverse
4
3
4
3
2
7
2
1
original
6
5
1
original
9
8
6
Distributing Closed Traverse Error
Distributing Closed Traverse Error
• Error is distributed cumulatively through closed
traverse
• Error is distributed cumulatively through closed
traverse
5/9 error
vector
4
3
3/9 error
vector
6
7
5
4
3
2
7
5
2
1
original
6
9
8
Total error vector
1
original
corrected
9
8
Total error vector
Upcoming Stuff
Homework
Get supplies ready (first lab Friday)
Next Lecture:
More topographic maps, transits and pacing
Friday’s Lab:
Outside: pacing and scale exercises (hiking shoes, hat, water,
notebook, lab exercise, umbrella)
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