Name: ______________________________
Lab 4: Plane Table Mapping and Topographic profile
MATERIALS NEEDED:
-a ruler
-a lap board (provided by instructor)
-a large piece of paper (provided by instructor)
-a pencil with eraser
-a 50 m measuring tape (provided by instructor)
-a compass (provided by instructor)
-a protractor (provided by instructor)
QUESTION 1: RELATE TOPOGRAPHIC MAP TO FIELD FEATURES
Connect to the following web site: http://topozone.com/find.asp
PART A: OBTAINING A TOPOGRAPHIC MAP FROM THE WEB
STEP 1: Display a topographic map for the city of Indianapolis.
1. Using the map displayed on the computer screen, describe the changes you observe as you modify the scale from 1:25,000 to 1:100,000.
2. What do the changes you just observed tell you about map scale?
STEP 2: Locate the White River and IUPUI campus on the Indianapolis-West topographic maps handed out in class.
1. Along what general direction is White River oriented between New York Street and 10th Street? Record your answer both as a bearing (point of a compass) and an azimuth (see Lab 3).
2. What is the average elevation gradient from the corner of 10th Street and University Boulevard (just by the YMCA) and the East bank of White River under the bridge across New York Street:
(Show all your calculations)
a) In m per km?
b) In ft per mi?
PART B: RELATING THE 2D FEATURES ON YOUR TOPOGRAPHIC MAP TO FIELD SETTINGS
STEP 1: Using the maps of the IUPUI campus provided, identify the buildings and the major streets of the IUPUI campus shown on the Indy-West topographic maps.
STEP 2: Take a walk down University Boulevard (heading South) until you reach the North bank of the White River. As you walk along, pay attention to the changes in topography.
1. Describe how the changes in topography you have observed along your walk are related to the pattern of contours that are shown on your topographic map.
QUESTION 2: PLANE TABLE MAPPING
Produce a plane table map of the Lecture Hall courtyard. The objects you will map are the Lecture Hall, Education building, University College, and the Business/SPEA building.
PART A: GATHERING THE DATA FOR THE MAP
1. You must work as a team for this assignment.
2. Before you leave the classroom, draw a straight line in the center of your sheet of paper. It should be an even number of centimeters long (5 or 10 cm works well). This line is called your baseline. To keep things oriented the right way once you start mapping, label one end of the baseline 'A' the other 'B'.
3. Your instructor will assign you a baseline in the field from which your map will be constructed. Proceed to one end of it. This will be point A (coinciding with point A as you marked it on your baseline). The point at the far end of the baseline will be referred to as point B. The ground distance between the two points will be measured using the tape provided (50 m works well). Record the distance and units next to the baseline you have drawn on the piece of paper. This will allow you to calculate the scale of the map.
4. Center your mapping surface over one end of your baseline (point A at which you are standing) and orient the paper so that the line you have drawn runs directly toward the opposite end of the baseline: point B.
NOTE: It is essential that your mapping surface does not move until you have plotted all objects.
5. Using a compass determine the azimuth (angle) from the point where you are standing (A) to the opposite end of the baseline (B). Write this azimuth on the map. This will provide the basis for drawing a north arrow on the map.
6. Take your ruler and draw straight lines (known as intersecting rays) extending from the end of the baseline where you are standing toward the objects you are mapping (the corners of each building listed above). Make sure you sight carefully onto each object: small errors can result in large errors on the final map.
NOTE: Label your lines as you draw them so that you know which line goes to which object.
7. Pick up your mapping surface and proceed to the opposite end of the baseline (point B).
8. Place your mapping surface over point B and orient the line to point A.
9. Using your ruler and pencil, draw straight lines (rays) out from point B to the same objects that you sighted on above (the corners of the buildings). The intersection of the rays will mark the location of the objects being mapped. Make sure that the lines will intersect if you close them on your field map. Also, make sure that the positions of the buildings in relation to each other make sense. If their location seems distorted, this is because you have moved the piece of paper while you where mapping.
10. Use a compass to determine the azimuth from point B to point A (this is a check). Write this azimuth next to the corresponding point on your map.
PART B: COMPLETION OF THE MAP
1. On returning to the classroom, trace the intersection rays and the baseline that you constructed. Extend the intersection rays if necessary so that they intersect. Write the name of each building along the line joining the two points of intersection encompassing the building.
2. Calculate the scale of the map by determining what 1 cm represents in reality. This can be achieved using the known distance of the baseline (you measured this in the field) and the corresponding distance on the map. Your scale is the ratio of these two distances.
i.e., if your baseline is 400 feet long in reality and is represented by 4 inches on your paper
400/4= 100 feet per inch which is the same at 1200 inches (100 ft x 12) per inch or a scale of 1:1200
3. Draw a north arrow on your map using a protractor and the compass measurements you made of the orientation of your baseline. Don’t forget that this is the magnetic North. You need to also draw the geographic North (and thus the declination). See Lab 3 for the declination.
Your final map should have:
- Title
- North arrow - both magnetic north and true north
(a
topographic map of Indianapolis is provided to help here)
- Graphic scale bar
- RF scale (Representative Fraction)
- Names of all objects mapped
- Names of all group members in upper right hand corner
4. If there are obvious errors on your map, note them and explain the most likely sources of error.
QUESTION 3: TOPOGRAPHIC CHANGES ASSOCIATED WITH VOLCANIC ACTIVITY
Mt. St. Helens began erupting in March 1980 and continued to erupt regularly until Mid October of that year. The main eruption occurred on Sunday, May 18th, 1980 at 8:32 a.m.
This eruption blew out 3 km3 of the mountain, creating a large crater on the north side. An earthquake of magnitude 5 on the Richter scale accompanied the eruption. Pyroclastic flows of hot gas, ash and pumice heated up to 870°C (1600°F) flowed down the slopes at speeds up to 1600 km h-1 (1000 m.p.h.), destroying vegetation and wildlife. Accompanying this heated flow were avalanches, landslides, and debris flows. These flows extended in an arc of 16-25 km (10-16 miles) from the north side of the volcano. The volcano also ejected large chunks of rock that traveled several km away from the volcano.
The heat from the eruption melted snow and glaciers on the volcano, creating avalanches and heated mudflows that blocked streams to the north and west. New lakes formed as water from blocked streams and melting glaciers collected behind the natural earthen dams. Lighter material from the eruption was ejected up to 20 km (14 miles) in the atmosphere. Clouds of ash blew to the NE, reducing the amount of incoming solar radiation reaching the surface. Some of the ash settled in the western US and Canada. Four days later, ash reached the east coat of the U.S. Ash was then distributed worldwide by the circulation of the atmosphere.
1. Plot a topographic profile along the section A-A' across the volcano ( before the eruptions: i.e., Map 1- April 1980) and along the section B-B’ (after the eruptions: Map 2 - March 1981).
NOTE: You will have to interpolate the elevation for some of the end points of your profiles, unless a contour line is crossing each of them.
Draw both profiles on the same graph (on top of each other).
Use a vertical exaggeration of 6x. You can refer to Lab 3 to refresh your memory on this topic.
Clearly label which profile is which (before and after eruptions).
Mark the summit (highest point along your profile) and crater of Mt. St. Helens on both your profiles.
Label the axes and report the vertical exaggeration (show your calculations below).
2. What was the change in elevation between the pre-eruption summit and the new post-eruption summit?
3. What was the change in the gradient of the north side of the volcano as a consequence of the eruption? (Use the point labeled with an "X" as the highest point from which you calculate the gradient on both profiles).
HINT: to assess a change in gradient, you have to calculate both gradients (before and after the eruption).
4. a) What happened to Spirit Lake in terms of its size?
b) By how much (approximately) did its elevation change?
HINT: Look at the contours.
c) Why do you think this happened?
HINT: refer to the text presented at the beginning of this section to answer.
5. What is the representative fraction (RF) of the Mt. St. Helens map?
