Satellite/Aircraft Imaging Systems Imaging Sensors Standard scanner designs Image data formats

Transcription

1 CEE 6150: Digital Image Processing 1 Satellite/Aircraft Imaging Systems Imaging Sensors Standard scanner designs Image data formats

2 CEE 6150: Digital Image Processing 2

3 CEE 6150: Digital Image Processing 3

4 CEE 6150: Digital Image Processing 4 Typical whiskbroom scanner geometry Scanning design to improve dwell time: whiskbroom scanners Banding from Whiskbroom Scanner Differences in calibration of individual detectors Differences in calibration associated with scan direction

5 CEE 6150: Digital Image Processing 5 Spectral Band Selection: Landsat 5 (TM) and Landsat 7 (ETM+) TM Focal Plane Array

6 CEE 6150: Digital Image Processing 6 PUSHBROOM SCANNERS: Scanner geometry: SPOT Spatial Resolution (SPOT) (Since 1986) Mode Spectral Band Res. Multispectral (XS) SPOT 1,2,3,4,5 1 (Green) µm 20 m 2 (Red) µm 20 m 3 (Near IR) µm 20 m SPOT 4,5 4 (Mid IR) µm 20 m Panchromatic (P) SPOT 1,2, µm 10 m SPOT µm 10 m SPOT µm 2.5 m* Swath nadir: 60 km * The panchromatic band uses two 5 m sample arrays offset by 2.5 m in both the cross-track and along-track directions. This results in a quasi-2.5 m sample spacing, but with a resolution cell size of 5 m.

7 CEE 6150: Digital Image Processing 7 IKONOS (Space Imaging) Multispectral spatial dynamic Band Spectral Range (FWHM) Res. range nm (Blue) 4 m 11 bits nm (Green) 4 m nm (Red) 4 m nm (NIR) 4 m Panchromatic spatial dynamic Spectral Range (FWHM) Res. range nm (Blue) 1 m 11 bits swath nadir: 10 km Spectral Band Selection: QuickBird Multispectral spatial dynamic Band Spectral Range (FWHM) Res. range nm (Blue) 2.44 m 11 bits nm (Green) 2.44 m 11 bits nm (Red) 2.44 m 11 bits nm (NIR) 2.44 m 11 bits Panchromatic spatial dynamic Spectral Range (FWHM) Res. range nm (Blue) 0.61 m 11 bits swath nadir: 16.5 km Spectral Band Selection: WorldView-2 Multispectral nadir dynamic Band Spectral Range (FWHM) Res. range nm (Coastal) 1.84 m 11 bits nm (Blue) 1.84 m 11 bits nm (Green) 1.84 m 11 bits nm (Yellow) 1.84 m 11 bits nm (Red) 1.84 m 11 bits nm (Red Edge) 1.84 m 11 bits nm (NIR 1) 1.84 m 11 bits nm (NIR 2) 1.84 m 11 bits off-nadir Panchromatic nm (Panchromatic) 0.46 m 11 bits swath nadir: 16.4 km off-nadir Operational Land Imager (OLI; Landsat 8) Spectral bands: Focal plane array: balticbloom_oli_ _lrg.jpg Web Resources Satellite Imaging Corporation: High resolution commercial systems; system descriptions and access to imagery (for purchase). U.S. Government image data: Access to imagery (free, mostly); includes data descriptions

8 CEE 6150: Digital Image Processing 8 System Specs: AVIRIS (Visible-IR Imaging Spectrometer (AVIRIS) Data Rate: 17 Mbps through 1994, 20.4 Mbps from Bit depth: 10 bit through 1994, 12 bit from Detectors: Silicon (Si) for the visible range, indium-antimonide (InSb) for the NIR Scanning: "Whisk broom", 12 Hz scanning rate Spectral: 10 nm bandwidth, µm (224 bands) 20 km: 30 m GIFOV Color Pixel misregistration (design dependent) Color pixels along the edge of the road are due to nearestneighbor resampling of different spectral bands when the color registration is imperfect. 2-D CCD arrays folding mirror (static) diffraction grating 2-D array Scanner geometry: Hyperspectral flight path IFOV θ H H sec θ ω

9 CEE 6150: Digital Image Processing 9 Color Representation in Digital Cameras Bayer Pattern Digital Cameras have only one 2-D array A color filter array (CFA) is placed between the lens and the sensors. A CFA typically has one color filter element for each sensor. The Bayer pattern uses the three additive primary colors, red, green and blue (RGB), for the filter elements arranged in a 2x2 pattern.. Fuji X-trans color array (new) 1) lens, 2) low pass filters, 3) array Higher degree of randomness with an array of 6 x 6 pixel units. Without using an optical low-pass filter, moire and false colors are minimized while retaining high resolution. Inspired by the natural random arrangement of the fine grains of silver halide in film. Fovean camerathe layers of silicon take advantage of the fact that silicon absorbs different colors of light at different depths, so one layer records red, another layer records green and the other layer records blue.

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11 CEE 6150: Digital Image Processing 11 Orbital Mechanics The orbital speed of a body, in our case, a satellite, is the speed at which it orbits around the earth. Here, for simplicity, we consider only circular orbits and Newton's laws (nothing about energy or momentum). We further assume that only two objects (the earth and the satellite) need to be considered and that the mass of the satellite is negligible relative to the mass of the earth. In this case, the centripetal force, Fc, acting to drive the satellite away from the earth, and the gravitational force, Fg, attracting the satellite toward the earth, must balance exactly. Thus, if ms is the mass of the satellite, me, is the mass of the earth, G is the universal gravitational constant, and r is the distance from the center of the earth to the satellite, then: F c 2 s Gmsme ; Fg 2 = m v r = Gm v = e r r where r = re + h (the radius of the earth + the altitude of the satellite). An object moving faster than circular velocity will enter an elliptical orbit with a velocity at any point determined by Kepler's laws of planetary motion. If the object moves faster still, it will travel at escape velocity along a parabolic orbit or beyond escape velocity in a hyperbolic orbit. Orbital Period The orbital period T = 2π 3 r Gm e of a small body orbiting a central body in a circular or elliptical orbit is: The radium of the earth, re=6.378x10 6 m The standard gravitational parameter, μ = Gme=3.986x10 14 m 3 s -2 Orbital families LEO: low earth orbit, typical altitude < 2000 km o space shuttle o space station o Hubble Space Telescope o iridium o remote sensing: EROS, Landsat o communications: , text messaging, paging MEO: medium earth orbit, typical altitude 10,000 to 20,000 km o GPS: Global Positioning System GEO: geosynchronous earth orbit, seven earth radii, one-ninth of the distance to the moon, altitude = 36,000 km o GOES - Geosynchronous (Geostationary) Operational Environmental Satellites o communication: signal relays for terrestrial broadcast and cable systems direct broadcast satellite TV and radio o TDRS: Tracking and Data Relay Satellite