NON-PHOTOGRAPHIC SYSTEMS: Multispectral Scanners Medium and coarse resolution sensor comparisons: Landsat, SPOT, AVHRR and MODIS

Transcription

1 NON-PHOTOGRAPHIC SYSTEMS: Multispectral Scanners Medium and coarse resolution sensor comparisons: Landsat, SPOT, AVHRR and MODIS

2 CLASSIFICATION OF NONPHOTOGRAPHIC REMOTE SENSORS PASSIVE ACTIVE DIGITAL CAMERA VIDEO CAMERA MULTI- SPECTRAL SCANNERS MICROWAVE SAR LASER THERMAL (e.g. TIMS) VISIBLE & NIR HYPERSPECTRAL (e.g. AVIRIS) ACROSS TRACK (sweep) e.g. Landsat, AVHRR ALONG TRACK (push) e.g. SPOT

3 ACROSS-TRACK / MULTISPECTRAL SCANNING OPERATION scan angle (IFOV) An oscillating mirror scans across the terrain at right angles to the flight path mirrors direct the radiation from the IFOV to spectrum-separating devices which divide the signal into discrete bands or channels the signal from each band is focused on detector elements that transform the radiation into an electrical signal, which is recorded and stored digitally scan lines pixel

4 ALONG-TRACK SCANNING OPERATION linear array of CCDs scan perpendicular to the flight line (no mirrors) each CCD senses energy from a single ground resolution cell (pixel) each spectral band (channel) requires its own CCD array each scan line is viewed by all channel arrays simultaneously

5 NON-PHOTOGRAPHIC SYSTEMS Advantages of along-track scanners linear arrays afford longer residence time for which to measure energy from each ground resolution cell, resulting in a stronger signal fixed relationship of CCDs along each scan line results in improved geometric integrity CCDs small in size and require less power for operation w/o moving parts (e.g. oscillating mirrors), a linear array system has a higher reliability and longer life expectancy

6 LANDSAT PROGRAM (USA) The Landsat Concept (emerged in late 1960s) Launch a dedicated, unmanned land-observing satellite to collect, archive and distribute remotely sensed data to users in agriculture, forestry, environmental science, geology, land cover/use, water resources, and marine science. History Landsat-1 launched in July, 1972 Landsats 1-3 carried RBV and MSS sensor Landsat-4, launched 1982, carried new Thematic Mapper (TM) sensor, Landsat 5 also carries TM. Landsat 5 recently decommissioned (November 2012) Landsat 6 launch failed Landsat-7, with Enhanced TM sensor, launched April 1999, but developed a line scan anomaly problem that compromised the data and made it unusable for most users Landsat 8 Operational Land Imager (OLI) launched February 2013

7 TM Bands: Wavelength (mm) TM scene: bands 4,5,3 color composite (Sioux Falls, SD) 8 bit data (0-255 DNs) data strips framed into a 185x185 km scene 30m ground resolution per pixel with non-thermal detectors (120m for thermal band 6) Landsat 8 OLI bands are similar to Landsat TM except two visible blue bands so band 1 TM is band 2 OLI, TM 3 is OLI 4, etc.

8 LANDSAT TM: sensor applications OLI band TM Band Wavelength Range (mm) Spectral Region Applications Blue water penetration, coastal mapping, soil/veg. discrimination, cultural feature ID Green Chlorophyll reflection band (peak green reflectance of veg.), veg. ID and vigor, cultural feature ID Red Chlorophyll absorption band (Vegetation discrimination), cultural feature ID Near IR Veg. types, plant stress, biomass content, soil mositure discrimination, water delineation Mid-IR Soil and veg. moisture content, clouds vs. snow Thermal IR Vegetation stress, soil mositure discrimination, thermal mapping Mid-IR Veg. moisture content, rock and mineral discrimination

9 Landsat 8 Operational Land Imager (OLI) Landsat Data Continuity Mission (LDCM) Bands Wavelength (micrometers) Band 1 - Coastal aerosol Band 2 - Blue Band 3 - Green Band 4 - Red Band 5 - Near Infrared (NIR) Band 6 - SWIR Band 7 - SWIR Band 8 - Panchromatic Band 9 - Cirrus Resolution (meters) Band 10 - Thermal Infrared (TIRS) Band 11 - Thermal Infrared (TIRS) Worldwide Reference System-2 (WRS-2) path/row system Sun-synchronous orbit at an altitude of 705 km (438 mi) 233 orbit cycle; covers the entire globe every 16 days (except for the highest polar latitudes) Inclined 98.2 (slightly retrograde) Circles the Earth every 98.9 minutes Equatorial crossing time: 10:00 a.m. +/- 15 minutes

10 LANDSAT TM data acquisition for Maine Worldwide Reference System (WRS)- 8 scenes Imagery archived and catalogued by USGS EROS Data Center (Sioux Falls) Glovis Search archive on web for available imagery Search parameters: WRS Path / Row date maximum cloud cover browse images

11 SPOT Sensor System (French) Systeme Pour l Observation de la Terre (SPOT) French Space Agency, along-track (pushbroom) scanner SPOT-1, SPOT-2 and -3 (launched 1986, 90 and 93, respectively): 3 spectral bands (20m ground resolution) + Panchromatic band (10m) SPOT-4 (1998), adds 20m Middle Infrared (MI) or Short Wave Infrared (SWIR) band SPOT-5 (2002), 10 m multispectral (3 bands), 20m MI or short wave, 5m panchromatic (2 sensors capable of 2.5 m panchromatic) Two identical High Resolution Visible (HRV) imaging systems (using CCD detector arrays): 1 Panchromatic, 1 multispectral pointable optics enable nadir and off-nadir scanning for greater repeat coverage and stereo viewing used in forestry, agriculture, ecological, land cover/use, and topographic mapping applications

12 SPOT PROGRAM orbital and sensor characteristics sun-synchronous orbit altitude: 822 km orbital period: 101 minutes (14+ orbits/day) repeat coverage (nadir): 26 days however off-nadir:approx. 5 days swath: 60km at nadir, 80km on west and east off-nadir High Resolution Visual (HRV) sensor

13 NOAA SATELLITES (USA) Advanced Very High Resolution Radiometer (AVHRR) sensor National Atmospheric and Oceanic Administration meteorological satellites (7 in series) now with 5 spectral bands: 1 visible, 1 near-ir, 3 thermal-ir applications: weather and climate; water surface temperature measurement; snow cover mapping; flood monitoring; global vegetation mapping and changes; regional soil moisture, fire, storm, and volcanic monitoring; mapping regional drainage and physiographic features

14 AVHRR orbital characteristics Altitude: 833km 2400 km swath width 1.1 km ground resolution at nadir twice daily coverage Daylight and nighttime orbits

15 SENSOR COMPARISONS spectral resolution (#bands and location) Thermal 4 Reflected Mid_infrared

16 MODIS (USA) Orbit: Swath Dimension Orbit, swath width and sensor resolution Multi-resolution (250, 500, 1000m) and hyperspectral at 1000m resolution 705 km, 10:30 a.m. descending node (Terra) or 1:30 p.m. ascending node (Aqua), sun synchronous, near-polar, circular 2330 km (cross track) by 10 km (along track at nadir) Launch Dates Spatial Resolution TERRA_MODIS December 1999 AQUA_ MODIS May m (bands 1-2) 500 m (bands 3-7) 1000 m (bands 8-36)

17 MODIS (250m,500m) and Landsat TM and Reflected Bands Comparison Band/Sensor MODIS Landsat Red µm µm NIR µm µm Blue µm µm Green µm µm Middle-IR µm Middle-IR µm µm Middle-IR µm µm Resolution 250m, 500m 30 m Swath width 2330 km 185 km Temporal Daily 16 days Price Free $600/scene Landsat 8 OLI Free as of 2009

18 SENSOR COMPARISONS area covered by one scene

19 SENSOR COMPARISONS and Data Costs Cost Update (4/2009) Old! Costs MSS free if available TM/ETM+/OLI(30m) = Free (ETM+ includes 15m Pan) SPOT-4(MS or Pan)= $1900? SPOT-5(10m or 5m)= $3375? AVHRR/MODIS are Free- Internet download

20 Ecosystem Sensor System Spatial Extent Grain Size Plant ID Level Biome, continent Regional, country State, ecoregion, watersheds Local landscape, forest stands Forest plot AVHRR, MODIS 1000m MODIS 250m, Landsat TM and OLI Landsat, TM and OLI, SPOT, others, SAR Spot, IKONOS, LIDAR, Digital Cameras, Aircraft Hyperspectral Highest resolution sensors, ground Hundreds of thousands sq. km. Thousands of sq. km. Hundreds of sq. km. Tens to low hundreds of sq. km. < ten sq. km. to one-ten ha or less 1 km 500m General land cover (Level 1) m General land cover (level 1-2) m Forest type (level 2-3) 10 1m Forest type/species group and detailed land cover (Level 3-4) 1m 1 ft Tree or canopy measurement, some single species ID

21 SENSOR COMPARISONS Landsat MSS archival, historical (no longer collected), oldest earth resource satellite at medium spatial resolution (1972) Landsat TM, ETM+& Landsat 8 OLI improved multispectral resolution (7 bands (more for OLI). Older TM historical archive than SPOT Has visible blue & thermal band (SPOT does not) larger area coverage and less cost (free) /area (than SPOT) SPOT HRV Improved geometric quality (along track scanner, but Landsat 8 OLI now has along track scanning) off-nadir viewing (stereo possible) and more frequent revisit than Landsat Better spatial (5m -Pan and 10m Multispectral) than Landsat NOAA AVHRR and MODIS Huge area covered, twice daily repeat coverage, better temporal resolution than Landsat or SPOT MODIS at 1000m has highest spectral resolution (36 bands) regional applications and global vegetation monitoring May be too coarse for many applications but free data