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Radar Mapping

Radar Mapping. Electromagnetic EM Radiation. Electric Field & Magnetic Field Perpendicular to direction of propagation Explains light but is absolutely fundamental for radio spectrum. Typical Radar System. A pulse generator that discharges timed pulses of microwave/radio energy

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Radar Mapping

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  1. Radar Mapping

  2. Electromagnetic EM Radiation • Electric Field & Magnetic Field • Perpendicular to direction of propagation • Explains light but is absolutely fundamental for radio spectrum

  3. Typical Radar System • A pulse generator that discharges timed pulses of microwave/radio energy • A transmitter • A duplexer that alternates the signals involved between transmitted and received • A directional antenna that shapes and focuses each pulse into a stream • Receiving Antenna

  4. Radar Bands • Ka Band: Frequency 40,000-26,000 MHz; Wavelength (0.8-1.1 cm) • K Band: 26,500-18,500 MHz; (1.1-1.7 cm) = Weather Radar • X Band: 12,500-8,000 MHz; (2.4-3.8 cm) • C Band: 8,000-4,000 MHz; (3.8-7.5 cm) • L Band: 2,000-1,000 MHz; (15.0-30.0 cm) • P Band: 1,000- 300 MHz; (30.0-100.0 cm) These are all in the Microwave part of the spectrum

  5. About Radar • RADAR = RAdio Detection And Ranging • Typically radar transmitters send and receive 1500 pulses per second • Pulses last about .1 microsecond • Pulses send 100-1000 waves • What a radar actually measures is time (between transmission and reception) • What a radar actually receives when it’s pointed in a certain direction isn’t always in that direction

  6. Some Radar Effects

  7. Some Radar Effects • Bright = rough, Dark = smooth • Metal reflects brightly • Metal corners or edges reflect especially brightly • A truck has same size radar signature as a bomber • Stealth = eliminate sharp edges and conductive materials • Look direction = Illumination on Image

  8. What Determines Radar Echo • Electrical properties of material (Dielectric Constant) • Conductive = High Dielectric Constant = Reflective • Non-conductive = Low Dielectric Constant = Non-Reflective • Roughness • Can’t “see” things smaller than wavelength • Corners are effective for scattering

  9. Some Dielectric Constants • Air: 1 • Teflon: 2 • Glass: 5-10 • Water: 80

  10. Radar Image of ISS

  11. Radar and Optical

  12. Stereoscopic SLAR

  13. Radar Stereoscopy • Although radar images can be viewed to give a 3-dimensional appearance, truephotogrammetry is far more complex than with optical imaging. • It can be done, although when NASA began radar mapping of Venus they didn’t yet have the ability.

  14. Light and Radar

  15. Light and Radar

  16. Light Vs. Radar

  17. How Time = Illusion

  18. Radar Foreshortening • With optical foreshortening, the facing side of a mountain looks normal and the back side looks compressed • With radar foreshortening, the facing side of a mountain looks normal and the back side looks longer • Layover: On steep slopes objects may appear to overlap because they’re the same distance (time) away.

  19. Light vs. Radar

  20. Light vs. Radar

  21. Layover

  22. Radar Foreshortening

  23. Layover and Foreshortening

  24. Underwater Radar?

  25. Sonar View

  26. How Time = Illusion

  27. Sonar Views of Shipwrecks

  28. German Bomber

  29. Polarization • Radar signals are polarized parallel to their transmitting antenna • H (horizontal) polarization = parallel to bottom of plane • When signals scatter, some of the polarization is lost • What we see depends on the orientation of the receiving antenna

  30. Polarization • Imagine a signal from a perfectly horizontal antenna • It bounces off a perfectly flat surface perpendicular to the beam • A receiver parallel to the transmitting antenna will get 100% return • A receiver perpendicular to the transmitting antenna will get 0% return

  31. HV vs. HH

  32. Multiband Color Composite

  33. Alaska Coast

  34. Reflectivity and Penetration, Florida

  35. Reflectivity, Southern California

  36. IR + Radar

  37. Radar Penetration of Sand, Sudan

  38. Ground Penetrating Radar

  39. Optical and Radar Imagery

  40. TOPEX/Poseidon

  41. The Sea Is Not Flat

  42. Pacific Ocean Sea Surface Changes

  43. Sea Surface Radar Mapping

  44. 2004 Tsunami

  45. Global Wind Speed and Wave Heights

  46. Radar Image of Hawaii

  47. Lidar • LIght Detection And Ranging • Uses laser pulses to measure distance • Anything that affects light affects Lidar • Blocked by clouds, smoke, aerosols • Can monitor clouds, smoke, aerosols • Records distance and direction • Depending on processing, can image vegetation canopy or ground

  48. Lidar

  49. Mount St. Helens

  50. Neolithic Mound, Slovakia

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