radar mapping
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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 System1. A pulse generator that discharges timed
pulses of microwave/radio energy
2. A transmitter
3. A duplexer that alternates the signals involved between transmitted and received
4. A directional antenna that shapes and focuses each pulse into a stream
5. Receiving Antenna
Radar Bands
1. Ka Band: Frequency 40,000-26,000 MHz; Wavelength (0.8-1.1 cm)
2. K Band: 26,500-18,500 MHz; (1.1-1.7 cm) = Weather Radar
3. X Band: 12,500-8,000 MHz; (2.4-3.8 cm)4. C Band: 8,000-4,000 MHz; (3.8-7.5 cm)5. L Band: 2,000-1,000 MHz; (15.0-30.0 cm)6. P Band: 1,000- 300 MHz; (30.0-100.0 cm)These are all in the Microwave part of the
spectrum
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
Some Radar Effects
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
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
Some Dielectric Constants
• Air: 1
• Teflon: 2
• Glass: 5-10
• Water: 80
Radar Image of ISS
Radar and Optical
Stereoscopic SLAR
Radar Stereoscopy
• Although radar images can be viewed to give a 3-dimensional appearance, true photogrammetry 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.
Light and Radar
Light and Radar
Light Vs. Radar
How Time = Illusion
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.
Light vs. Radar
Light vs. Radar
Layover
Radar Foreshortening
Layover and Foreshortening
Underwater Radar?
Sonar View
How Time = Illusion
Sonar Views of Shipwrecks
German Bomber
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
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
HV vs. HH
Multiband Color Composite
Alaska Coast
Reflectivity and
Penetration, Florida
Reflectivity, Southern California
IR + Radar
Radar Penetration of Sand, Sudan
Ground Penetrating Radar
Optical and Radar Imagery
TOPEX/Poseidon
The Sea Is Not Flat
Pacific Ocean Sea Surface
Changes
Sea Surface Radar Mapping
2004 Tsunami
Global Wind
Speed and Wave
Heights
Radar Image of Hawaii
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
Lidar
Mount St.
Helens
Neolithic Mound, Slovakia
Hopewell Mounds, Ohio
Hopewell Mounds Ground View
Caracol, Belize
Caracol, Belize
Caracol, Belize
Caracol, Belize, Point Cloud
Bainbridge Island, WA
Tacoma Fault and Glacial Troughs