Introduction to Remote SensingIntroduction to Remote SensingGenevieve Patenaude

genevieve.patenaude@ed.ac.uk

Courtesy of the Environment AgencyCourtesy of the Environment Agency

You are here!You are here!Edinburgh seen by Edinburgh seen by LiDARLiDAR

OverviewOverview

• Fundamentals• What is RS• How it works• What is recorded• What is meant by resolutions

• The systems• Optical, Lidar• Radar

• Example of systems and related costs• Where : Acquisition of images• What we need to be aware of when purchasing

Fundamentals

What is remote sensing?What is remote sensing?

The science (and art) of acquiring informationabout an object, without entering in contactwith it, by sensing and recording reflected oremitted energy and processing, analyzing,

and applying that information.

Passive RS Passive RS systemssystems

Active RSActive RSsystemssystems

Receiving stationsReceiving stations

InterpretationInterpretation

Final productFinal productApplicationApplication

• Energy source: Passive/Active• Atmosphere• Target• Recording devices• Transmission/reception/processing• Interpretation• Application

How it works?How it works?

What is recorded?What is recorded?

Courtesy of Louis E. Kleiner

Wavelengths

The resolutionsThe resolutions

Spectral resolution: Ability of sensor to separate EM into small intervals (bands)

Spatial resolution: The ground area represented by each pixel in an image

Multispectral: Hyperspectral:

Temporal resolution: How often is the target sampled(orbital characteristics, swath width, flight campaigns)

High resolution Low Resolution

Radiometric resolution: Ability to discriminate slightdifferences in energy

Courtesy of North Carolina UniversityCourtesy of North Carolina University

TheSystems

The systemsThe systems

Three main types of sensors used

• Optical (Visible/IR)• Radar (Microwave)• LiDAR (Mostly NIR)

Fundamentals of each

The systems: OpticalThe systems: OpticalOptical record energy in the visible/IR portion of the electromagnetic radiation

Energy recorded in bands: multi/hyperspectralSpectral signature: How reflects/absorbsradiation per wavelengths.Can be plotted as a spectral curve.

Unique spectral signature of vegetation

Specific bands used alone, or asratios to discriminate vegetations

A: blue bandB: green bandC: red bandD: near IR bandE: short-wave IR band

The spectral signature is also used to discriminate between vegetation types andconditions

Stress: damage to internal cell structure, reduction of chlorophylland of moisture content are factors which will affect the signature

The systems: OpticalThe systems: Optical

© Iain H. Woodhouse

The systems: RadarThe systems: RadarAdvantages over optical: active system, not affected by atmosphere,

penetrates the canopy (wavelength)

30 - 1000.3 - 1.0P15 - 304.8 - 8.0L

3.8 - 7.54.8 - 8.0C2.4 - 3.88.0 - 12.5X

Wavelength(cm)

Frequency(GHz)

RadarBand

Important limitations: forestry applications not fully operational/research stage

TIM

E (n

anos

ec)

0

50

100

PUSE INTENSITY

FIRST RETURN(top of canopy)

LAST RETURN(ground)

LASER PULSE

TIM

E (n

anos

ec)

0

50

100

PUSE INTENSITY

FIRST RETURN(top of canopy)

LAST RETURN(ground)

LASER PULSE

TIM

E (n

anos

ec)

0

50

100

PUSE INTENSITY

FIRST RETURN(top of canopy)

LAST RETURN(ground)

LASER PULSE

©©Hill Hill et al.et al. 2002 2002

The systems: The systems: LidarLidar•Light detection and ranging (Lidar)

•Active system (independent of sunlight)/ Functioning

•Not an imaging system: record discrete sample points

•Waveform and discrete recording LiDAR

•Unavailable from satellite

•Expensive

Example of systemsand related costs

What are the costs?What are the costs?

http://www.npagroup.co.uk/imagery/satimagery/pdf/price_list.pdfhttp://www.infoterra-global.com/

Multispectral (Medium)10-20 metres(£1800/ 60x60 km2 )

£0.5Spot1986 to –

http://www.ordnancesurvey.co.uk/oswebsite/

Variable (High)~ £25Aerialphotography

http://www.infoterra-global.comhttp://www.environment-agency.gov.uk/science/monitoring/131047/?version=1&lang=_e

(cost dependent onsampling density andservice providers)

~ £250Lidar

http://www.npagroup.co.uk/imagery/satimagery/ikonos.htm

Multispectral (High)1-4 metres(£1089 / 11x 11 km2)

£9Ikonos1999 to –

http://edc.usgs.gov/products/satellite/aster.html

Multispectral (Medium-High)15 to 90 meters(£50/~60x60 km2)

£0.01Aster2000 to –

http://edc.usgs.gov/products/satellite/tm.html

Multispectral (Medium)30 meters(£235/ ~170x180 km2)

£0.01Landsat 5&71982 to –

Sales contactSales contactType (spatial res.)Type (spatial res.)Cost/Cost/kmkm22

SensorsSensors

Free imagery (archive) at : http://glcf.umiacs.umd.edu/data/

New generation/Forthcoming sensorsNew generation/Forthcoming sensors

Applications to ForestryApplications to ForestryNational agencies/companiesNational agencies/companies• Clear cut mapping / regeneration assessment• Disturbances• Infrastructure mapping / operations support• Forest inventory / biomass estimation• Vegetation density• Species inventory

Environmental MonitoringEnvironmental Monitoring• Deforestation• Species inventory/ habitat mapping• Watershed protection• Coastal protection• Forest health and vigour

• Increasing number of sensors available (fromvideography, hand held digital cameras and highresolution satellite imagery)

• Transition from theory to information– Greater technological sophistication (Technological

advances)– Explosive growth in information extraction (Data

processing)– Improvement in understanding role of RS for forestry

(Information Synthesis)– The use of RS to generate specific information

requirements (Application context)

ConclusionConclusion