Geography 372Introduction to Remote Sensing

University of MarylandCompton Tucker & Megan Weiner

Remote Sensing CreedRemote Sensing Creed

I want to understand the worldI want to understand the world

I must use the electromagnetic spectrum I must use the electromagnetic spectrum (few other options)(few other options)

I will not be limited by a sensory system I will not be limited by a sensory system (the human eye) optimized for viewing (the human eye) optimized for viewing things in the light from a 6000 K star things in the light from a 6000 K star

93M miles away, whose electromagnetic 93M miles away, whose electromagnetic irradiance also has to pass through irradiance also has to pass through Earth’s NEarth’s N22-O-O22 planetary atmosphere planetary atmosphere

All alone in our neighborhood of spaceAll alone in our neighborhood of space

Apollo 12’s Classic Earth Rise from Moon

RemoteRemote Sensing Systems Sensing Systems

How do we discuss and catagorize remote sensing?

“the resolutions”SpatialSpatial Resolution -- what size we can resolve

SpectralSpectral Resolution -- what wavelengths do we use

RadiometricRadiometric Resolution -- degree of detail observed

TemporalTemporal Resolution -- how often do we observe

True & False Color Ikonos Satellite Data Beltsville Agricultural Research CenterBeltsville Agricultural Research Center

In visible light these trees look the sameIn visible light these trees look the same Near-infrared separates Near-infrared separates conifers (darker) from conifers (darker) from

deciduous treesdeciduous trees400 500 600 700nm

Spatial resolutionSpatial resolutionEach square in Each square in the image is one the image is one digital number digital number

for each spectral for each spectral band. The band. The

dimensions of the dimensions of the square square

determines determines spatial resolution. spatial resolution.

Better spatial resolution

Mars “Face” Viking 1976 Mars “Face” Viking 1976 resolution = ~200 mresolution = ~200 m

Mars Orbiter 2000 Mars Orbiter 2000 resolution = ~10 mresolution = ~10 m

Multistage Multistage Remote Remote SensingSensing

Ground-based remote sensingGround-based remote sensing

Air Air Photo:Photo:

color film, color film, airplane, airplane,

1-2 m 1-2 m detaildetail

TimothyTimothyLake, ORLake, OR

Landsat 30 mLandsat 30 mColumbia River Mt. St. Helens Mt. Adams

AVHRR 1 kmAVHRR 1 km

Columbia River

Olympic Pen.

Yellowstone N.P.

Mt. St. Helens

Satellite Remote Sensing of EarthSatellite Remote Sensing of Earth

SeaWiFS Land-Ocean Chlorophyll SeaWiFS Land-Ocean Chlorophyll September 1997 to present …September 1997 to present …

• Remote sensing uses the radiant energy that is Remote sensing uses the radiant energy that is reflected and emitted from Earth at various reflected and emitted from Earth at various “wavelengths” of the electromagnetic spectrum“wavelengths” of the electromagnetic spectrum

• Our eyes are only sensitive to the “visible light” Our eyes are only sensitive to the “visible light” portion of the EM spectrumportion of the EM spectrum

• Why do we use nonvisible wavelengths?Why do we use nonvisible wavelengths?

The Electromagnetic SpectrumThe Electromagnetic Spectrum

our star

Our Sun emits more light in the visible than any other part of the spectrum.

Amount of solar energy hitting Earth’s outer atmosphere is

~1370 watts/m2

Rayleigh Scattering:Rayleigh Scattering:why the sky is bluewhy the sky is blue

Remote Sensing Remote Sensing Systems:Systems:

the Human Eyethe Human Eye

• SpectralSpectral Resolution: 0.4-0.7 µm

• SpatialSpatial Resolution: ~ 1-3 cm @ 20 m

• RadiometricRadiometric Resolution: ~16-32 shades B/W or ~100 colors

Invertebrate remote sensingInvertebrate remote sensing

Insects have Insects have remote sensing remote sensing

capabilities capabilities quite different quite different

from from vertebrates and vertebrates and

the octopusthe octopus

Key Milestones in Remote SensingKey Milestones in Remote Sensingof the Environmentof the Environment

1826 – Joseph Niepce takes first photograph1858 – Gaspard Tournachon takes first aerial photograph from

a balloon1913 – First aerial photograph collected from an airplane1935 – Radar invented1942 – Kodak patents color infrared film1950s – First airborne thermal scanner1957 – First high resolution synthetic aperture radar1962 – Corona satellite series (camera systems) initiated by the

Intelligence community1962 – First airborne multispectral scanner1972 – ERTS-1 Launched – First Landsat satellite

Early photograph byEarly photograph by J. NiepceJ. Niepce circa1830 circa1830

Nadir in his Nadir in his balloonballoon

Nadir photograph of ParisNadir photograph of Paris

Balloon Photo Balloon Photo of Boston 1836of Boston 1836

Thaddeus Lowe’s Civil War BalloonsThaddeus Lowe’s Civil War Balloons U.S.Army of the Potomac 1861-1865U.S.Army of the Potomac 1861-1865

Massachusetts’ man, Professor and visionary, Lowe Observatory/Calif.

Platform: Balloon

Sensor: Telescope

Data System: Telegraph

Thaddeus Lowe, Thaddeus Lowe, circa 1861-1865 circa 1861-1865

remote sensing for remote sensing for military purposes. military purposes.

Then, as now, newest Then, as now, newest developments are developments are

always in the military always in the military spheresphere

Remote Remote sensing early sensing early

in the in the airplane eraairplane era

U-2 Spy Plane 1954-1960U-2 Spy Plane 1954-1960Flew at 70,000’ over USSR air defensesFlew at 70,000’ over USSR air defenses

SR-71 Blackbird super-sonic spy planeSR-71 Blackbird super-sonic spy plane

CIA’s Corona ProgramCIA’s Corona Program1960-1972 >100 missions

Followed after U-2s…

Platform: Spacecraft

Sensor: Camera

Data System: Film Drop

Started: August 1960

Coverage: 7.6 Bil mi2

Spatial Resolution: early missions @ 13 m, later missions @ 2 m

Spectral Resolution: visible and visible-near infrared (both film)

Radiometric Resolution: equivalent 24 to 26 (4 to 6 bits)

CIA’s Corona ProgramCIA’s Corona ProgramWashington Monument 1967

Ikonos 1 m panchromatic Ikonos 1 m panchromatic imageryimagery 20002000

MODIS Land Reflectance and MODIS Land Reflectance and Sea Surface TemperatureSea Surface Temperature