LAB 2: AERIAL PHOTOGRAPHY AND PHOTOGRAMMETRY PART 1: INTERPRETATION OF AERIAL PHOTOGRAPHY

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1 E&ES 328 Remote Sensing Laboratory LAB 2: AERIAL PHOTOGRAPHY AND PHOTOGRAMMETRY Due February 22, 2012 PART 1: INTERPRETATION OF AERIAL PHOTOGRAPHY Some of the first aerial photography, employed during World War I. The purpose of this lab is to introduce you to techniques to identify objects in a scene and familiarize yourself with geomorphic features in plan view. Use the stereoscopes if available. Supplementary reading: Process Geomorphology Ritter et al. Atlas of Landforms 3 rd ed. Curran et al. IMAGE ANALYSIS When preparing to analyze remotely sensed data, it is important to note the basic details of the image. While I will try to provide this information for each image in the lab, this information is not always available and you will have to use your knowledge of geological and manmade features to infer the scale. Basic parameters include: 1

2 Scale. Knowledge of the size of objects is critical for interpretation. Manmade features such as roads, cars, houses serve well as indications of scale. Geomorphic features such as drainage pattern and density, crater type may also yield information. Direction of incident radiation. In the absence of a topographic map or stereo image, this is critical to identifying the direction and magnitude of relief. Location. Is the region typically arid, cold, etc.? Time of year. Vegetation and snow may cause a landscape to look different at different times of year. Look for indications of ice in waterways if snow is not apparent on the ground. IR photography greatly facilitates identification of vegetation. Tone, Color, Texture. Here it is important to rely on your experience to interpret variations in these parameters. Trees often appear rough at visible wavelengths. Pattern. Drainage patterns give information about rock type below. For each description utilize these parameters in order to make your interpretation. Unless otherwise noted, N is at the top of the image. LANDFORMS Igneous Landforms Grand Canyon, Arizona 17A, B Wow! This is what stereo is for! This is a portion of the western Grand Canyon. Examine the surface north of the canyon. Fluvial Features 1. What is the dark unit? How do you know? Speculate as to how the dark unit may have affected the river flow. Indiana 2-B, 2-C, Alaska 68a and 68b Structural Features 2. What are the landforms seen in these images? 3. How are floodplains built? Kansas 2-A and B N, W 1:20,000 September 18, 1937 This region is dominated by Permian age cherty limestone and shale. 2

3 4. Can you identify each of these in the images? What is the attitude of beds in this region? What type of land cover is this (forest, plains, etc)? How did you make this determination? Arkansas, 1-A and 1-B 5. What is this feature? Did it form in the brittle or ductile portion of the lithosphere? Carrizo Plain, CA 6A and 6B A very famous structure trends NW-SE across this image. Glacial Landforms 6. What is this structure? 7. Describe any indicators of the direction of movement along this structure. What is the direction of movement? Rochester, NY, 15A & 15B 8. What are the landforms seen here? Hint: The landforms also exist out the window (Indian Hill Cemetery). Antarctica 10 February 16, 1960 Aeolian Landforms 9. What is the scale of the image (measure it)? With this knowledge, speculate as to the nature of the black specs on the surface. California 39A, B N, W 1:20,000 November 10, 1959 This area, near the Salton Sea, has geomorphic indicators of direction. Color Infrared Film 10. What is the direction of prevailing winds in the region? How do you know? Color infrared film records green (blue on the film), red (green on the film) and infrared (red on the film) light. Refer to your text, page for further discussion. As vegetation reflects strongly in the infrared, red regions on the image contain vegetation. 3

4 Connecticut IR, 1973 Examine the infrared image (note the specular reflection on the water of the Connecticut River). 11. What accounts for the variation red color in the image? In which season you think this image was taken? PART 2: PHOTOGRAMMETRY AND ANALYSIS OF STEREO IMAGES Tools Needed: Ruler, Calculator, Textbook Figs. 6-11, 6-18, 6-20, In this lab, you will practice the art and science of photogrammetry by examining stereo image pairs with stereoscopes. Common methods you will utilize include: Location of the Principal Point (PP). The principal point is determined by the intersection of lines drawn between fiducial marks. TAKE CARE NOT TO DRAW ON THE PHOTOS! Use transparent overlays as needed. Location of the Conjugate Principal Point (CPP). The CPP is the location of the principal point of one of the images on the other image. Determination of Air Base. The distance between successive principal points. Scale. The average scale of a photo, s = f/h, where f is the focal length of the photo and H is the flying height. Note that the units need to be the same in the calculation. The Parallax Equation The difference between the absolute parallax of the top of an object and the bottom of an object is the differential parallax, dp. This can be inserted into the parallax equation: h o =(H-h) * dp/(p+dp) where h o = height of object H = flying height of aircraft h = altitude of scene above the datum (H-h) = flying height above the ground. P = air base of photos Parallax can be determined by a number of methods: 4

5 Parallax Determination Using Fiducial Marks (Fig. 6-21a,b) Measurement of the distance of the top and bottom of the object of interest from the fiducial line gives the parallax of the object in a stereo pair. Photos 2163, 3-16 & 3-17 Tanker Docking Area. These photos provide a good example of relief displacement. The flying height is 300 m, focal length is 15 cm. 12. Determine the height of the Hess fuel tank. Parallax Determination Using Superposition (Fig. 6-20) Orient the stereopair so the top and bottom of the object of interest is parallel to the line of flight. The differential parallax can be calculated from the difference between the distance of the top of the object in the two photos and the bottom of the object in the two photos. Use this method to recalculate the height of the Hess tank. 13. The quickness of this method allows you to calculate the height of another oil tank. Do so and verify that the second oil tank appears visually higher or lower than the Hess oil tank as your calculations suggest. Indicate which oil tank you measured by drawing a sketch map. Black Mesa, Arizona, 9A & 9B This is a spectacular image of the north rim of Black Mesa Canyon. Here sandstone caps a series of shales (some of which contribute to dark rock slides visible in the canyon). 14. Select a few points and determine an average height of the canyon. Middletown, CT 2837, 2838, March 9, 1970 These images of Middletown were taken in 1970, but the height of the plane is unknown. We will measure the height of the Science Tower using trigonometry outside. 15. Measure the P and dp on the images of the Science Tower. Use the known height to calculate the height of the aircraft that took this picture. 5