LOCATION SYSTEMS AND TOPOGRAPHIC MAPS
I. Latitude and Longitude. Complete exercise on Fig. 1, which asks you to locate various points on the earth
using latitude and longitude. List answers directly on the page containing the exercise.
II. Public Land Surveying System. In the United States, there is another method of locating a position on a map.
According to rules devised by Thomas
Jefferson, and originally set into law by Congress in 1785, public land at that time was subdivided and surveyed
into
townships, which are squares, six miles on a side, with boundaries running north-south and east-west. Townships
are
further subdivided into 36 one-mile-square sections.
Each township is identified by its position within a grid of north-south range lines and east-west township lines.
Townships
run north and south of a reference baseline, while ranges run east and west of a principal meridian, as illustrated
below.
The shaded township is identified as T 2 S, R 3 W.
a
b
c
Complete exercise on Fig. 2 by locating points a, b, & c using township, range and quarter-sections. ASSUME
THAT YOU ARE LOOKING AT SECTION 11. Please read the page before starting the exercise. List answers
directly on the page containing the exercise.
III. Contouring. Complete construction of topographic map using given elevation and 10 foot contour intervals.
IV. TOPOGRAPHIC MAPS:
Topographic maps represent a graphic two-dimensional representation of a three-dimensional surface. Features
found on the map include relief (hills, valleys, mountains, plains, etc.) which is drawn in brown; water features (
lakes, rivers, canal, etc.) which are colored blue; and cultural features (roads, land boundaries) which are colored
black. Typically, a topographic map produced by the USGS covers an area termed a quadrangle. A quadrangle is
bounded by parallels of latitude, which form the northern and southern boundaries, and longitude lines which
bound the western and eastern boundaries. All topographic maps have a scale, although the scale can vary from
map to map. The scale shows the relationship between an object on the map and its true size
A geologist uses topographic maps to make interpretations of features viewed on the map based on the
characteristics of those features.
Scales & Conversions: The scales observed on the map are 1) fractional, 2) graphic, and 3) verbal.
A fractional scale is often called the representative fraction or R.F
Example: R.F = 1:24,000 or 1/24,000
A graphic scale is typically represented by a bar which is subdivided into units and which is shown on the
map.
A verbal scale is developed simply by stating how map distance is related to ground distance. For example,
"one inch equals one mile".
Conversion Example
One inch on a map with an R.F. of 1:24000 equals how many feet?
1 inch = 24,000 inches
12 inches/foot
24,000 inches
1 inch = ------------------12 inches/foot
1 inch = 2,000 feet
Convert the following R.F.
1:24,000 1 inch = ______ feet
1:48,000 1 inch = ______ miles
1:250,000 1 inch = ______ miles
1:1,000,000 1 cm = ______ km
1:31,680 1 inch = ______ miles
1:62,500 1 inch = ______ miles
1:1,000,000 1 inch = ______ miles
Elevation on the map is the vertical distance of a point above sea-level. The difference in elevation between to
topographic features is the relief. The height of a topographic feature is the difference between its elevation and
its base.
SOME CONVERSION FACTORS YOU MAY NEED TO COMPLETE EXERCISE BELOW
1 nautical mile = 1.15 statute miles
1 degree longitude or latitude = 60 nautical miles
1 degree = 60 minutes
1 minute = 60 seconds
Complete the following questions for the quadrangles listed below:
Los Angeles Quadrangle
1. What is the R.F. of the map?
2. 2.5 inches equals how many miles?
3. What are the contour intervals of this map:
4. What are the bounding latitudes?
5. What are the bounding longitudes?
6. Calculate the width in miles of the area covered by map.
7. Calculate the length in miles of the area covered. What is the total area covered by the map?
8. Which quadrangle would you purchase if you wanted the map to the northeast?
9. Use township, range, and section to locate where Cal State L.A was built—it was constructed in the Gravious
School area. Be as accurate as possible. What is the maximum elevation of the future school site?
10. Where is the highest point on the map and what is its elevation?
11. Where is the lowest point on the map and what is its elevation?
12. What is the maximum relief of the map?
13 Find T2S, R13W, S10. What is the topographic feature just west of the center of the section?
14. When was the map first produced? When was it revised.
15. What is the magnetic declination?
Topographic Profiles
1. Construct a topographic profile from Peak 757 radio tower near police academy at Elysian park to X just north
east of words Mt. Washington. Use a scale of 1 in = 100 feet. Use engineering paper with 10 squares per inch.
2. On your profile, label the Los Angeles River, the margins of the Los Angeles River, and the flood plains of the
river. The flood plains are the flat areas adjacent to the river channel. These areas build up with fine grained
sediments due to flooding of the river.
3. What is the vertical exaggeration of your profile?
Vertical Exaggeration. Depending on why you are creating your topographic profile, you may want to
use vertical exaggeration when constructing it. Ideally, you would want to use a vertical scale equal to the
horizontal scale of the map.
Vertical exaggeration simply means that your vertical scale is larger than your horizontal scale. Vertical
exaggeration is often used if you want to discern subtle topographic features or if the profile covers a large
horizontal distance (miles) relative to the relief (feet).
To determine the amount of vertical exaggeration used to construct a profile, simply divide the real-world
units on the horizontal axis by the real-world units on the vertical axis.
If the vertical scale is one 1"=1000’ and the horizontal scale is 1"=2000’, the vertical
exaggeration is 2x (2000’/1000’). If the vertical scale is 1”=100’ and the scale of the map
is 1”= 62,500 inches, then to calculate the vertical exaggeration the units must be the
same.
4. On the flood plain of the river, you discover small bones belonging to dinosaurs next to
triolobite fragments
A. What do you conclude about the association of the two fossil types and the rough
ages of the rocks that were being eroded by the river
5. In another area of the river wall you find that the wall is comprised of flat-lying shales. The
lowermost is green, contains terabratulid brachiopods and trace fossils. A middle shale is
black, laminated, and does not contain any fossils. The uppermost shale is greenish and
contains a redlichiida trilobite.
A. Make a small stratigraphic column—about 3 inches tall and 1 inch wide. Use
appropriate lithologic symbols and color the different units.
B. Use the lineage diagram below to plot the ages of the fossils. Assume the sequence
is comformable
C. What is the age of the lowermost shale _______
D. What is the age of the uppermost shale _______
E. What is the age of the middle shale _________
Per
Paleozoic
Car
Dev
Sil
Ord
Cam
Fossil/Taxa
PreCam
6. What is the likely depositional environment of the shales?
7. Tell me about the environmental conditions present during the deposition of the shales.
8. What happened to the sequence after it was deposited?