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Exercise 1: Maps, Aerial and Satellite photograph Introduction Maps are essentially tables of quantitative information
visually displayed. Their great value lies in the way this visual presentation
enhances and encourages our ability to interpret the complex interplay of the
data they include. Just as it is the cartographer’s job to construct maps that
are as accurate, informational, and attractive as possible, it is the user’s
responsibility to understand the conventions of mapping in order to interpret
and employ the information maps present. Objectives
After completing this exercise, students
will be able to:
1. define and use the terms latitude, longitude, parallels, great circles, verbal scale, bar or graphic scale, fractional scale, geographic north, magnetic north, magnetic declination, topographic map, contour lines, contour interval, gradient, 2. apply the concepts of latitude, longitude, and determine location; 3.
describe the components of a map; Activity 1:
Vocabulary Review Use
the following links to create definitions of the terms listed below. Make sure
that your definitions are presented in complete sentences and are as
comprehensive as possible.
Activity 2:
Concept Reviews Apply the concepts reviewed above by answering the
following questions.
A. Latitude of 90 degrees N B. Latitude of 66 degrees 33 minutes N C. Line of longitude D. Latitude of 23 degrees 27’ N E. Longitude of 0 degrees F. This line divides the earth into the northern and the southern hemisphere
Activity
3:
The concept of scale Scale is expressed on maps in different ways: verbal scale, ratio, representative fraction, and bar scale. Click on the following link; use the information you find there to produce definitions of the following ways of expressing scale.
Topographic Maps
Topographic maps of the United States, which typically employ scales of 1:24,000, 1:62,500, 1:63,360, 1:100,000, and 1:250,000, are published by the United States Geological Survey. Click on this link: U.S.G.S. Topographic maps, and answer questions e through h.
1. Name the volcano portrayed on these three maps. 2. Which of the three maps represents the largest portion of land around this volcano? 3. Which map gives you the most detailed view of the summit of this volcano? 4. What is the verbal scale of a map whose representative fraction is 1:63,360? Activity 4:
Topographic symbols and distance measurements Topographic maps are designed to provide an accurate and detailed picture of the contours of the earth’s surface. Obviously, a set of symbolic conventions is needed to represent a three dimensional landscape on the flat surface of a map. This exercise will introduce you to the basic conventions that will allow you to read topographic maps with ease and accuracy. Click on this link: Topographic map reading, and answer the following questions: a. What is the color used to draw contour lines (or simply contours)? b. What is a contour line? c. Define the contour interval? Click on the following links: Profile, Gradient, and Vertical exaggeration module. Use the information they contain to answer the following questions: d. How can you tell if a slope is steep? e. What is the gradient of a slope? f. When you draw a topographic profile, you seldom keep a vertical scale identical to the horizontal scale. Explain why. Click on the Vertical exaggeration link and drag your mouse on the number listed on the screen to see how vertical exaggeration affects the relief of an image. Stop Here for Week 1 of maps
g. Use the following topographic map to answer questions 1 through 5.
National Geographic Seamless USGS Topographic maps, 43°49’N, 69°37’W, Boothbay, Maine. Activity 5: Topographic profile A topographic profile is a vertical cross-section along a route. In the example given below, a profile was constructed from the foot of Mount St Helens in Washington State (A) to the western rim of its crater (B), down into the crater (C), up to the eastern rim and down to point D. Click on the following link Mount St Helens to see a picture of Mount St Helens taken from E.
EA CA BA A D
A BA CA DA .
A
Elevations are represented in feet
and distances are given in miles. Using the principles demonstrated above, answer the
following questions: a.
Which of the two slopes, A or B, has the steepest gradient. Explain how
you know. (Hint: if in doubt, check this link: Slope
analysis and scroll down to section 10.4) b.
What is the direction of flow of the stream designated with the letter C?
(Hint: look at the V-shape of the contour lines) c.
Using information from this link: Symbols,
draw the symbol for each of these features. 1.
a cave; 2.
an open pit mine; 3.
gravel; 4.
an intermittent stream. d.
On the following lines, draw a topographic profile of the region along
the blue line on the map. Follow the directions given in the following link (Profile). Activity 6:
Types of Public Land Surveys Two
different types of land surveys have been conducted in the United States: the
indiscriminate “metes and bounds,” and the “grid” or “rectangular”
surveys. “Metes and bounds” surveys base their boundaries on physical
features of the landscape such as roads, large rocks, rivers, and trees. The
original 13 colonies used this method to survey the land. Today, the metes and
bound system is used in twenty states (18 eastern states plus Hawaii and Texas). Established
by the Land Ordinance of 1785, a law to encourage the development of the land
west of the original thirteen states, the public land survey system describes
the land according to the “township” and “range” system. Click on the
following links and observe how this system works. Read the information provided
and answer questions the following questions. Township
and range system, Land
distribution, Example
of Indiscriminate Metes and Bounds a.
Name the five eastern states (other than the original 13 colonies) that
use the metes and bounds systems. Click on this link U.S.
map of land survey to find the answer. b.
In the example of indiscriminate metes and bounds, what were the natural
features of the landscape that were used as the boundaries of the lot owned by
Rice Beadles? c.
Define a township. d.
How many acres are in a section? e.
What is a principal meridian? f.
What is a base line? g.
Imagine a group of two townships placed side by side in an east-west
direction. How many miles do you
have to drive to get from the westernmost corner to the easternmost one? How far
is it from the northern boundary to the southern boundary of this block? The
“rectangular” system of township and range is used in the other 30 states.
Observe the following map.
Map
of the Baker Prairie area located in Washington State, at 46°51’N and 123°04’W Using
this map, answer the following questions. h.
What is the area if the blue square in
acres? i.
What is the area of a red square?
What is it called? j.
What is the area of the purple square? k.
What is the area of the yellow rectangle? l.
How would you label the purple square if you follow the rules given in
the following link? Township
and range system Activity 7:
Geographic North versus Magnetic North Maps, as we discovered, use lines of latitude to indicate
the angular distance to the equator and lines of longitude that connect the
poles. Often a north arrow identifies the north direction. However, many people
are confused about the influence of the magnetic field on the use of a compass
to determine north. Let us first define a number of terms that we will need to
resolve this problem. Click on the following link and define the terms. Glossary
Click on the following links and answer questions e through
j. Magnetic
declination on topographic maps Magnetic
declination explained Causes
of changes in declination Over time, declination changes greatly. Click on the
following link and enter the information required: Compute
values of Earth's magnetic field. To search for any particular place in the
United States, enter the zip code in the window frame and click on “Get
Location” button. In the pink frame, type today’s date. Under “Range of
Dates,” enter the start date as 1900; under “Month” enter 1 for January,
and under “day” enter 1. In the
blue frame, the program will enter the latitude and longitude of the zip code
you entered previously. Click the “Compute” button beneath the purple
window. For this exercise, you might want to enter your university location
information or your hometown. Activity 8:
The UTM Grid Topographic maps also show grid lines, spaced every 1000
meters. This grid is based on a map projection of the earth called Universal
Transverse Mercator. The conterminous United States comprises ten UTM zones
labeled 10 (in the West) to 19 (in the northeast). Click on the following link
to observe the UTM zones in the
Conterminous USA. Click on the following link and observe the UTM
Grid Zones of the World. The horizontal grid lines determine North-South position
and the vertical grid lines establish East-West position. Along the southern
edge of a topographic map, we can observe labels for the vertical grid lines:
for example “760000 mE,” which is to be read as “seven hundred sixty
thousand meters East.” Click on the following link The
UTM Grid System and answer the next three questions. Activity 9:
Delineation of a Watershed Every stream receives water from an area that surrounds it.
In the northern part of the map presented below, Union Creek, flows at an
elevation of about 4,275 feet where tributary stream 1 joins it. The drainage
basin of stream 1, also called a watershed, is delineated in red. Upstream from
stream 1 is stream 2, another tributary whose drainage basin is outlined in
blue. At the scale of the topographic map, the limits of the very small drainage
basin of stream 1 measure 1.5 miles.
Tributary stream 2 Tributary stream 1 Drainage Divide Tributary of Union Creek, Washington (46° 56’ N, 121°23’W)
National Geographic, U.S.G.S. seamless map.
The outside limit of a drainage basin is called a drainage
divide. When it rains or snows, the drainage divide separates the precipitation
as shown by the red arrows. Part of the precipitation contributes discharge to
tributary 1 and 2 of the Union Creek, the rest flows south and southeast toward
other streams.
Stream 2 Stream 1 Area south east of Chenalis, Washington State (46°36’N,
122°51’ W) Activity
10: Aerial
Photographs and Satellite Images Powered—and, yet more recently, space—flight has
provided cartographers with an almost unlimited source of photographic
information about the earth’s surface. This exercise will give you a brief
introduction to how aerial photographs and satellite images are produced and
interpreted. Click on the following link: Aerial
Photographs and Satellite Images, and answer the following questions. a.
How does the altitude of the sensor affect the level of detail of an
aerial photograph? b.
Today, color-infrared images are widely used. When were they developed
and why are they employed? c.
Why is natural-color film more rarely used than black-and-white and
color-infrared films? d.
How does the scale of the photograph vary as a function of the altitude
of the sensor? To allow observers to see an image in three dimensions, pairs of
overlapping images, called steropairs, are employed. These photographic pairs,
which overlap by at least 60%, produce a three-dimensional effect when viewed
together through a stereoscope. Some stereopairs are vertical, such as the one
in the following link: Stereopair
of a steep scarp in Colorado in 1982. Others,
typically taken from an airplane or a satellite, are perpendicular or slightly
tilted: Stereopair of
desert scene and Satellites images have been used for monitoring phenomena
related to agriculture, forestry, coastal studies, urban planning, cadastral
mapping (the mapping of land parcel), natural hazards, geology, water, oil and
mineral resources, pollution, cartography, and land use/land cover studies.
Satellites such as SPOT, a satellite capable of producing high resolution images
created by the Centre National d’Etudes Spatiales in France in cooperation
with Belgium and Sweden, have the ability to monitor the same area of Earth
every day. SPOT satellites revisit the same location every twenty-six days. Note
that the smallest objects that can be identified images are the size of a pixel,
which on SPOT images varies from 10 to 20 meters. This is called the resolution
of these images. A good example of SPOT monitoring can be seen by clicking
on the following link: Spot.
Access the “photo of the month” (upper right pull down menu) that shows the
Mekong flooding in 2000. Move your mouse over the dates to see a series of five
photographs, taken from June 12th to September 25th, 2000.
These photographs were taken using a color infrared film.
Healthy vegetation is red; silty water is light blue.
A full size image will appear on your screen if you click on the date on
the right hand side of the photograph. e.
Name two manmade features visible on the image. Explain what helped you
in recognizing each feature. In 2002, Spot
5 was launched and will produce images with an increased resolution: 2.5 meters
in black and white and 10 meters in colors. Click on the following links: Spot
5 and Canadian
Tutoring. Answer the following questions. f.
What is the altitude of a Spot satellite orbit? g.
Define the term “revisit period.” h.
Why is the revisit period shorter in higher latitudes than at the
equator? Among the other satellites that have immensely contributed
to our understanding of the Earth and the monitoring of its surface are the
Landsat satellites series. The pixel size is greater (79 meters x 79 meters)
than the SPOT. The swath of the SPOT satellite varies between 60 and 80
kilometers; the swath of the Landsat satellites is 185 km. The newest satellite
of the Landsat series, Landsat 7, has an orbit altitude of 705 kilometers, a
revisit time of 16 days, and a ground resolution of 30 meters in color and 15
meters in black and white, a substantial improvement over the older members of
the series. i.
Is the resolution of a Landsat satellite color image greater or smaller
than the resolution of a SPOT satellite? j.
What is a swath? k.
Explain why the revisit time for Landsat is shorter than the revisit time
of SPOT. |
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