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.
The 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 the 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.
The National Landsat Archive Production System (NLAPS) is the Landsat processing system used for Landsat 1-5 MSS and Landsat 4 TM data.
The NLAPS system is able to “produce systematically-corrected, and terrain corrected products. . .” (United States Geological Survey, n.d.).
3 0.63 to 0.69 μm 30
4 0.76 to 0.90 μm 30
5 1.55 to 1.75 μm 30
6 10.4 to 12.5 μm 60
7 2.08 to 2.35 μm 30
Panchromatic (8) 0.50 to 0.90 μm 15
Band Number Wavelength
(microns) Resolution (m)
Landsat data received from satellites is generated into TM corrected data using the 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 the USGS, the 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 the TIROS-N in 1978.
Since the TIROS-N, many additional NOAA satellites have been launched and some continue to gather data.
AVHRR
The Advanced Very High Resolution Radiometer (AVHRR) is an optical multispectral scanner flown aboard National Oceanic and Atmospheric Administration (NOAA) orbiting satellites.
The AVHRR sensor provides pole to pole on-board collection of data.
The 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.
The 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.
The basic formats for AVHRR data 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).
The USGS also provides a series of derived AVHRR Normalized Difference Vegetation Index (NDVI) Composites and Global Land Cover Characterization (GLCC) data.
The 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 evalution.
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
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 on page 127 for information on the types of NOAA data available.
Use the Import/Export 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.The OrbView-3 mission began in 2003 with the satellite’s launch and the mission is complete.
The 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.
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: ORBIMAGE, 1999; ORBIMAGE, 2000
QuickBird
The 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.
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
Table 13: 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.The 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 Geo-corrected (Level 2A) -- geo-corrected with radiometric and geometric corrections and aligned to a map projection
• RapidEye Ortho (Level 3A) -- orthorectified with radiometric, geometric, and terrain corrections and aligned to a map projection
Table 14: 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) Image Capture Capacity 4 million sq km per day
Source: RapidEye AG, 2008 and RapidEye AG, 2009.
SeaWiFS
The Sea-viewing Wide Field-of-View Sensor (SeaWiFS) instrument is on-board the SeaStar spacecraft, which was launched in 1997. The 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. The ACS also provides attitude information within one SeaWiFS pixel.The SeaWiFS instrument is made up of an optical scanner and an electronics module. The swath width is 2,801 km LAC/HRPT (958.3 degrees) and 1,502 km GAC (45 degrees). The spatial resolution is 1.1 km LAC and 4.5 km GAC. The revisit time is one day.
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 the French Centre National d’Etudes Spatiales (CNES) and launched in early 1986. SPOT 2 satellite, launched in 1990, 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).Dynamic Range 12 bit
Table 14: RapidEye Characteristics
Band Wavelength (nanometers)
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
The sensors operate 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 pushes 3000/6000 sensors along its orbit. This is different from Landsat which scans with 16 detectors perpendicular to its orbit.
The SPOT satellite can observe the same area on the globe once every 26 days. The SPOT scanner normally produces nadir views, but it does 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.
The width of the swath observed varies 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—0.51 to 0.73 μm—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
(microns) Comments
1, Green 0.50 to 0.59 μm This band corresponds to the green reflectance of healthy vegetation.
2, Red 0.61 to 0.68 μm This band is useful for discriminating between plant species. It is also useful for soil
boundary and geological boundary delineations.
3,
Reflec-tive IR
0.79 to 0.89 μm This band is especially responsive to the amount of vegetation biomass present in a scene. It is useful for crop identification and emphasizes soil/crop and land/water contrasts.
Figure 25: SPOT Panchromatic vs. SPOT XS
See Ordering Raster Data on page 127 for information on the types of SPOT data available.
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 on page 121 and "Terrain Analysis" on page 645 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
The 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 Panchromatic vs XS
1 band
3 bands
1 pixel=
20x20m 1 pixel=
10x10m
Panchromatic
XS
radiometric resolution 0-255
The SPOT 4 satellite orbits the Earth at 822 km at the Equator. The 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.
Source: SPOT Image, 1998; SPOT Image, 1999; Center for Health Applications of Aerospace Related Technologies, 2000c.
SPOT 5
The 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 the VEGETATION 2 instrument on SPOT 4.
Source: Spot series, 2006.
WorldView-1
The 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.
The 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
Band Wavelength
1, Green 0.50 to 0.59 μm
2, Red 0.61 to 0.68 μm
3, (near-IR) 0.78 to 0.89 μm
4, (mid-IR) 1.58 to 1.75 μm
Panchromatic 0.61 to 0.68 μm
• Stereo area - 30 km x 110 km
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.
The WorldView-2 collection scenarios are: long strip, large area collect, multiple point targets, and stereo area collect.
Table 15: 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, 2010 and Padwick, et al, 2010.