LAB 5: Imagery: Stereoscopes & Surveyinghomepage.smc.edu/patrich_jeremy/Labs/Physical Geography...

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Patrich Physical Geography Lab | 1

LAB 5: Imagery: Stereoscopes & Surveying

Previoulsy you worked briefly with topographic maps and Google, this lab will revisit some of the topographic fundamentals; along with providing you the tools on how to make your own map with actual data collected in the field. This lab will also have you evaluate some stereoscopic imagery. It is strongly encouraged that a reconnaissance visit to the project site is made prior to the performance of any fieldwork. This initial visit will allow you to become familiar with the site, identify any access issues. It will also provide you with an opportunity to assess the amount of vegetation onsite, which may present difficulties during your survey work. Your initial assessment of the site will better allow you to estimate how much time will be required to complete the desired fieldwork. Below is an image of the area in which we will be working with. Please describe what you see- features, environment, size, etc. 1.


Stereoscopic Imagery Stereoscopic viewing is achieved by simultaneously viewing the same tract of land as it appears on two photographs taken from different camera positions. A stereoscope reproduces the same parallax-dependent sense of depth by allowing us to view one photograph with the left eye while viewing another spatially displaced photograph with the right eye. This technique successfully tricks the brain into thinking that the parallax displacement apparent in the merged images of the two adjacent photographs is the result of viewing a truly three-dimensional surface through unaided eyes. Consequently, stereoscopic viewing allows us to see the area photographed in three dimensions; it is a very powerful analytical technique that is an important part of the geographer's 'tools of trade' Proper Use of Stereoscopes: The following are some guidelines that will help you use your stereoscopes properly. They are important and should be kept in mind when performing stereo based interpretations: 1. Be sure that the photos are properly

aligned, preferably with the shadows toward the viewer. (Having the shadows away from the viewer can cause terrain reversal or “false stereo”.)

2. Be sure to keep the eye base and the long axis of the stereoscope parallel to the flight line.

3. Try to maintain an even glare free illumination of the images and make you are comfortable.

4. Keep the lenses of your stereoscope

clean.


Stereoscopic Images of Yosemite


Stereoscopic Images of The Grand Canyon


Stereoscopes Continued: The instructor will provide you a stereogram atlas with images from around the nation. This part of the assignment will require you to pick 3 different images and to research them.

1. Pick an image and view it using the provided stereoscopes 2. The answer the questions provided. Be sure to use the information in the book

as well as any information you found using your smartphone/laptop Image 1: Page # _______ Name of Photo ________________________________________________________

a. Where is this feature located?

b. What is it that you are observing?

c. How was this feature formed?

d. What is something interesting you have observed in this image? Image 2: Page # _______ Name of Photo ________________________________________________________




d. What is something interesting you have observed in this image? Image 3: Page # _______ Name of Photo ________________________________________________________




d. What is something interesting you have observed in this image?


Connecting the Dots Once data is collected and plotted, making a map is similar to connect the dots. Below is a sample diagram of elevations, some odd, some even. It is your job to connect the dots. Sometimes you will find that there may not be enough of the numbers you are looking for- that is where you have to figure out where that number belongs.

First- Dot the spot where the number belongs. The more dots you place, the better the accuracy of your map. Second- Connect the dots of like elevation.

Below I have completed the 40ft contour, you need to next connect the dots. You will then repeat those steps for the following contour lines: 35, 30, 25, 20, 15, and 10.


How to Use an Auto Level Terms:

• Backsight: A point of known elevation and location. Otherwise known as a BS, a backsight is recognized as a benchmark.

• Foresight: A point with no known elevation. Otherwise known as FS.

• Height of Instrument: The

height of the Auto Level—found after the rod is placed on a BM, then adding the height read from the rod to the known elevation. Otherwise known as HI.

• Bearing: Degrees read from compass. EG 136*


Math Notes & Practice PS. Check your math. BS values between the horizontal plane & stadia are always equal! Formulae:

• HI=BM+BS • Distance=(Stadia A – Stadia B) x 100 • Elevation= HI-FS


How to Make a Map The next step in surveying—is putting it together as a map. With the data, we have a permanent station, the distance and direction of each ‘shot’, and plotting this data as a map simply requires the use of a paper, protractor, ruler and pencil. The data collected represents the perimeter of a sand sheet, (that is why the elevations are so constant). For this activity, the cartographer decided that it would be best to convert the data as: 1 cm=2 meters. This will be helpful so that out map will not exceed that of the paper we are drawing on. I have completed stations 1, 4, 8 and 16. Your job is to complete the remaining stations—and then to ‘connect the dots’. Your final map will show the perimeter of a sand sheet within the Keeler dune complex, in Owens Valley.


Station Back Sight

HI Height of Instrument

Foresight Distance M Elevation M Bearing Remarks

5.66 BM=Reference 5.32 944.00 68 938.68

4.983.03

1 2.93 20 942 99*2.833.16

2 3.05 22 942 107*2.943.29

3 3.17 24 942 111*3.053.32

4 3.21 22 942 117*3.103.38

5 3.25 26 942 137*3.123.03

6 3.91 24 942 142*2.793.12

7 3.00 24 942 145*2.883.80

8 3.65 30 942 147*3.503.71

9 3.53 36 942 152*3.353.82

10 3.62 40 942 154*3.423.26

11 3.06 40 942 158*2.863.62

12 3.42 40 942 159*3.223.51

13 3.29 44 942 160*3.073.28

14 3.04 48 942 161*2.803.37

15 3.15 44 942 163*2.933.32

16 3.09 46 942 165*2.86


Station Back SightHI Height of Instrument Foresight Distance M Elevation M Bearing Remarks

5.66 BM=Reference 5.32 944.00 68 938.68

4.983.20

17 3.09 22 944 99*2.983.16

18 3.04 24 944 107*2.923.29

19 3.16 26 944 111*3.033.32

20 3.19 24 944 117*3.083.38

21 3.24 28 944 137*3.103.03

22 2.90 26 944 142*2.773.12

23 2.99 26 944 145*2.863.80

24 3.64 32 944 147*3.483.71

25 3.52 38 944 152*3.333.82

26 3.61 42 944 154*3.403.26

27 3.05 42 944 158*2.843.62

28 3.41 42 944 159*3.203.51

29 3.28 46 944 160*3.053.28

30 3.03 50 944 161*2.783.37

31 3.14 46 944 163*2.913.32

32 3.08 48 944 165*2.84


Place center of protractor here

1cm

= 2

met

ers

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LAB 5: Imagery: Stereoscopes & Surveyinghomepage.smc.edu/patrich_jeremy/Labs/Physical Geography...

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