Optical Satellite Data

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There are several data acquisition options available including photography, aerial sensors, and sophisticated satellite scanners. However, a satellite system offers these advantages:

  • Digital data gathered by a satellite sensor can be transmitted over radio or microwave communications links and stored on servers, DVDs, CDs, or magnetic tapes, so they are easily processed and analyzed by a computer.
  • Many satellites orbit the Earth, so the same area can be covered on a regular basis for change detection.
  • Once the satellite is launched, the cost for data acquisition is less than that for aircraft data.
  • Satellites have very stable geometry, meaning that there is less chance for distortion or skew in the final image.

SHARED Tip There are two types of satellite data access: direct access to many raster data formats for using files in their native format, and Import and Export functions for data exchange.

Satellite System

A satellite system is composed of a scanner with sensors and a satellite platform. Sensors are made up of detectors.

  • Scanner is the entire data acquisition system, such as Landsat TM scanner or SPOT panchromatic scanner (Lillesand and Kiefer, 1987). It includes the sensor and the detectors.
  • A sensor is a device that gathers energy, converts it to a signal, and presents it in a form suitable for obtaining information about the environment (Colwell, 1983).
  • A detector is the device in a sensor system that records electromagnetic radiation. For example, in the sensor system on the Landsat TM scanner there are 16 detectors for each wavelength band (except band 6, which has 4 detectors).

In a satellite system, the total width of the area on the ground covered by the scanner is called swath width, or width of total field of view (FOV). FOV differs from IFOV in that IFOV is a measure of the field of view of each detector. FOV is a measure of the field of view of all the detectors combined.

Satellite Characteristics

U. S. Landsat and the French SPOT satellites are two important data acquisition satellites. Landsat and SPOT satellites have several characteristics in common:

  • Both scanners can produce nadir views. Nadir is the area on the ground directly beneath the scanner’s detectors.
  • They have sun-synchronous orbits, meaning that they rotate around the Earth at the same rate as the Earth rotates on its axis, so data are always collected at the same local time of day over the same region.
  • They both record electromagnetic radiation in one or more bands. Multiband data are referred to as multispectral imagery. Single band, or monochrome, imagery is called panchromatic.

The current SPOT system has the ability to collect off-nadir stereo imagery.

Image Data Comparison

The figure below shows a comparison of the electromagnetic spectrum recorded by Landsat TM, Landsat MSS, SPOT, and National Oceanic and Atmospheric Administration (NOAA) AVHRR data. These data are described in detail in the following sections.

Multispectral Imagery Comparison

image_data_comparison_landsat_spot

ALI

Advanced Land Imager is one of three instruments onboard the Earth Observing 1 (EO-1) satellite, operated by NASA’s Goddard Space Flight Center. EO-1 was launched in November 2000, and carries the ALI, Hyperion, and LEISA Atmospheric Corrector (LAC) instruments.

These instruments collect multispectral and hyperspectral imagery in coordination with Landsat 7 Enhanced Thematic Mapper (ETM+).

EO-1 ALI consists of a 15° Wide Field Telescope (WFT) and partially populated focal plane occupying 1/5th of field-of-view, giving a ground swath width of 37 km. Operating in a pushbroom fashion at an orbit of 705 km, ALI provides Landsat type panchromatic and multispectral bands. These bands have been designed to mimic six Landsat bands with three additional bands.

ALI Sensor Characteristics

Wavelength

433 - 453 nm

450 - 515 nm

525 - 605 nm

630 - 690 nm

775 - 805 nm

845 - 890 nm

1200 - 1300 nm

1550 - 1750 nm

2080 - 2350 nm

Wavelength - Pan

480 - 690 nm

Spatial Resolution

30m (MS); 10m (Pan)

Swath Width

7.7 km

Source: National Aeronautics and Space Administration, 2009.

ALOS

Advanced Land Observing Satellite mission (ALOS) is a project operated by Japan Aerospace Exploration Agency (JAXA). ALOS was launched from Tanegashima Space Center in Japan in 2006.

Used for cartography, regional observation, disaster monitoring, and resource surveying, ALOS enhances land observing technology of its predecessors JERS-1 and ADEOS.

ALOS orbits at an altitude of 691 kilometers at an inclination of 98 degrees. Orbit is sun-synchronous sub-recurrent, and the repeat cycle is 46 days with a sub cycle of 2 days.

ALOS has three remote-sensing instruments: Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) for digital elevation mapping, Advanced Visible and Near Infrared Radiometer type 2 (AVNIR-2) for land coverage observation, and Phased Array type L-band Synthetic Aperture Radar (PALSAR) for all-weather, day and night land observation.

Source: Japan Aerospace Exploration Agency, 2003.

ALOS remote-sensing instruments are discussed in ALOS AVNIR-2, ALOS PALSAR, and ALOS PRISM in this topic.

ALOS AVNIR-2

AVNIR-2, Advanced Visible and Near Infrared Radiometer type 2, is a visible and near infrared radiometer on board ALOS satellite mission, launched in 2006. AVNIR-2 provides better spatial land-coverage maps and land-use classification maps for monitoring regional environments.

AVNIR-2 Sensor Characteristics

Number of Bands

4

Wavelength

Band 1: 420 to 500 nm

Band 2: 520 to 600 nm

Band 3: 610 to 690 nm

Band 4: 760 to 890 nm

Spatial Resolution

10 m (at Nadir)

Swath Width

70 km (at Nadir)

Number of Detectors

7000 per band

Pointing Angle

- 44 to + 44 degrees

Bit Length

8 bits

Source: Japan Aerospace Exploration Agency, 2007.

ALOS PRISM

PRISM, Panchromatic Remote-sensing Instrument for Stereo Mapping, is a panchromatic radiometer on board ALOS satellite mission, launched in 2006. The radiometer has 2.5m spatial resolution at nadir and its extracted data provides digital surface models.

PRISM has three independent optical systems for viewing nadir, forward, and backward, producing a stereoscopic image along the satellite’s track. The nadir-viewing telescope covers a width of 70 km, and the forward and backward viewing telescopes each cover 35 km.

PRISM’s wide field of view (FOV) provides three fully overlapped stereo images of a 35 km width without mechanical scanning or yaw steering of the satellite.

PRISM Sensor Characteristics

Number of Bands

1 (panchromatic)

Wavelength

520 to 770 nm

Number of Optics

3 (Nadir, Forward, Backward)

Base-to-Height Ratio

1.0 (between Forward and Backward view)

Spatial Resolution

2.5 m (at Nadir)

Swath Width

70 km (Nadir only)

35 km (Triplet mode)

Pointing Angle

-1.5 to +1.5 degrees

(Triplet mode, Cross-track direction)

Bit Length

8 bits

Source: Japan Aerospace Exploration Agency, 2003c.

ASTER

ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) is an instrument flying on Terra, a satellite launched in December 1999 as part of NASA’s Earth Observing System (EOS). ASTER is a cooperative effort between NASA, Japan’s Ministry of Economy, Trade and Industry (METI), and Japan’s Earth Remote Sensing Data Analysis Center (ERSDAC). Compared with Landsat Thematic Mapper and Japan’s JERS-1 OPS scanner, ASTER instrument is the next generation in remote sensing imaging.

ASTER captures high resolution data in the visible to thermal infrared wavelength spectrum and provides stereo viewing capability for DEM creation.

ASTER instrument consists of three subsystems: Visible and Near Infrared (VNIR), Shortwave Infrared (SWIR), and Thermal Infrared (TIR).

ASTER Sensor Characteristics

Characteristic

VNIR

SWIR

TIR

Spectral Range

Wavelengths in micrometres

Band 1

0.52 - 0.60

Band 4

1.68 - 1.70

Band 10

8.125 - 8.475

Band 2

0.63 - 0.69

Band 5

2.145 - 2.185

Band 11

8.475 - 8.825

Band 3

0.76 - 0.86

Band 6

2.185 - 2.225

Band 12

8/925 - 9.275

Band 3

0.76 - 0.86

Band 7

2.235 - 2.285

Band 13

10.25 - 10.95

Band 8

2.295 - 2.365

Band 14

10.95 - 11.65

Band 9

2.360 - 2.430

Ground Resolution

15 m

30 m

90 m

Swath Width

60 km

60 km

60 km

Source: National Aeronautics and Space Administration, 2004.

DEIMOS-1

DEIMOS-1 satellite, launched in July 2009, was developed by Deimos Imaging of Spain, and is based on a platform developed by SSTL (Surrey Satellite Technology Ltd).

Due to its large swath and less than 3 days of revisit time, DEIMOS-1 is suited for applications addressing rapid evolution of phenomena (vegetation, emergencies, and so forth).

DEIMOS-1 is one of the satellites comprising the international constellation DMC (Disaster Monitoring Constellation), containing satellites from UK, China, Nigeria, Spain, and Algeria.

DEIMOS-1 Sensor Characteristics

Number of Bands

3

Wavelengths

Near Infrared, Red, Green

Spatial Resolution

22 m

Swath Width

630 km

Source: Deimos Engenharia, 2011.

EROS A and EROS B

The first Earth Remote Observation Satellite (EROS A), launched in December 2000, was developed by ImageSat International N.V. They subsequently launched their second satellite, EROS B, in April 2006. ImageSat International N.V. is a Netherlands Antilles company with offices in Cyprus and Israel.

EROS A imaging techniques offer panchromatic images in basic type and as stereo pairs. EROS B imaging techniques offer panchromatic images in basic, stereo pair, triplet, and mosaic types.

EROS Sensor Characteristics

Characteristic

EROS A

EROS B

Geometry of orbit

sun-synchronous

sun-synchronous

Orbit Altitude

~ 500 km

~ 500 km

Swath Width

14 km at nadir

7 km at nadir

Ground Sampling Distance

1.9 m at nadir from 510 km

0.7 m at nadir from 510 km for TDI stages 1,4,8

0.8 m at nadir from 510 km for all other TDI stages

Spectral Bandwidth

0.5 to 0.9

0.5 to 0.9

Source: ImageSat International N.V. 2008.

FORMOSAT-2

FORMOSAT-2 satellite, launched in May 2004, was the first remote sensing satellite developed by National Space Organization (NSPO). The main mission of FORMOSAT-2 is to capture satellite images of Taiwan island and surrounding oceanic regions, and terrestrial and oceanic regions of the entire Earth.

FORMOSAT-2 onboard sensors include a Remote Sensing Instrument and ISUAL (Imager of Sprites and Upper Atmospheric Lightning).

FORMOSAT-2 Characteristics

Geometry of orbit

sun-synchronous

Orbit Altitude

891 km

Swath Width

24 km

Sensor Resolution

panchromatic - 2 m

multispectral - 8 m

Source: National Space Organization, 2008 and European Space Agency, 2010b.

GeoEye-1

GeoEye-1 satellite, launched in 2008, was developed by GeoEye, a company formed through the combination of ORBIMAGE and Space Imaging. GeoEye-1 orbits at an altitude of 681 km, or 423 miles in a sun-synchronous orbit type.

GeoEye-1 data collection capacity is up to 700,000 square km per day of pan area and up to 350,000 square km per day of pan-sharpened multispectral area.

GeoEye-1 Characteristics

Geometry of orbit

sun-synchronous

Orbit Altitude

681 km

Orbit Inclination

98 degrees

Swath Width

15.2 km at nadir

Area Size - single point

225 sq km (15 km x 15 km)

Area Size - large area

15,000 sq km (300 km x 50 km)

Area Size - cell size

10,000 sq km (100 km x 100 km)

Area Size - stereo area

6,270 sq km (224 km x 28 km)

Sensor Resolution

nominal at Nadir

panchromatic - 0.41 m (1.34 feet)

multispectral - 1.65 m (5.41 feet)

Spectral Bandwidth

Panchromatic

459 to 800 nm

Spectral Bandwidth

Multispectral

450 - 510 nm (blue)

510 - 580 nm (green)

655 - 690 nm (red)

780 - 920 nm (near infrared)

Source: GeoEye, 2008.

IKONOS

IKONOS satellite was launched in September 1999.

The panchromatic sensor resolution is 1 m, and multispectral scanner resolution is 4 m. The swath width is 13 km at nadir. Accuracy with out ground control is 12 m horizontally, and 10 m vertically; with ground control it is 2 m horizontally, and 3 m vertically.

IKONOS orbits at an altitude of 423 miles, or 681 kilometers. Revisit time is 2.9 days at 1 m resolution, and 1.5 days at 1.5 m resolution.

IKONOS Characteristics

Band

Wavelength

(micrometres)

1, Blue

0.45 to 0.52

2, Green

0.52 to 0.60

3, Red

0.63 to 0.69

4, NIR

0.76 to 0.90

Panchromatic

0.45 to 0.90

Source: Space Imaging, 1999a; Center for Health Applications of Aerospace Related Technologies, 2000a.

IRS-1C, IRS-1D

IRS-1C satellite, developed by Indian Space Research Organisation, was launched in December 1995. ISRO announced mission complete in September 2007.

IRS-1D, launched in September 1997, was developed by Indian Space Research Organisation. ISRO announced mission complete in January 2010.

Imagery collected by IRS-1D is distributed in black and white format. The panchromatic imagery "reveals objects on the Earth’s surface (such) as transportation networks, large ships, parks and opens space, and built-up urban areas" (Space Imaging, 1999b). This information can be used to classify land cover in applications such as urban planning and agriculture.

IRS-1C and IRS-1D carried these sensors on board:

LISS-III

LISS-III had spatial resolution of 23 m, with the exception of the SW Infrared band, which was 70 m. Bands 2, 3, and 4 had swath width of 142 kilometers; band 5 had swath width of 148 km.

Band

Wavelength

(micrometres)

1, Blue

---

2, Green

0.52 to 0.59

3, Red

0.62 to 0.68

4, NIR

0.77 to 0.86

5, SW IR

1.55 to 1.70

Source: National Remote Sensing Agency, 1998.

Panchromatic Sensor

The panchromatic sensor had 5.8 m spatial resolution, as well as stereo capability. Its swath width is 70 m. Revisit time was every five days, with ± 26° off-nadir viewing.

Band

Wavelength

(micrometres)

Pan

0.5 to 0.75

Wide Field Sensor (WiFS)

WiFS had 188 m spatial resolution, and repeat coverage every five days at the Equator. Swath width was 774 km.

Band

Wavelength

(micrometres)

1, Red

0.62 to 0.68

2, NIR

0.77 to 0.86

3, MIR

1.55 to 1.75

Source: Space Imaging, 1999b; Center for Health Applications of Aerospace Related Technologies, 1998; ISRO, 2013.

KOMPSAT 1-2

Korea Aerospace Research Institute (KARI) has developed KOMPSAT-1 (KOrea Multi-Purpose SATellite) and KOMPSAT-2 satellite systems for surveillance of large scale disasters, acquisition of high resolution images for GIS, and composition of printed and digitized maps.

KOMPSAT-1, launched in December 1999, carries an Electro-Optical Camera (EOC) sensor and KOMPSAT-2, launched in July 2006, carries a Multi-Spectral Camera (MSC) sensor.

Through a third party mission agreement, European Space Agency makes a sample dataset of European cities available from these missions.

KOMPSAT Characteristics

Characteristic

KOMPSAT-1

KOMPSAT-2

Geometry of orbit

sun-synchronous circular polar

sun-synchronous circular

Orbit Altitude

685 km

685 km

Swath Width

24 km EOC

~ 15 km

Resolution

6 m EOC

1 m panchromatic

4 m multispectral

Spectral Bandwidth

500 - 900 nm panchromatic

450 - 900 nm multispectral (4 bands)

Source: European Space Agency, 2010c.

Landsat 1-5

In 1972, National Aeronautics and Space Administration (NASA) initiated the first civilian program specializing in the acquisition of remotely sensed digital satellite data. The first system was called ERTS (Earth Resources Technology Satellites), and later renamed to Landsat. There have been several Landsat satellites launched since 1972. Landsats 1, 2, 3 and 4 are no longer operating. US Geological Survey Flight Operations Team completed decommission of Landsat 5 in June 2013.

Landsats 1, 2, and 3 gathered Multispectral Scanner (MSS) data and Landsats 4 and 5 collected MSS and TM data. MSS and TM are discussed in more detail in the following sections.

Landsat data are available from EROS Data Center. See Ordering Raster Data for more information.

Source: United States Geological Survey, 2013.

MSS

Multispectral Scanner from Landsats 4 and 5 had a swath width of approximately 185 × 170 km from a height of approximately 900 km for Landsats 1, 2, and 3, and 705 km for Landsats 4 and 5. MSS data are widely used for general geologic studies as well as vegetation inventories.

Spatial resolution of MSS data is 56 × 79 m, with a 79 × 79 m IFOV. A typical scene contains approximately 2340 rows and 3240 columns. Radiometric resolution is 6-bit, but it is stored as 8-bit (Lillesand and Kiefer, 1987).

Detectors record electromagnetic radiation (EMR) in four bands:

  • Bands 1 and 2 are in the visible portion of the spectrum and can detect cultural features, such as roads. These bands also show detail in water.
  • Bands 3 and 4 are in the near-infrared portion of the spectrum and can be used to identify land, water, and vegetation.

Band

Wavelength

(micrometres)

Uses

1, Green

0.50 to 0.60

Scans the region between blue and red chlorophyll absorption bands.

Green reflectance of healthy vegetation.

Map water bodies.

2, Red

0.60 to 0.70

Red chlorophyll absorption band of healthy green vegetation.

Identify vegetation types.

Determine soil boundary and geological boundary delineations

Cultural features.

3, Red, NIR

0.70 to 0.80

Identify crops.

Identify soil and crop boundaries.

Identify land and water boundaries.

4, NIR

0.80 to 1.10

Vegetation surveys.

Penetrates atmospheric haze (Jensen, 1996).

Source: Center for Health Applications of Aerospace Related Technologies, 2000b.

TM

TM scanner was a multispectral scanning system much like the MSS, except that the TM sensor records reflected and emitted electromagnetic energy from the visible, reflective-infrared, middle-infrared, and thermal-infrared regions of the spectrum. TM had higher spatial, spectral, and radiometric resolution than MSS.

TM had a swath width of approximately 185 km from a height of approximately 705 km. It is useful for vegetation type and health determination, soil moisture, snow and cloud differentiation, rock type discrimination, and so forth.

Spatial resolution of TM is 28.5 × 28.5 m for all bands except the thermal (band 6), which has a spatial resolution of 120 × 120 m. The larger pixel size of this band is necessary for adequate signal strength. However, the thermal band is resampled to 28.5 × 28.5 m to match the other bands. Radiometric resolution is 8-bit, meaning that each pixel has a possible range of data values from 0 to 255.

Detectors recorded EMR in seven bands:

  • Bands 1, 2, and 3 are in the visible portion of the spectrum and are useful in detecting cultural features such as roads. These bands also show detail in water.
  • Bands 4, 5, and 7 are in the reflective-infrared portion of the spectrum and can be used to differentiate between land and water.
  • Band 6 is in the thermal portion of the spectrum and is used for thermal mapping (Jensen, 1996; Lillesand and Kiefer, 1987).

Band

Wavelength

(micrometres)

Uses

1, Blue

0.45 to 0.52

Coastal water area mapping.

Differentiate between soil and vegetation.

Forest type mapping.

Detect cultural features.

2, Green

0.52 to 0.60

Green reflectance of healthy vegetation.

Identify cultural features.

3, Red

0.63 to 0.69

Differentiate between many plant species.

Determine soil boundary and geological boundaries.

Identify cultural features.

4, NIR

0.76 to 0.90

Determine amount of vegetation biomass.

Identify crops.

Determine soil and crop boundaries.

Determine land and water boundaries.

5, MIR

1.55 to 1.75

Measure moisture content in plants for crop drought studies and plant health analyses.

Differentiate between clouds, snow, and ice.

6, TIR

10.40 to 12.50

Detect stress in vegetation and crops.

Measure heat intensity.

Determine insecticide applications.

Locate thermal pollution.

Locate geothermal activity.

7, MIR

2.08 to 2.35

Determine boundaries of geologic rock type and soil.

Measure soil and vegetation moisture content.

Source: Center for Health Applications of Aerospace Related Technologies, 2000b.

Landsat MSS vs. Landsat TM

landsat_mms_tm_bands_diagram

Band Combinations for Displaying TM Data

Different combinations of TM bands can be displayed to create different composite effects. The following combinations are commonly used to display images:

The order of the bands corresponds to Red, Green, and Blue (RGB) color channels of the monitor.

  • Bands 3, 2, 1 create a true color composite. True color means that objects look as they would to the naked eye—similar to a color photograph.
  • Bands 4, 3, 2 create a false color composite. False color composites appear similar to an infrared photograph where objects do not have the same colors or contrasts as they would naturally. For instance, in an infrared image, vegetation appears red, water appears navy or black, and so forth.
  • Bands 5, 4, 2 create a pseudo color composite. (A thematic image is also a pseudo color image.) In pseudo color, the colors do not reflect the features in natural colors. For instance, roads may be red, water yellow, and vegetation blue.

Different color schemes can be used to bring out or enhance the features under study. These are by no means all of the useful combinations of these seven bands. The bands to be used are determined by the particular application.

See Image Display for more information on how images are displayed, and Enhancement for more information on how images can be enhanced.

Landsat 7

Landsat 7 satellite, launched in 1999, uses Enhanced Thematic Mapper Plus (ETM+) to observe the Earth. Capabilities new to Landsat 7 include the following:

  • 15m spatial resolution panchromatic band
  • 5% radiometric calibration with full aperture
  • 60m spatial resolution thermal IR channel

The primary receiving station for Landsat 7 data is located in Sioux Falls, South Dakota at USGS EROS Data Center (EDC). ETM+ data is transmitted using X-band direct downlink at a rate of 150 Mbps. Landsat 7 is capable of capturing scenes without cloud obstruction, and the receiving stations can obtain this data in real time using X-band. Stations located around the globe, however, are only able to receive data for the portion of the ETM+ ground track where the satellite can be seen by the receiving station.

Landsat 7 Data Types

One type of data available from Landsat 7 is browse data. Browse data is "a lower resolution image for determining image location, quality and information content." The other type of data is metadata, which is "descriptive information on the image." This information is available using the internet within 24 hours of being received by the primary ground station. Moreover, EDC processes the data to Level 0r. This data has been corrected for scan direction and band alignment errors only. Level 1G data, which is corrected, is also available.

Landsat 7 Specifications

Information about spectral range and ground resolution of the bands of the Landsat 7 satellite is provided in the following table:

Band Number

Wavelength (micrometres)

Resolution (m)

1

0.45 - 0.52

30

2

0.52 - 0.60

30

3

0.63 - 0.69

30

4

0.76 - 0.90

30

5

1.55 - 1.75

30

6

10.4 - 12.5

60

7

2.08 - 2.35

30

8 - Panchromatic

0.50 - 0.90

15

Landsat 7 has a swath width of 185 kilometers. Repeat coverage interval is 16 days, or 233 orbits. The satellite orbits the Earth at 705 kilometers.

Source: National Aeronautics and Space Administration, 1998; National Aeronautics and Space Administration, 2001.

Landsat 8

Landsat 8, launched in 2013, flies in an 8-day offset from Landsat 7. Landsat 8 carries two instruments; Operational Land Imager (OLI) and Thermal Infrared Sensor (TIRS). The OLI captures three additional bands: coastal blue and aerosol studies band, cirrus cloud detection band, and a quality assessment band. TIRS provides two thermal bands compared to one thermal band in previous Landsat sensors.

Band wavelengths and combinations are different in Landsat 8 than Landsat 7 or 5 data. For example, Band 2 is green in Landsat 7, but in Landsat 8, Band 3 is the green wavelength.

Band Number

Wavelength (micrometres)

Resolution (m)

1 - Coastal aerosol

0.43 - 0.45

30

2 - Blue

0.45 - 0.51

30

3 - Green

0.53 - 0.59

30

4 - Red

0.64 - 0.67

30

5 - Near Infrared

0.85 - 0.88

30

6 - SWIR 1

1.57 - 1.65

60

7 - SWIR 2

2.11 - 2.29

30

8 - Panchromatic

0.50 to 0.68

15

9 - Cirrus cloud

1.36 - 1.38

30

10 - Thermal Infrared 1

10.60 - 11.19

100

11 - Thermal Infrared 2

11.50 - 12.51

100

Source: United States Geological Survey, 2013a.

LPGS and NLAPS Processing Systems

There are two processing systems used to generate Landsat MSS, TM, and ETM+ data products. The products generated by LPGS and NLAPS are mostly similar, but there are considerable differences.

Level 1 Product Generation System (LPGS) is for Landsat 7 ETM+ and Landsat 5 TM data.

The levels of processing are:

  • Level 1G (radiometrically and geometrically corrected - MSS, TM and ETM+)
  • Level 1P (systematically terrain corrected - TM and MSS only)
  • Level 1Gt (systematically terrain corrected - TM and ETM+ only)
  • Level 1T (terrain corrected - MSS, TM and ETM+)

There are geometric differences, radiometric differences, and data format differences between LPGS and NLAPS processing systems. Details of the differences are listed on the United States Geological Survey - Landsat Missions web site.

Source: United States Geological Survey (USGS) 2008.

National Landsat Archive Production System (NLAPS) is the Landsat processing system used for Landsat 1-5 MSS and Landsat 4 TM data.

NLAPS system is able to "produce systematically-corrected, and terrain corrected products. . ." (United States Geological Survey, n.d.).

Landsat data received from satellites is generated into TM corrected data using NLAPS by:

  • correcting and validating the mirror scan and payload correction data
  • providing for image framing by generating a series of scene center parameters
  • synchronizing telemetry data with video data
  • estimating linear motion deviation of scan mirror/scan line corrections
  • generating benchmark correction matrices for specified map projections
  • producing along- and across-scan high-frequency line matrices

According to USGS, products provided by NLAPS include the following:

  • image data and the metadata describing the image
  • processing procedure, which contains information describing the process by which the image data were produced
  • DEM data and the metadata describing them (available only with terrain corrected products)

Source: United States Geological Survey, n.d.

NOAA Polar Orbiter Data

NOAA has sponsored several polar orbiting satellites to collect data of the Earth. These satellites were originally designed for meteorological applications, but the data gathered have been used in many fields—from agronomy to oceanography (Needham, 1986).

The first of these satellites to be launched was TIROS-N in 1978. Since TIROS-N, many additional NOAA satellites have been launched and some continue to gather data.

AVHRR

Advanced Very High Resolution Radiometer (AVHRR) is an optical multispectral scanner flown aboard National Oceanic and Atmospheric Administration (NOAA) orbiting satellites.

AVHRR sensor provides pole to pole on-board collection of data. Swath width is 2399 km (1491 miles) and the satellites orbit the Earth 14 times each day at an altitude of 833 km (517 miles).

Source: United States Geological Survey, 2006a.

AVHRR system allows for direct transmission in real-time of data called High Resolution Picture Transmission (HRPT). It also allows for about ten minutes of data to be recorded over any portion of the world on two recorders on board the satellite. These recorded data are called Local Area Coverage (LAC). LAC and HRPT have identical formats; the only difference is that HRPT are transmitted directly and LAC are recorded.

AVHRR data formats which can be imported into ERDAS IMAGINE are:

  • LAC—(Local Area Coverage) data recorded on board the sensor with a spatial resolution of approximately 1.1 × 1.1 km
  • HRPT—(High Resolution Picture Transmission) direct transmission of AVHRR data in real-time with the same resolution as LAC
  • GAC—(Global Area Coverage) data produced from LAC data by using only 1 out of every 3 scan lines. GAC data have a spatial resolution of approximately 4 × 4 km

AVHRR data are available in 10-bit packed and 16-bit unpacked format. The term packed refers to the way in which the data are written to the tape. Packed data are compressed to fit more data on each tape (Kidwell, 1988).

USGS also provides a series of derived AVHRR Normalized Difference Vegetation Index (NDVI) Composites and Global Land Cover Characterization (GLCC) data.

AVHRR data collection effort provides cloud mapping, land-water boundaries, snow and ice detection, temperatures of radiating surfaces and sea surface temperatures. This data is also useful for vegetation studies, land cover mapping, country maps, continental maps, world maps, and snow cover evaluation.

AVHRR Data Characteristics

Band

Wavelength (micrometres)

NOAA 6,8,10

Wavelength (micrometres)

NOAA 7,9,11,12, 14

Wavelength (micrometres)

NOAA 15,16,17

Primary Uses

1

0.58 - 0.68

0.58 - 0.68

0.58 - 0.68

Daytime cloud/surface and vegetation mapping

2

0.725 - 1.10

0.725 - 1.10

0.725 - 1.10

Surface water, ice, snow melt, and vegetation mapping

3A

1.58 - 1.64

Snow and ice detection

3B

3.55 - 3.93

3.55 - 3.93

3.55 - 3.93

Sea surface temperature, night-time cloud mapping

4

10.50 - 11.50

10.3 - 11.3

10.3 - 11.3

Sea surface temperature, day and night cloud mapping

5

Band 4 repeated

11.5 - 12.5

11.5 - 12.5

Sea surface temperature, day and night cloud mapping

Source: United States Geological Survey, 2006a.

AVHRR data have a radiometric resolution of 10-bits, meaning that each pixel has a possible data file value between 0 and 1023. AVHRR scenes may contain one band, a combination of bands, or all bands. All bands are referred to as a full set, and selected bands are referred to as an extract.

See Ordering Raster Data for information about NOAA data.

SHARED Tip Use Import function to import AVHRR data.

OrbView-3

OrbView-3 was built for Orbital Imaging Corporation (now GeoEye) and was designed to provide high-resolution imagery.

OrbView-3 mission began in 2003 with the satellite’s launch and the mission is complete.

OrbView-3 satellite provided both 1 meter panchromatic imagery and 4 meter multispectral imagery of the entire Earth. The satellite orbit was 470 km inclined at 97 degrees/470 km and sun-synchronous, with a swath width of 8 km.

Source: Orbital Sciences Corporation, 2008.

Orbital Imaging Corporation plans were for "One-meter imagery will enable the viewing of houses, automobiles and aircraft, and will make it possible to create highly precise digital maps and three-dimensional fly-through scenes. Four-meter multispectral imagery will provide color and infrared information to further characterize cities, rural areas and undeveloped land from space" (ORBIMAGE, 1999). Specific applications include telecommunications and utilities, agriculture and forestry.

Bands

Spectral Range

1

450 to 520 nm

2

520 to 600 nm

3

625 to 695 nm

4

760 to 900 nm

Panchromatic

450 to 900 nm

Source: ORBIMAGE, 1999; ORBIMAGE, 2000.

Pleiades

Pleiades-1A satellite, launched in 2011, is the first very high-resolution satellite from SPOT. The satellite is capable of providing orthorectified color data at 0.5-meter resolution and revisiting any point on Earth as it covers a total of 1 million square kilometers (approximately 386,102 square miles) daily. Pleiades-1A is capable of acquiring high-resolution stereo imagery in just one pass, and can accommodate large areas (up to 1,000 km x 1,000 km).

The satellite features four spectral bands (blue, green, red, and IR), as well as image location accuracy of 3 meters (CE90) without ground control points. Image location accuracy can be improved even further—up to an exceptional 1 meter—by the use of GCPs.

Pleiades-1B satellite was launched in 2012, and is phased 180 degrees apart from Pleiades 1A.

Pleiades Characteristics

Imagery Products

50-cm black and white

50-cm color

2-meter multispectral

Bundle: 50-cm B&W and 2-meter multispectral

Spectral Bands

P: 480-830 nm

Blue: 430-550 nm

Green: 490-610 nm

Red: 600-720 nm

Near Infrared: 750-950 nm

Preprocessing Levels

Sensor

Ortho

Image Location Accuracy

With ground control points: 1m

Without ground control points: 3m (CE90)

Imaging Capacity

Daily constellation capacity: 1,000,000 sq.km

Strip mapping (mosaic): 100 km x 100 km

Stereo imaging: 20 km x 280 km

Max. spots over 100 km x 200 km: 30 (crisis mode)

Imaging Swath

20 km at nadir

Revisit Interval

Daily

Source: Satellite Imaging Corporation, 2013.

QuickBird

QuickBird satellite was launched in 2001 by DigitalGlobe offering imagery for map publishing, land and asset management, change detection and insurance risk assessment.

QuickBird produces sub-meter resolution panchromatic and multispectral imagery. The data collection nominal swath width is 16.5 km at nadir, and areas of interest sizes are 16.5 km x 16.5 km for a single area and 16.5 km x 115 km for a strip.

QuickBird Characteristics

Geometry of orbit

sun-synchronous

Orbit Altitude

450 km

Orbit Inclination

98 degrees

Swath Width

normal - 16.5 km at nadir

accessible ground - 544 km centered on the satellite ground track

Sensor Resolution

ground sample distance at nadir

panchromatic - 61 cm (2 feet)

multispectral - 2.4 m (8 feet)

Spectral Bandwidth

Panchromatic

445 to 900 nm

Spectral Bandwidth

Multispectral

450 - 520 nm (blue)

520 - 600 nm (green)

630 - 690 nm (red)

760 - 900 (near infrared)

Source: DigitalGlobe, 2008a.

RapidEye

The German company RapidEye AG launched a constellation of five satellite sensors in 2008. All five satellites contain equivalent sensors, are calibrated equally to one another, and are located in the same orbital plane. This allows RapidEye to deliver multi-temporal data sets in high resolution in near real-time.

RapidEye satellite system collects imagery in five spectral bands, and is the first commercial system to offer the Red-Edge band, which measures variances in vegetation, allowing for species separation and monitoring vegetation health.

RapidEye standard image products are offered at three processing levels:

  • RapidEye Basic (Level 1B) -- geometrically uncorrected, radiometric and sensor corrected
  • RapidEye Ortho (Level 3A) -- orthorectified with radiometric, geometric, and terrain corrections and aligned to a map projection

RapidEye Characteristics

Number of Satellites

5

Orbit Altitude

630 km in sun-synchronous orbit

Equator Crossing Time

11:00 am (approximately)

Sensor Type

Multi-spectral push broom imager

Spectral Bands

440 - 510 nm (Blue)

520 - 590 nm (Green)

630 - 685 nm (Red)

690 - 730 nm (Red Edge)

760 - 850 nm (Near IR)

Ground Sampling Distance (nadir)

6.5 m

Pixel Size (orthorectified)

5 m

Swath Width

77 km

Revisit Time

Daily (off-nadir) / 5.5 days (at nadir)

Dynamic Range

12 bit

Source: RapidEye AG, 2008 and RapidEye AG, 2009.

SeaWiFS

Sea-viewing Wide Field-of-View Sensor (SeaWiFS) instrument is on-board the SeaStar spacecraft, which was launched in 1997. SeaStar spacecraft’s orbit is circular, at an altitude of 705 km. The satellite uses an attitude control system (ACS), which maintains orbit, as well as performs solar and lunar calibration maneuvers. ACS also provides attitude information within one SeaWiFS pixel.

SeaWiFS instrument is made up of an optical scanner and an electronics module. Swath width is 2,801 km LAC/HRPT (958.3 degrees) and 1,502 km GAC (45 degrees). Spatial resolution is 1.1 km LAC and 4.5 km GAC. Revisit time is one day.

Band

Wavelength

1, Blue

402 to 422 nm

2, Blue

433 to 453 nm

3, Cyan

480 to 500 nm

4, Green

500 to 520 nm

5, Green

545 to 565 nm

6, Red

660 to 680 nm

7, NIR

745 to 785 nm

8, NIR

845 to 885 nm

Source: National Aeronautics and Space Administration, 1999; Center for Health Applications of Aerospace Related Technologies, 1998.

SPOT 1 -3

SPOT 1 satellite was developed by French Centre National d’Etudes Spatiales (CNES), launched in early 1986, and deorbited in 2003. SPOT 2 satellite, launched in 1990 and deorbited in 2009, was the first in the series to carry the DORIS precision positioning instrument. SPOT 3, launched in 1993, also carried the DORIS instrument, plus the American passenger payload POAM II, used to measure atmospheric ozone at the poles. SPOT 3 was decommissioned in 1996. (Spot series, 2006; Spot satellites, 2013).

The sensors operated in two modes, multispectral and panchromatic. SPOT is commonly referred to as a pushbroom scanner meaning that all scanning parts are fixed, and scanning is accomplished by the forward motion of the scanner. SPOT pushed 3000/6000 sensors along its orbit. This is different from Landsat which scans with 16 detectors perpendicular to its orbit.

SPOT satellite observed the same area on the globe once every 26 days. SPOT scanner normally produced nadir views, but it did have off-nadir viewing capability. Off-nadir refers to any point that is not directly beneath the detectors, but off to an angle. Using this off-nadir capability, one area on the Earth can be viewed as often as every 3 days.

This off-nadir viewing can be programmed from the ground control station, and is quite useful for collecting data in a region not directly in the path of the scanner or in the event of a natural or man-made disaster, where timeliness of data acquisition is crucial. It is also very useful in collecting stereo data from which elevation data can be extracted.

Width of the swath observed varied between 60 km for nadir viewing and 80 km for off-nadir viewing at a height of 832 km (Jensen, 1996).

Panchromatic

SPOT Panchromatic (meaning sensitive to all visible colors) has 10 × 10 m spatial resolution, contains 1 band—510 to 730 nm—and is similar to a black and white photograph. It has a radiometric resolution of 8 bits (Jensen, 1996).

XS

SPOT XS, or multispectral, has 20 × 20 m spatial resolution, 8-bit radiometric resolution, and contains 3 bands (Jensen, 1996).

Band

Wavelength

(micrometres)

Uses

1, Green

0.50 to 0.59

Green reflectance of healthy vegetation.

2, Red

0.61 to 0.68

Discriminates between plant species.

Soil boundary and geological boundary delineations.

3, Reflective IR

0.79 to 0.89

Measures amount of vegetation biomass present in a scene.

Crop identification.

Emphasizes contrasts between soil and crop, land and water.

SPOT Panchromatic vs. SPOT XS

spot_pan_xs_bands_diagram

See Ordering Raster Data for information on available SPOT data.

Stereoscopic Pairs

Two observations can be made by the panchromatic scanner on successive days, so that the two images are acquired at angles on either side of the vertical, resulting in stereoscopic imagery. Stereoscopic imagery can also be achieved by using one vertical scene and one off-nadir scene. This type of imagery can be used to produce a single image, or topographic and planimetric maps (Jensen, 1996).

Topographic maps indicate elevation. Planimetric maps correctly represent horizontal distances between objects (Star and Estes, 1990).

See Topographic Data and Terrain Analysis for more information about topographic data and how SPOT stereopairs and aerial photographs can be used to create elevation data and orthographic images.

SPOT 4

SPOT 4 satellite was launched in 1998. SPOT 4 carries High Resolution Visible Infrared (HR VIR) instruments that obtain information in the visible and near-infrared spectral bands.

SPOT 4 satellite orbits the Earth at 822 km at the Equator. SPOT 4 satellite has two sensors on board: a multispectral sensor, and a panchromatic sensor. The multispectral scanner has a pixel size of 20 × 20 m, and a swath width of 60 km. The panchromatic scanner has a pixel size of 10 × 10 m, and a swath width of 60 km.

Band

Wavelength

1, Green

500 to 590 nm

2, Red

610 to 680 nm

3, (near-IR)

780 to 890 nm

4, (mid-IR)

1580 to 1750 nm

Panchromatic

610 to 680 nm

Source: SPOT Image, 1998; SPOT Image, 1999; Center for Health Applications of Aerospace Related Technologies, 2000c.

SPOT 5

SPOT 5 satellite, launched in 2002, carries two new HRVIR viewing instruments which have a better resolution: 2.5 to 5 meters in panchromatic and infrared mode and 10 meters in multispectral mode.

SPOT 5 carries an HRS (High Resolution Stereoscopic) imaging instrument operating in panchromatic mode with multiple cameras. The forward-pointing camera acquires images of the ground, then the rearward-pointing camera covers the same strip 90 seconds later. Thus HRS is able to acquire stereopair images almost simultaneously to map relief, produce DEMs, and generate orthorectified products. SPOT 5 also carries VEGETATION 2 instrument, which offers a spatial resolution of one kilometer and a wide imaging swath. This instrument is identical to VEGETATION 2 instrument on SPOT 4.

Source: Spot series, 2006.

WorldView-1

WorldView-1 satellite was launched in 2007 by DigitalGlobe offering imagery for map creation, change detection and in-depth image analysis.

WorldView-1 produces half-meter resolution panchromatic imagery. The satellite has an average revisit time of 1.7 days and is capable of collecting up to 750,000 square kilometers (290,000 square miles) per day of half-meter imagery.

Data collection options include:

  • Long strip - 17.6 km x up to 330 km
  • Large area - 60 km x 110 km
  • Multiple point targets - up to 17.6 km
  • Stereo area - 30 km x 110 km

WorldView-1 Characteristics

Geometry of orbit

sun-synchronous

Orbit Altitude

496 km

Swath Width

17.6 km at nadir

Sensor Resolution

GSD = ground sample distance

0.50 meters GSD at nadir

0.59 meters GSD at 25° off-nadir

Spectral Bandwidth

Panchromatic

Source: DigitalGlobe, 2008b.

WorldView-2

Owned and operated by DigitalGlobe, WorldView-2 was launched in 2009 to provide highly detailed imagery for precise vector and terrain data creation, pan-sharpened imagery, change detection, and in-depth remote sensing image analysis. WorldView-2 is a panchromatic imaging system featuring half-meter resolution imagery, combined with a multispectral capability featuring two meter resolution imagery.

WorldView-2 multispectral capability provides 8 spectral bands, including 4 new colors: coastal blue, yellow, red edge, and near IR2.

  • Coastal blue is useful for bathymetric studies.
  • Yellow detects the "yellowness" of vegetation on land and in water.
  • Red edge measures plant health and is useful for vegetation classification.
  • Near Infrared 2 overlaps the Near IR1 band but is less affected by atmospheric influence and enables broader vegetation analysis.

WorldView-2 collection scenarios are: long strip, large area collect, multiple point targets, and stereo area collect.

WorldView-2 Characteristics

Sensor Bands

Pan: 450 - 800 nm

Multispectral (nm):

Coastal: 400 - 450

Blue: 450 - 510

Green: 510 - 580

Yellow: 585 - 625

Red: 630 - 690

Red Edge: 705 - 745

Near IR1: 770 - 895

Near IR2: 860 - 1040

Sensor Resolution

GSD = ground sample distance

Pan: 0.46 meters GSD at nadir

0.52 meters GSD at 20° off-nadir

Multi: 1.84 meters GSD at nadir

2.08 meters GSD at 20° off-nadir

Swath Width

16.4 km at nadir

Source: DigitalGlobe, 2010 and Padwick, et al, 2010.