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Please note that the machine on which these AVHRR data are processed has reached its life expectancy and will no longer be available as of 02 June 2008 until further notice. Thus, orders placed after 02 June 2008 will not be fulfilled. Please contact NSIDC User Services if you have questions or concerns regarding these data.
NSIDC collects and archives 1.1 km High Resolution Picture Transmission (HRPT) and Local Area Coverage (LAC) Advanced Very High Resolution Radiometer (AVHRR) imagery. Original data are from recorded and rebroadcast LAC images for both polar regions and from several HRPT receiving stations, including McMurdo, Palmer, Casey, Fairbanks, Prince Albert, and Tromsø. NSIDC receives these data from a polar subset of the Land Processes (LP) DAAC Global Land 1 km AVHRR Data Set and from the Scripps Institute of Oceanography, which collects Antarctic HRPT data from the McMurdo and Palmer stations. NSIDC received LAC data for the Southern Hemisphere through 1998 from a University of Colorado Domestic Satellite (DOMSAT) receiver and from the National Oceanic and Atmospheric Administration (NOAA) Satellite Active Archive (SAA) after 1998. These sources provide nearly complete coverage of sea ice, land ice, and polar land in the north and south polar regions, at 1.1 km resolution for all five bands of the AVHRR sensor. Data extend from April 1992 through the present for the Southern Hemisphere, and from August 1993 through the present for the Northern Hemisphere.
Archived scenes, browse imagery, and information on location, time of acquisition, image size, and data quality are available via the AVHRR Polar 1 Km Level 1B Data Set Product Web site.
1. Title
2. Investigator
3. Introduction
4. Theory of Measurements
5. Equipment (information in development)
6. Procedure
7. Observations (no information at this time)
8. Data Granularity
9. Data Description
10. Data Manipulations
11. Errors
12. Notes
13. Application of the Data Set
14. Data Set Plans
15. References
16. Related Software
17. Data Access
18. Output Products and Availability
19. Glossary of Acronyms
Data Set Identification: AVHRR Polar 1 km Level 1b Data Set
Creation Date: 22 February 1995
Revision Date: 17 July 2001
Ted Scambos
449 UCB, University of Colorado, Boulder, CO 80309-0449, USA
NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449 USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
e-mail: nsidc@nsidc.org
NSIDC archives polar images from AVHRR LAC and HRPT collections at the EROS Data Center, the Scripps Institute of Oceanography, and NOAA. These data provide a current and complete picture of polar land and sea ice for studies of sea ice motion and concentration, ice surface temperature, ice shelf extent monitoring, and glaciological feature mapping on land ice sheets. Data from the NOAA-11 satellite comprise the majority of the scenes; however, NOAA-10, -12, -14, and -15 data also supplement the data set. Image data come from HRPT stations at Casey, McMurdo, Palmer, Fairbanks, Prince Albert, Tromsø, Tokyo, Polar Star, Sioux Falls, Yakutsk, and from recorded LAC images of both polar regions.
Image files consist of five bands within the visible, near-, middle-, and thermal-infrared spectral regions. Image spatial resolution is 1.1 km along swath centerlines, but degrades to several kilometers at the outer edges of the swaths. The sensor channel gains have 10-bit (0-1023) sensitivity and span the range of normal surface and atmospheric radiances in their respective bands.
Temporal coverage begins 1 April 1992 for the Southern Hemisphere, and 1 August 1993 for the Northern Hemisphere. Data continue through present. For areas poleward of 60 degrees north and south latitude, the frequency of spatial coverage ranges from one to several scenes per day; however, gaps exist. Spatial coverage of the entire data set is approximately the same as that enclosed by Special Sensor Microwave/Imager (SSM/I) polar grids, including all polar land ice sheets, sea ice, and high latitude land. This data set covers the following regions of interest:
Refer to ITT 1982 and Hastings and Emery 1992.
The AVHRR sensor is a cross-track scanning system. The NOAA-10 AVHRR has four channels, while the NOAA-9, -11, -12, -14, and -15 AVHRR sensors have five channels each. The instantaneous field of view (IFOV) of each channel is approximately 1.4 milliradians, leading to a satellite subpoint resolution of 1.1 km at a nominal altitude of 833 km. The AVHRR scanning rate is 360 scans per minute, which corresponds to 1.1 km coverage of the satellite ground track. Refer to Reichenbach et. al 1995 for a more detailed explanation of AVHRR pixel size and sampling characteristics. Schowengerdt 1987 provides more information about modulation transfer functions, point-spread function, and pixel sampling.
NSIDC receives Antarctic HRPT data from Scripps Institute of Oceanography via tape, and LP DAAC Global Land 1 km data and NOAA SAA data via ftp.
Observations are not available.
Data are divided into individual scenes. Each scene consists of an image data file with five bands; a header file describing acquisition location, time, and data quality; and a file containing a byte-sum check number to confirm the complete image transfer. A typical scene in level 1b format is 70 MB.
The following maps show coverage of individual scenes (blue) for a single day. The red outline in the Southern Hemisphere image illustrates coverage of a single scene.
Northern Hemisphere
Southern Hemisphere
AVHRR pixel size is 1.1 km at the swath center line (satellite nadir), degrading to 5 km or more at the swath edges (Kidwell 1991). True spatial resolution is slightly coarser than the pixel size for all AVHRR sensors.
Temporal coverage begins 1 April 1992 for the Southern Hemisphere and 1 August 1993 for the Northern Hemisphere. Data continue through present and are available through the AVHRR Archive Browse Tool.
Coverage for most areas is at least once per day. Coverage is several times per day for areas near Tromsø, Fairbanks, McMurdo, and Palmer receiving stations.
Level 1b images represent data from visible, near-, mid-, and thermal-infrared spectra.
Pixel values represent sensor counts or Data Numbers (DNs) that range from 0 to 1023 for each band.
NSIDC obtains Global Land 1 km AVHRR data from the LP DAAC, Antarctic HRPT data from the Scripps Institute of Oceanography, DOMSAT data from the University of Colorado through 1998, and SAA data from NOAA after 1998.
Reduced-resolution browse images are available via the NSIDC AVHRR Archive Browse Tool. NSIDC generates browse images for each AVHRR scene to illustrate the area of coverage. A summary of data quality, cloud cover, and initial estimates of albedo and surface temperature accompany each browse image. Browse images are derived from the level 1b data by manipulating raw sensor values for bands 2 (visible) and 4 (near-infrared) using Land Analysis System (LAS) software from the LP DAAC. The procedure selects every fourth pixel in every fourth line from bands 2 and 4, and divides the raw sensor value of those pixels by four. The single-band components of the browse images are 512 pixels wide and vary in length between approximately 300 and 1300 lines. Dividing the raw 10-bit sensor values by four creates an 8-bit per pixel browse scene. Coastlines, major political boundaries, and major rivers are overlain on the browse images with a data value of 255 for the band 2 browse images and 0 for the band 4 browse images. NSIDC combines the band 2 and 4 images into a seamless 1024-pixel browse image using Interactive Display Language (IDL).
A browse image in Hierarchical Data Format (HDF) also accompanies each level 1b file. The National Center for Supercomputing Applications (NCSA) developed HDF. Tools to extract and display HDF images are available from the NCSA Web site.
Data are stored in NOAA level 1b orbital swath format. A level 1b file contains a one-line header followed by a series of records (one for each line of the image) with navigation, calibration, time of acquisition, and other information at the beginning of each record. The records contain band-interleaved-by-pixel (BIP) image data in a "packed" format with three right-justified 10-bit radiometric measurements packed into four bytes (30 bits stored in 32 bits or four bytes). For more information, refer to the Dundee Satellite Receiving Station's NOAA Level 1B File Format Web page or the online NOAA Polar Orbiter Data User's Guide.
File Naming Convention:
The following illustrates the file naming convention for AVHRR level 1b files:
ppp_sss_YYMMDD_HHMM.l1b
where:
ppp = satellite platform
a10 = NOAA-10
a11 = NOAA-11
a12 = NOAA-12
a14 = NOAA-14
a15 = NOAA-15
sss = receiving station
csy = Casey Station, Antarctica
hbt = Hobart, Australia
lcn = LAC data, Northern Hemisphere
lcs = LAC data, Southern Hemisphere
mcm = McMurdo Station, Antarctica
ngc = Fairbanks, AK
pal = Palmer Station, Antarctica
pas = Prince Albert, Canada
tkz = Tokyo, Japan
s1n = Polar Star (U.S. Coast Guard cutter)
sfl = Sioux Falls, South Dakota, USA
tms = Tromsø, Norway
ykt = Yakutsk, Siberia, Russia
YYMMDD = date of acquisition (year, month, day)
HHMM = start time in Greenwich Mean Time (GMT)
The file naming convention is the same for the header and browse files that accompany the level 1b files, except that the file extension is .ahdr or .brws, respectively.
On-board calibration information is included in the data stream, but it is not applied to the data. Level 1b AVHRR data are neither calibrated nor geolocated (Vermote and Kaufman 1995).
Sensor noise is less of an error factor than quantization error (Schowengerdt 1987). Calibration drift for sensors is also a known error source (Vermote and Kaufman 1995).
Limitations, known problems, and usage guidance are not available.
The AVHRR sensor is characterized by high sensitivity in all channels. The AVHRR Polar 1km Level 1b Data Set provides consistent temporal coverage at a resolution useful for many processes and mapping studies. Following is a list of potential applications:
NSIDC plans to continue acquiring level 1b data over both poles through the end of 2001.
Di, L. and D. Rundquist. 1994. A one-step algorithm for correction and calibration of AVHRR level 1B data. Photogrammetric Engineering & Remote Sensing 60(2):165-171.
Hastings, D. and W. Emery. 1992. The Advanced Very High Resolution Radiometer (AVHRR): a brief reference guide. Photogrammetric Engineering & Remote Sensing 58(8):1183-1188.
ITT. 1982. AVHRR/2 Advanced Very High Resolution Radiometer Technical Description. Prepared by ITT Aerospace/Optical Division. Ft. Wayne, Indiana for NASA Goddard Space Flight Center, Greenbelt, MD 20771, under NASA Contract No. NAS5-26771.
Kidwell, K. 1991. NOAA polar orbiter data user's guide. NOAA/NESDIS/NCDC/SDSD, Washington, D.C.
National Oceanic and Atmospheric Administration (NOAA). 1979. Data extraction and calibration of Tiros-N/NOAA radiometers. Editor, Walter G. Planet. NOAA Technical Memorandum NESS 107 -- Rev. 1. U.S. Dept. of Commerce.
Reichenbach, S., D. Koehler, and D. Strelow. 1995. Restoration and reconstruction of AVHRR images. IEEE Transactions on Geoscience and Remote Sensing 33(4):997-1007.
Schowengerdt, R. 1987. Modify University of Arizona Restoration, Software Module System, AVHRR Image Deconvolution/Resampling Capability. Final Report to USGS Contract No. PO 060206-86, 45 pp.
Steffen, K., R. Bindschadler, G. Casassa, J. Comiso, D. Eppler, F. Fetterer, J. Hawkins, J. Key, D. Rothrock, R. Thomas, R. Weaver, and R. Welch. 1993. Snow and ice applications of AVHRR in polar regions: report of a workshop held in Boulder, Colorado, 20 May 1992. Annals of Glaciology 17:1-15.
Vermote, E. and Y. Kaufman. 1995. Absolute calibration of AVHRR visible and near-infrared channels using ocean and land views. International Journal of Remote Sensing 16(13):2317-2340.
"Navigate" software, created by Dan Baldwin of the Colorado Center for Astrodynamics Research (CCAR), geolocates AVHRR level 1b data. This software is available via anonymous ftp from CCAR. Users should download the following files:
Other software that read and display AVHRR level 1b data include:
NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449 USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
e-mail: nsidc@nsidc.org
Users can select images of interest from the AVHRR Archive Browse Tool. NSIDC writes the corresponding level 1b data to 8-mm tape. Contact NSIDC User Services for more information.
AVHRR: Advanced Very High Resolution Radiometer
BIP: Band-Interleaved-By-Pixel
CCAR: Colorado Center for Astrodynamics Research
DEC: Digital Equipment Corporation
DN: Data Number
DOMSAT: Domestic Satellite
GAC: Global Area Coverage
IFOV: Instantaneous Field of View
HRPT: High Resolution Picture Transmission
LAC: Local Area Coverage
LAS: Land Analysis System
LP: Land Processes
MODIS: Moderate-Resolution Imaging Spectroradiometer
NOAA: National Oceanic and Atmospheric Administration
NSIDC: National Snow and Ice Data Center
SSM/I: Special Sensor Microwave/Imager
Revision Date: 02 August 2001
Review Date: 22 February 1995
Document ID: NSIDC-0022
To broaden awareness of our services, NSIDC requests that you acknowledge the use of data sets distributed by NSIDC. Please refer to the citation below for the suggested form, or contact NSIDC User Services for further information. We also request that you send us one reprint of any publication that cites the use of data received from our Center. This helps us to determine the level of use of the data we distribute. Thank you.
Scambos, T. 1995. AVHRR polar 1 km level 1b data set. Boulder, CO, USA: National Snow and Ice Data Center. Digital Media.
Document Curators: NSIDC Writers
Document URL: http://nsidc.org/data/docs/daac/nsidc0022_avhrr_l1b.gd.html
