Introduction of Satellite Remote Sensing

Transcription

1 Introduction of Satellite Remote Sensing

2 Spatial Resolution (Pixel size) Spectral Resolution (Bands) Resolutions of Remote Sensing 1. Spatial (what area and how detailed) 2. Spectral (what colors bands) 3. Temporal (time of day/season/year) 4. Radiometric (color depth)

3 The ability to resolve, or separate, small details is one way of describing what we call spatial resolution. Spatial resolution of images acquired by satellite sensor systems is usually expressed in meters. For example, we often speak of Landsat as having 30-meter" spatial resolution, which means that two objects, thirty meters long or wide, sitting side by side, can be separated (resolved) on a Landsat image. Other sensors have lower or higher spatial resolutions. Landsat represents the world's longest continuously acquired collection of space-based land remote sensing data. It is considered the unique national assets. The first Landsat satellite was launched in 1972; the most recent, Landsat 7, was launched on April 15, The instruments on the Landsat satellites have acquired millions of images. The images, archived in the United States and at Landsat receiving stations around the world, are a unique resource for global change research and applications in agriculture, geology, forestry, regional planning, education and national security.

4 Landsat Missions Landsat 1 (07/12/ /06/1978) - RBV, MSS (80m) Landsat 2 (01/22/ /27/1983) - RBV, MSS (80m) Landsat 3 (03/05/ /07/1983) - RBV, MSS (80m) Landsat 4 (07/16/ ) - MSS, TM (30m, 120m TIR) Landsat 5 (03/01/ ) - MSS, TM (30m, 120m TIR) Landsat 6 (10/05/1993): ETM Landsat 7 (04/23/ ) - ETM+ (30m, 60m TIR, 15m Pan) Landsat Data Continuity Mission (LDCM) ?????? MSS: Multispectral Scanner TM: Thematic Mapper ETM+: Enhanced Thematic Mapper Plus Pan: Panchromatic TIR: Thermal Infrared RBV: Return Beam Vidicon Camera August 17, 2007, The Office of Science and Technology Policy (OSTP) released the National Land Imaging Program (NLIP) strategy. This program is designed to meet U.S. civilian moderate resolution land imaging needs to monitor the changes in land surface, Polar Regions, and coastal zones due to the changes in population growth, development and climate changes. It establishes a program office in the Department of the Interior, reporting at the Secretary and Assistant Secretary level, to provide focused leadership and management for the nation s land imaging efforts. NLIP will focus on maintaining a core, operational government commitment and capability to collect moderate-resolution land imagery through the procurement and launch of a series of U.S. owned satellites thereby ensuring the continuity of U.S. collected and managed Landsatlike data, well into future decades.

5 Landsat Landsat Multispectral Multispectral Scanner Scanner (MSS) (MSS) and and Landsat Landsat Thematic Thematic Mapper Mapper (TM) (TM) Sensor Sensor System System Characteristics Characteristics

6 Rhode Island: Path 12/Row 31

7 Landsat Ground Stations Rhode Island: Path 12/Row 31

8 Landsat Images of the World Launched: September 24, 1999 Ground resolution: 1-meter panchromatic ( µm), 4-meter multispectral (same as Landsat TM bands 1-4) 1. Band 1: µm (Blue) 2. Band 2: µm (Green) 3. Band 3: µm (Red) 4. Band 4: µm (Near IR)

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10 October 19, 2001 DigitalGlobe launched the QuickBird-2 satellite Spatial Resolutions: Panchromatic data: 0.6-meter Multispectral Data: 2.5-meter 1. Blue: mm 2. Green: mm 3. Red: mm 4. Near-IR: mm September 3, 2003 QuickBird Satellite Panchromatic Images (0.6-m Spatial Resolution)

11 QuickBird satellite image of the Jamaica Bay acquired on September 10, This is a true color display. DigitalGlobe WorldView I First Images (Houston) WorldView I, launched September 2007, collects 0.5-meter resolution imagery with an average revisit time of 1.7 days. WorldView II, is anticipated to launch in late 2008, pending finalization of customer contracts meter panchromatic resolution and 1.8- meter multispectral resolution, an average revisit time of 1 day.

12 DigitalGlobe WorldView I First Images (Yokohama) WorldView I, launched September 2007, collects 0.5-meter resolution imagery with an average revisit time of 1.7 days. WorldView II, is anticipated to launch in late 2008, pending finalization of customer contracts meter panchromatic resolution and 1.8- meter multispectral resolution, an average revisit time of 1 day. GeoEye-1, a Google sponsored satellite, was successfully launched September 6, October 13, 2008, GeoEye released its first image.

13 GeoEye Satellite Image taken at 11:19AM shows Washington D.C.'s National Mall and the U.S. Capitol on Jan. 20, 2009 during the Presidential inauguration. GeoEye's next satellite, GeoEye-2, is in a phased development process for an advanced, third-generation satellite capable of discerning objects on the Earth s surface as small as 0.25-meter (9.75 inch) in size. The company expects to contract with a satellite builder in 2008 and launch the satellite approximately three years after work begins under that contract.

14 Resolutions of Remote Sensing 1. Spatial (what area and how detailed) 2. Spectral (what colors bands) 3. Temporal (time of day/season/year) 4. Radiometric (color depth) Spectral Response Curve

15 Spectral Resolution Number of spectral bands (red, green, blue, NIR, Mid-IR, thermal, etc.) Width of each band Certain spectral bands (or combinations) are good for identifying specific ground features Panchromatic 1 band (B&W) Color 3 bands (RGB) Multispectral 4+ bands (e.g. RGBNIR) Hyperspectral hundreds of bands Spectral Cover of Landsat Sensors Band 1: µm (blue). Provide increased penetration of water bodies, as well as supporting analysis of land use, soil, and vegetation characteristics. Band 2: µm (green). This band spans the region between the blue and red chlorophyll absorption bands and therefore corresponds to the green reflectance of healthy vegetation. Band 3: µm (red). This is the red chlorophyll absorption band of healthy green vegetation and represents one of the most important bands for vegetation discrimination.

16 Spectral Cover of Landsat Sensors Band 4: µm (reflective infrared). This band is responsive to the amount of vegetation biomass present in the scene. It is useful for crop identification and emphasizes soil-crop and land-water contrasts. Band 5: µm (mid-infrared) This band is sensitive to the amount of moisture in plants and therefore useful in crop draught and in plant vigor studies. Band 6: µm (thermal infrared) This band measures the amount of infrared radiant flux emitted from surface. Band 7: µm (mid-infrared) This is an important band for the discrimination of geologic rock formation. It is effective in identifying zones of hydrothermal alteration in rocks.

17 Comparison of Landsat Sensors Spectral Resolution (µm) Spatial Resolution (meter) Temporal Resolution (revisit in days) Spatial coverage (km) Thematic Mapper (TM) Landsat 4 and (B) (G) (R) (NIR) (MIR) (MIR) (TIR) 30 x x 120 (TIR) Enhanced Thematic Mapper Plus (ETM+) Landsat (Pan) 15 x 15 (Pan) 30 x x 60 (TIR) Multispectral Scanner (MSS) Landsat (green) (red) (NIR) (NIR) 79 x (Landsat 1,2,3) 185 x x x 185 Altitude (km) (Landsat 1,2,3) Landsat-7 ETM+ Data of Providence Landsat-7 Panchromatic Data (15 m) Landsat-7 ETM+ Data (30 m), Bands 3, 2, 1 in RGB Landsat-7 ETM+ Data (30 m), Bands 4, 3, 2 in RGB Landsat-7 ETM+ Data (30 m), Bands 4, 5, 3 in RGB

18 Comparison of Enhanced Spatial Resolution QuickBird Multispectral Image and True Color Orthophoto QuickBird-2 Satellite Spatial Resolutions: 0.61 meter panchromatic; 2.5 meters multispectral

19 TERRA (EOS AM) - Launched December 18, 1999 The following instruments fly on TERRA: ASTER: Advanced Spaceborne Thermal Emission and Reflection Radiometer (15m - 3 bands in VNIR; 30m - 6 bands in SWIR; 90m - 5 bands in TIR) MODIS: Moderate Resolution Spectroradiometer ( µm) (250m - 2 bands, 500m - 5 bands, 1000m - 29 bands) CERES: Clouds and the Earth's Radiant Energy System MISR: Multi-angle Imaging Spectroradiometer MOPITT: Measurements of Pollution in the Troposphere. EO-1: successfully launched on November 21, 2000 ALI - Advanced Land Imager consists of a 15 Wide Field Telescope (WFT) and partially populated focal plane occupying 1/5th of the field-of-view, giving a ground swath width of 37 km. Hyperion Hyper-spectral sensors a grating imaging spectrometer having a 30 meter ground sample distance over a 7.5 kilometer swath and providing 10nm (sampling interval) contiguous bands of the solar reflected spectrum from nm. LEISA/LAC - Linear Etalon Imaging Spectrometer Array Atmospheric Corrector (LAC) an imaging spectrometer covering the spectral range from 900 to 1600 nm which is well suited to monitor the atmospheric water absorption lines for correction of atmospheric effects in multispectral imagers such as ETM+ on Landsat. A comparison with Landsat 7 is included.

20 Hyperspectral data Such as Hyperion sensor on board the EO-1 Satellite and Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) Spectral profile in a single pixel location from 0.4 to 2.5 µm at 10 nm interval for a continuous coverage over 220 bands AVIRIS EO-1 launched November 21, 2000 Different surface types such as water, bare ground or vegetation reflects radiation differently in various channels. The radiation reflected as a function of the wavelength is called the spectral signature of the surface

21 Concept of Hyperspectaral Remote Sensing Resolutions of Remote Sensing 1. Spatial (what area and how detailed) 2. Spectral (what colors bands) 3. Temporal (time of day/season/year) 4. Radiometric (color depth)

22 Temporal Considerations Time of Image Acquisition Seasonal differences Phenological differences Relationship to field sampling Landscape dynamics Land use and land cover changes Forest Cover 1987 Mt. Kilimanjaro (5,895m) Mt. Meru (4,566m)

23 Forest Cover 2000 Mt. Kilimanjaro (5,895m) Mt. Meru (4,566m) Landsat June 21, 2000 Pre-fire Sanford fire site Central Utah

24 Landsat June 14, 2003 Post-fire Sanford fire site Central Utah 1973 Mount St. Helens in southwestern Washington (before and after the volcanic eruption in 1980) 1988

25 Resolutions of Remote Sensing 1. Spatial (what area and how detailed) 2. Spectral (what colors bands) 3. Temporal (time of day/season/year) 4. Radiometric (color depth) Radiometric Resolution Every time an image is acquired by a sensor, its sensitivity to the magnitude of the electromagnetic energy determines the radiometric resolution. The finer the radiometric resolution of a sensor, the more sensitive it is to detecting small differences in reflected or emitted energy.

26 Imagery data are represented by positive digital numbers which vary from 0 to a selected power of 2. This range corresponds to the number of bits used for coding numbers in binary format. Each bit records an exponent of power 2. The maximum number of brightness levels available depends on the number of bits used in representing the energy recorded. Thus, if a sensor used 8 bits to record the data, there would be 2 8 =256 digital values available, ranging from 0 to bits 11 bits Number of bits Maximum Values Data volume will increase as the radiometric resolution increases? Shuttle Radar Topography Mission (SRTM), February 11-22, 2000, obtained the high-resolution digital topographic database of the Earth Mt. Kilimanjaro (5,895 m) Geographic Information for Sustainable Development (GISD) Digital Elevation Model (DEM) in GIS Tanzania/ Kenya Coastal Zone

27 Lake Eyasi Ngorongoro Crater SeaWiFS Level-3 Standard Mapped Image October 2001 SeaWiFS Level-3 Standard Mapped Image October 1997 Credit line for all images: Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center and ORBIMAGE

28 Examples of SeaWiFS Images Multispectral Multitemporal Multisensor Multiresolution Remote Sensing Data Spatial, Temporal, and Spectral Resolutions