pictures are worth a thousand words…. introduction to remote sensing spatial, spectral, temporal...

Pictures are worth a thousand words…

Introduction to Remote Sensing

Spatial, spectral, temporal resolutions Image display alternatives Vegetation Indices Image classifications Image change detections Accuracy assessment Satellites & Air-Photos

Selected RS Systems

Landsat TM & Enhanced TM (Thematic Mapper) Ikonos & Quickbird MODIS (Moderate Resolution Imaging Spectrometer) Radarsat & ERS (European RS Satellite) SeaWiFS (Sea-Viewing Wide Field-of-View Sensor) GOES (Geostationary Operational Environ. Satellite) AVHRR (Advanced Very High Resolution Radiometer) SPOT (High Resolution Visible) Others

Digital Satellite Data

Digital satellite data is one type of remotely-sensed data aerial photography is another type of remotely-sensed geographic information

Important advantage of remote sensing data: synoptic perspective: comprehensive view of large areas of the Earth’s

surface, vantage point of observation, digital format, multi-spectral, multi-temporal, multi-spatial.

Remote sensing: the acquisition of data about an object or area by a sensor that is physically far from the object or area.

Satellite Data - Benefits & Problems

Benefits: it is already digital (unlike standard aerial photos)

-- readily lends itself to manipulation and analysis to extract useful information

synoptic perspective repeat coverage of areas minimal scale and geometric distortion problems relative to

aerial photos Problems:

generally low spatial resolution compared to aerial photos large data storage volumes distortions in data values due variations in atmospheric

conditions, clouds, terrain, solar angle, etc... -- require preprocessing to correct!

Electromagnetic Spectrum (EMS)

0.4 0.5 0.6 0.7

Visible Portion

Cosmic Gamma X-rays UV Infrared Microwave Radio/TVRays Rays Near/Medium/Thermal

Increasing Wavelength

Increasing Frequency and Energy

At a given Temperature

, T

10-6 10-4 10-2 1 102 104 106 108

Wavelength in Micrometers (= 103 nanometers)

Incoming EMR

Reflected EMR

Emitted EMR

Passive (Optical) Sensor Technology

Electromagnetic Radiation Spectrum

Remote sensing satellites record data on electromagnetic radiation (EMR) satellites have detectors that record specific wavelengths

in the EM spectrum

EM radiation interacts with physical matter some wavelengths are absorbed & others reflected determine/estimate matter type by analyzing spectral

“signatures” in satellite data

“The Four RS Resolutions”

Satellite data characterized by four resolutions: spatial resolution: area on ground represented by each

pixel (cell) in the satellite data. temporal resolution: how frequently a satellite platform

obtains imagery of a particular area , orbital characteristics. spectral resolution: specific EM spectrum wavelength

intervals captured/recorded by a particular satellite sensor. radiometric resolution: number of possible data values

recorded/reportable by each satellite sensor, precision with which the EM spectral values are reported.

Aerial Photographs

Scale = Focal Length/Flying Height Principal Point & Conjugate PP Radial Displacement Parallax Forward-Lap & Side-Lap Stereoscopic Analysis & Stereoscopes See photos for examples

Satellite Data - Pixel Brightness Values

“Brightness Value” (BV) corresponding to intensity of EM radiation in specified spectral range detected for that pixel

lower BV = lower level of EM radiation detected higher BV = higher level of EM radiation detected

Displaying/viewing satellite data:

high BV

medium BV

low BV

For displaying/viewing satellite images: high BVs assigned

bright/light color value low BVs assigned

dark/dim color value

Satellite Data - Pixel Brightness Values & Display

Landsat TM Multi-Spectral Display :

+ =+

Band 4 - near infrared Band 3 - red visible Band 2 - green visible on-screen display:

+ =+

Band 2 - green visibleBand 4 - near infraredBand 7 - middle infrared on-screen display:

RED GUN GREEN GUN BLUE GUN

Infrared band (4)

Red color gun Green color gun

Red band (3)

Blue color gun

Green band (2)

RGB Compositing Process

Panchromatic Display

Panchromatic display of a single band

Visible red (red gun), green (green gun), blue (blue gun) – “true”color

Multispectral Composite Display

Near infrared (red gun), red (green gun), green (blue gun): “false color”

Multispectral Composite Display

Middle infrared (red gun), near infrared (green gun), green (blue gun): “false color”

Multispectral Composite Display

1-2 m 30 m 79 m 1.1 km QuickBird, Landsat TM, Landsat MSS AVHRR IKONOS ETM

Different Spatial Resolutions

Daytona 500 RacetrackFebruary 1995, NAPP (USGS

EDC)

Lake Lloyd

grandstands

racetrack

Mt. St. Helens, May 1980Aircraft photo

The North Pole, June 1992 AVHRR

The Earth at Night, DMSP mosaic

Kuwait Oil Fires, April 1991Space Shuttle

Smoke Plumes from Oil Fires

Middle East Oil Fires, November 4, 2002

MODIS

Thermal (Far Infrared) People

SeaWiFS of Europe & UK:

particulate pollution in

southern UK and dust cloud

in southern Spain

GOES Image of Hurricane Bonnie August 25, 1998

SeaWiFS of Greenland

July 15, 2000

Washington, DC Bands 4, 3, 2 (infrared, red, green)

Landsat 7 Enhanced Thematic Mapper (ETM+)

GOES Image of Water Vapor: Thermal Infrared Sensing

SeaWiFS of Sea Surface Temperatures

IKONOS Multi-Spectral Imagery

Digital Image Data

MSS 1973

TM 1999

IKONOS 1999

Ikonos Images & Survey Sketch