||ES 771 Lab Exercise|
IMAGING RADAR OVERVIEW
Students should utilize the textbook (RSE), lecture 7, and other sources in order to answer the following questions and to supply requested information. You may include diagrams or calculations for some answers.
Conventional radar images are black-and-white portrayals of a single microwave band. However,
false-color multispectral radar images can be produced in a manner similar to Landsat composite images. For example, the X, C, and L bands could be color coded as blue, green, and red to produce a false-color composite radar image. In addition, different polarizations can be utilized to make composite images.
- 1. For a typical imaging radar system, how many microwave pulses are transmitted per second? What does the term bandwidth mean?
- 2. What is the ground-range resolution, given a pulse width (duration) of 0.1 microsecond (µs) and a depression angle of 20°? Hint: see RSE p. 301-303. Note: your result should be in the 15-18 m span.
- 3. What factor controls the azimuth resolution in an imaging radar system? What technique is utilized to improve azimuth resolution?
- 4. Radar images are "pictures" of microwave backscatter (reflection) from ground surfaces and objects. Briefly describe the following kinds of radar signatures, and give examples of objects that would create such backscatter.
Image from NASA.
- Corner reflector
- Radar shadow
- Specular reflection
- Strong backscatter
- Weak backscatter
- 5. What is the relationship between depression angle and incidence angle? How does incidence angle affect microwave backscatter?
- 6. Locate a false-color composite radar image. Download the image file. Explain the manner in which the image was produced, describe features that are visible in the image, and give the source for your image.
- 7. Radarsat SAR has a variety of modes of operation. Describe some of the variations that can be selected for image swath, resolution, and incidence angles.
- 8. Describe the orbit characteristics of Radarsat. What advantages does this orbit have?
- 9. What is the cost for a standard full-scene Radarsat image?
- 10. Radarsat has proven particularly valuable for quick-response monitoring of major floods. Locate an example of Radarsat imagery that depicts a major recent flood. Download the image file. Describe the type of image and what it shows about the flood event.
- 11. Discuss the strengths and weaknesses of Radarsat in comparison to SIR-C/X-SAR of the space shuttle for acquiring radar imagery of the world.
- Written answers (1-11).
- Digital image files (bmp, gif, jpg) for #6 and 10.
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ES 771 © J.S. Aber (2012).