Geography 1010

Remote Sensing

Outline

• Last Lecture– Electromagnetic

energy.

– Spectral Signatures.

• Today’s Lecture– Spectral

Signatures.

– Satellite Remote Sensing.

Spectral signatures with TM bands

Band Selection and Colour Composite

Landsat MSS

• Launched in 1972 (just to try it out).

• Converted Geostationary bus.

• 1-3 are essentially the same system.

Landsat MSS

• 185 km swath width.• Parallelogram shape to

images.• Repeat coverage every 18

days (at equator).• Always crosses the

equator at the same solar time.

• Across-track scanner.

Orbital Parameters

• Sun Synchronous• 900 km altitude• 9º from North

• Orbital period– 103 minutes (14

per day)– 6.46 km/sec

Satellite Orbit

Landsat TM

• Sun synchronous orbit.• 705 vs. 900 km (improve

resolution and for potential recovery).

• Crosses equator at 9:45 am.

• 99 minute orbit.• 14.5 orbits per day.• 16 day repeat cycle.

Landsat TM

• 30m ground resolution.– Thermal is 120m.

• Bi-directional scanner.• 7 bands (6 visible / IR 1

thermal).• A/D converter produces

8-bit data (256 shades of grey).

Landsat ETM+ band 1 (0.45-0.52 µm, blue-green)

Landsat ETM+ band 2 (0.52-0.60 µm, green)

Landsat ETM+ band 3 (0.63-0.69 µm, red)

Landsat ETM+ band 4 (0.76-0.90 µm, near infrared)

Landsat ETM+ band 5 (1.55-1.75 µm, mid-infrared)

Landsat ETM+ band 6 (10.40-12.50 µm, thermal infrared)

Landsat ETM+ band 7 (2.08-2.35 µm mid-infrared)

Chernobyl.Chernobyl.

SPOT

• Commercial orientation not experimental.

• Began in 1986.• 20 metre multi spectral (XS).

– IR, red, green.

• 10 metre panchromatic (HRV).

• Receiving station on campus.

SPOT

• Repeat coverage every 26 days.

• Off nadir viewing (reduces repeat time).

•60 km swath for nadir•80 km for oblique (max 27°)•8-bit data•4.13° field of view

Spot

• Off nadir viewing Off nadir viewing creates image creates image parallax.parallax.

• Allows for the Allows for the creation of digital creation of digital elevation models.elevation models.

RADAR Principles

• Acronym for RAdio Detection And Ranging (although we rarely use radio frequencies (1 - 10 m)

• Active imaging system• Transmits short pulses or bursts of microwave radiation

and receives the reflection from the target. (Detection)• Can tell where the target is by timing the pulse (Ranging)

RADAR Principles

• Reflections from the target are called echo or backscatter.

• Active system...Day - Night imaging

• Sends out single wavelengths of EMR

• Records the strength of the return– Good reflectors are bright– Poor reflectors are dark

How It Works

• Mirror sweeps laser beam across the ground.

• Range to target is determined by measuring time interval between transmission and return of reflected laser pulse.

• Aircraft position is determined using GPS phase differencing techniques.

• Data streams recorded and synchronized for post processing.

GPS ground reference station

Aircraft GPS

GPS satellites

Flight direction

ALTM laser and IMU