Introduction toAdvanced and supporting

TechnologiesBy: Dr. Kamal M. Ahmed

Introduction• Why this lecture???• Definition: Remote Sensing is the science of

obtaining information about an area, object, or phenomenon through the analysis of data acquired by a device which is not in contact with the object, area, or phenomenon under investigation.

• Reading a text is a remote sensing operation.• Importance for engineers: mapping, planning,

interpretation, etc.• Energy, mainly from the sun, propagate through the

atmosphere, reflected or re-emitted from the objects, and recorded by “sensors”.

The Electromagnetic Spectrum• Visible wave lengths are very limited , 0.4 to 0.7 μm, Near

IR 0.7 to 1.3 μm, mid IR 1.3 to 3 μm. They both can be recorded on films.

• Thermal IR is mainly emitted from an object, needs thermal scanning.

• Microwaves are very long waves 1mm to 1m• Most common sensing systems operate in one or several of

the visible, IR, or microwave portions of the spectrum.• Energy emitted by the sun is within the visible portion,

while the energy emitted by the earth is within the thermal IR portion.

The Electromagnetic Spectrum

Spectral Reflectance• The ratio between the reflected energy and the

incident energy at a certain wave length.• A certain object will have different spectral

reflectance at different wave lengths• Different objects will have different spectral

reflectance at the same wave length• Examples: 1) Deciduous VS coniferous trees.

2) Vegetation VS soil and water. • Why do we see trees “green”.

Wavelength µm

Ref

lect

ance

%Dry soil gray brownVegetation greenWater clear

Infrared color photo

Normal Color photo

Notice the difference in color between natural vegetation and artificial turf

Normal Color photo

Color infrared photo

Normal B/W photo

0.4 to 0.7 µm

B/W Infrared photo 0.7 to 0.9 µm

Deciduous (needle) trees reflect more, brighter

Deciduous (needle) and coniferous trees (broad leaves) reflect the same

Thermal and Multispectral scanners• Thermal scanners will detect the emitted energy in

the thermal IR band.• Multispectral scanners will detect the reflected

energy in the visible, IR and microwave bands.• They include a number of detectors corresponding to

the number of bands (ranges of wavelengths) detected.

Earth Resources Satellites• US “LnadSat”:

– Ground coverage 185 km x 185 km. Equals to 1600 photos at 1: 20,000 with no overlap.

– Sensors: Multispectral scanner (MSS), Thematic Mapper (TM) . – best resolution: 30 m in black and white, LandSat 7 can reach 15

m• French “Spot”:

– Ground coverage is 60 x 60 km– Sensors: High Resolution Visible (HRV). Operates within a

limited band width: 0.51 to 0.89. – Resolution of 10 m in B/W, spot 5: 2.5 m

•Spot has a better spatial resolution and less spectral resolution than LandSat•Spot imaging system can be oriented to survey a certain area at a certain time and to produce stereo pairs.•Other available systems of higher resolution:

IKONOS, figure 27-23, 1 m resolution, and Spin-2 2m resolution. •Quick Bird: Resolution up to 60 cm is commercially available today.

Spot twin system

French Alps 3D model generated from Spot images

SPOT 10m resolutionB/W Image

LA, California

Digital Elevation Model (DEM) of the Grand Canyongenerated from Spot imagery

Cairo IKONOS 4m COLOR

Giza Pyramids 1m Ikonos

Cairo stadium 1m IKONOS

Compliments of Geobits

Matrouh Airport 60cm Quick Bird

Compliments of Geobits

Quick Bird 60cm image

1m Ikonos Image in Jamaica

Santiago 1m Ikonos Image

Washington D.C 5M IRS Image

2 m resolution satellite image of Giza-Egypt, courtesy of Spin-2

Daytime thermal imageQuantico, VA

NighttimethermalIMAGE

HEAT LOSS at 2:00am