radar mapping. electromagnetic em radiation electric field & magnetic field –perpendicular to...

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