NASA/TMm2000-209891, Vol. 102

Technical Report Series on the

Boreal Ecosystem-Atmosphere Study (BOREAS)

Forrest G. Hall, Editor

Volume 102

BOREAS Level-4b AVHRR-LAC Ten-Day

Composite Images: At-sensor Radiance

Josef Cihlar and Jing Chen, Canada Centre for Remote Sensing, Ottawa, Ontario, Canada

Jaime Nickeson and Jeffrey A. Newcomer, Raytheon ITSS, NASA Goddard Space Flight Center,

Greenbelt, Maryland

Fengting Huang, Canada Centre for Remote Sensing, Ottawa, Ontario, Canada

National Aeronautics and

Space Administration

Goddard Space Flight Center

Greenbelt, Maryland 20771

September 2000

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NASA/TMm2000-209891, Vol. 102

Technical Report Series on the

Boreal Ecosystem-Atmosphere Study (BOREAS)

Forrest G. Hall, Editor

Volume 102

BOREAS Level-4b AVHRR-LAC Ten-Day

Composite Images: At-sensor Radiance

Josef Cihlar and Jing Chen, Canada Centre for Remote Sensing, Ottawa, Ontario, Canada

Jaime Nickeson and Jeffrey A. Newcomer, Raytheon ITSS, NASA Goddard Space Flight Center,

Greenbelt, Maryland

Fengting Huang, Canada Centre for Remote Sensing, Ottawa, Ontario, Canada

National Aeronautics and

Space Administration

Goddard Space Flight Center

Greenbelt, Maryland 20771

September 2000
NASA Center for AeroSpace Information

7121 Standard Drive

Hanover, MD 21076-1320

Price Code: A17

Available from:

National Technical Information Service

5285 Port Royal Road

Springfield, VA 22161

Price Code: A10
BOREAS Level-4b AVHRR-LAC Ten-Day Composite Images: At-sensor

Radiance

Josef Cihlar, Jing Chen, Jaime Nickeson, Jeffrey A. Newcomer, Fengting Huang

Summary

The BOREAS Staff Science Satellite Data Acquisition Program focused on providing the research

teams with the remotely sensed satellite data products they needed to compare and spatially extend

point results. MRSC and BORIS personnel acquired, processed, and archived data from the AVHRR

instruments on the NOAA-11 and -14 satellites. The AVHRR data were acquired by CCRS and were

provided to BORIS for use by BOREAS researchers. These AVHRR level-4b data are gridded, 10-day

composites of at-sensor radiance values produced from sets of single-day images. Temporally, the

10-day compositing periods begin 11-Apr-1994 and end 10-Sep-1994. Spatially, the data cover the

entire BOREAS region. The data are stored in binary image format files.

Note that some of the data files on the BOREAS CD-ROMs have been compressed using the Gzip

program. See Section 8.2 for details.

Table of Contents

1) Data Set Overview

2) Investigator(s)

3) Theory of Measurements

4) Equipment

5) Data Acquisition Methods

6) Observations

7) Data Description

8) Data Organization

9) Data Manipulations

10) Errors

11) Notes

12) Application of the Data Set

13) Future Modifications and Plans

14) Software

15) Data Access

16) Output Products and Availability

17) References

18) Glossary of Terms

19) List of Acronyms

20) Document Information

1. Data Set Overview

1.1 Data Set Identification

BOREAS Level-4b AVHRR-LAC Ten-Day Composite Images: At-sensor Radiance

1.2 Data Set Introduction

The BOReal Ecosystem-Atmosphere Study (BOREAS) Staff Science effort covered those activities

that were BOREAS community-level activities or required uniform data collection procedures across

sites and time. These activities included the acquisition of the relevant satellite data. Data from the

Advanced Very High Resolution Radiometer (AVHRR) instrument on the National Oceanic and

Atmospheric Association (NOAA)-9, -11, -12, and -14 satellites were acquired by the Canada Centre

for Remote Sensing (CCRS) and were provided for use by BOREAS researchers.

Page 1
1.3 Objective/Purpose

ForBOREAS,thelevel-4b10-daycompositeAVHRR-LocalAreaCoverage(LAC) imagery,

alongwith theotherremotelysensedimages,wascollectedin ordertoprovidespatiallyextensive

informationovertheprimarystudyareasatvaryingspatialscales.Thisinformationincludesdetailed

landcoverandbiophysicalparametermapssuchasFractionof PhotosyntheticallyActiveRadiation

(FPAR)andLeafAreaIndex(LAI). TheManitobaRemoteSensingCenter(MRSC)andCCRS

processedthelevel-4b10-daycompositeAVHRR-LAC imageryproducts.

1.4 Summary of Parameters

The level-4b 10-day composite AVHRR-LAC data in the BOREAS Information System (BORIS)

contains the following parameters: image header and compositing information; geographic position

information; scaled at-sensor radiance values for image bands 1 to 5; Normalized Difference Vegetation

Index (NDVI); view and solar angle information.

1.5 Discussion

Level-4b data sets are subsets of 10-day composite images produced by Geocoding and

Compositing (GEOCOMP) for the Northern Biosphere Observation and Modeling Experiment

(NBIOME) (Cihlar, 1993). While the NBIOME composite covers all of Canada, a bounding rectangle

encompassing the BOREAS region has been extracted for the level-4b product.

The level-4b processing starts with single-day raw data. Each image is registered to a map

projection (Lambert Conformal Conic [LCC]), resampled, and incorporated into a 10-day composite

using the maximum NDVI compositing criterion (e.g., each pixel is retained only if its NDVI is greater

than that of the pixel already in the composite; in this manner, the composite contains fewer and fewer

contaminated pixels on successive days). Once a pixel is retained, the three angles describing the

acquisition geometry and the acquisition date are also saved in separate files.

The level-4b product contains the data exactly as produced by GEOCOMP. Because GEOCOMP

processes the data in near-real time, the knowledge of AVHRR calibration is not always the best. In

some cases, the calibration becomes known more accurately later (e.g., for NOAA-14 AVHRR). Such

knowledge was not incorporated in the level-4b (or level-3b) products but was used to produce

level-4c products.

1.6 Related Data Sets

BOREAS Level-3b AVHRR-LAC Imagery: Scaled At-sensor Radiance in LGSOWG Format

BOREAS Level-4c AVHRR-LAC Ten-Day Composite Images: Surface Parameters

2. Investigator(s)

2.1 Investigator(s) Name and Title

Josef Cihlar

Canada Centre for Remote Sensing

2.2 Title of Investigation

BOREAS Staff Science Satellite Data Acquisition Program

Page 2
2.3 Contact Information

Contact 1:

Josef Cihlar

Canada Centre for Remote Sensing

588 Booth Street, 4th Floor

Ottawa, Ontario

K1AOY7 Canada

(613) 947-1265

(613) 947-1406 (fax)

Josef.Cihlar@geocan.emr.ca

Contact 2:

Jaime Nickeson

Raytheon ITSS

NASA GSFC

Code 923

Greenbelt, MD 20771

(301) 286-3373

(301) 286-0239 (fax)

Jaime.Nickeson@ gsfc.nasa.gov

3. Theory of Measurements

The AVHRR is a four- or five-channel scanning radiometer capable of providing global daytime and

nighttime information about ice, snow, vegetation, clouds, and the sea surface. These data are obtained

on a daily basis primarily for use in weather analysis and forecasting; however, a variety of other

applications are possible. The AVHRR data collected for the BOREAS project were from instruments

onboard NOAA-9, -11, and -12 polar orbiting platforms. The radiometers measured emitted and

reflected radiation in the visible, near-infrared, middle-infrared, and one or two thermal channels.

The primary use of each channel and spectral regions and band widths on the respective NOAA

platforms are given in the following tables:

Channel Wavelength [_m] Primary Use

i* 0.57 - 0.69 Daytime Cloud and Surface Mapping

2 0.72 - 0.98 Surface Water Delineation, Vegetation Cover

3 3.52 - 3.95 Sea Surface Temperature (SST), Nighttime

Cloud Mapping

4** 10.3 - 11.40 Surface Temperature, Day/Night Cloud Mapping

5*** 11.4 - 12.40 Surface Temperature

* Channel 1 wavelength for the Television and Infrared Observation Satellite

(TIROS)-N flight model was 0.55-0.90 _m.

** For NOAA-7 and -9, channel 4 was 10.3-11.3 _m.

*** For TIROS-N and NOAA-6, -8, -i0, and 12, channel 5 duplicates channel 4.

The wavelength ranges at 50 percent relative spectral response (in micrometers) of the bands for the

platform-specific instruments are:

Page 3
Band NOAA-9 NOAA-II NOAA-12 NOAA-14

1 0.570 - 0.699 0.572 - 0.698 0.571 - 0.684 0.570 - 0.699

2 0.714 - 0.983 0.716 - 0.985 0.724 - 0.984 0.714 - 0.983

3 3.525 - 3.931 3.536 - 3.935 3.554 - 3.950 3.525 - 3.931

4 10.334 - 11.252 10.338 - 11.287 10.601 - 11.445 10.330 - 11.250

5 11.395 - 12.342 11.408 - 12.386 10.601 - 11.445 11.390 - 12.340

The AVHRR can operate in both real-time and recorded modes. Direct readout data were transmitted to

ground stations of the automatic picture transmission (APT) class at low resolution (4 x 4 km) and to

ground stations of the high-resolution picture transmission (HRPT) class at high resolution (1 x 1 km).

AVHRR HRPT data were received for the BOREAS region by the CCRS Prince Albert Satellite

Station (PASS).

4. Equipment

4.1 Sensor/Instrument Description

The AVHRR is a cross-track scanning system featuring one visible, one near-infrared, one

middle-infrared, and two thermal channels. The analog data output from the sensors is digitized

onboard the satellite at a rate of 39,936 samples per second per channel. Each sample step corresponds

to an angle of scanner rotation of 0.95 milliradians. At this sampling rate, there are 1.362 samples per

instantaneous field of view (IFOV). A total of 2,048 samples is obtained per channel per Earth scan,

which spans an angle of +/-55.4 degrees from nadir.

4.1.1 Collection Environment

The NOAA satellites orbit Earth at an altitude of 833 kin. From this space platform, the data are

transmitted to a ground receiving station.

4.1.2 Source/Platform

Launch and available dates for the TIROS-N series of satellites from CCRS are:

Satellite Launch Date Date Range

TIROS-N 13-Oct-1978 19-Oct-1978 to 30-Jan-1980

NOAA-6 27-Jun-1979 21-Aug-1984 to 23-Jan-1986

NOAA-B 29-May-1980 Failed to achieve orbit

NOAA-7 23-Jun-1981 24-Jui-1983 to 30-Dec-1984

NOAA-8 28-Mar-1983 24-Jui-1983 to 13-Aug-1985

NOAA-9 12-Dec-1984 16-Sep-1985 to 19-Mar-1995

NOAA-10 17-Sep-1986 ii-Oct-1986 to 15-Nov-1993

NOAA-II 24-Sep-1988 28-Jun-1989 to 13-Sep-1994

NOAA-12 14-May-1991 ll-Aug-1993 to present

NOAA-14 30-Dec-1994 15-May-1995 to present

AVHRR-LAC data used in BOREAS were collected onboard the NOAA-9, -11, and -12 polar orbiting

platforms. Only NOAA-11 and -14 data were processed as level-4b products.

4.1.3 Source/Platform Mission Objectives

The AVHRR is designed for multispectral analysis of meteorologic, oceanographic, and

hydrologic parameters. The objective of the instrument is to provide radiance data for investigation of

clouds, land-water boundaries, snow and ice extent, ice or snow melt inception, day and night cloud

distribution, temperatures of radiating surfaces, and SST. It is an integral member of the payload on

the advanced TIROS-N spacecraft and its successors in the NOAA series, and as such contributes data

required to meet a number of operational and research-oriented meteorological objectives.

Page 4
4.1.4 Key Variables

Emitted radiation, reflected radiation.

4.1.5 Principles of Operation

The AVHRR is a four- or five-channel scanning radiometer that detects reflected and emitted

radiation from Earth in the visible, near-, mid-, and thermal-infrared regions of the spectrum. A fifth

channel was added to the follow-on instrument designated AVHRR/2 and flown on NOAA-7, -9, - 11,

and -14 to improve the correction for atmospheric water vapor. Scanning is provided by an elliptical

beryllium mirror rotating at 360 rpm about an axis parallel to that of Earth. A two-stage radiant cooler

is used to maintain a constant temperature of 95 K for the infrared detectors. The operating temperature

is selectable at either 105 or 110 K. The telescope is an 8-inch afocal, all-reflective Cassegrain system.

Polarization is less than 10 percent. Instrument operation is controlled by 26 commands and monitored

by 20 analog housekeeping parameters.

4.1.6 Sensor/Instrument Measurement Geometry

The AVHRR is a cross-track scanning system. The IFOV of each sensor is approximately 1.4

milliradians, giving a spatial resolution of 1.1 km at the satellite subpoint. There is about a 36-percent

overlap between IFOVs (1.362 samples per IFOV). The scanning rate of the AVHRR is six scans per

second, and each scan spans an angle of +/-55.4 degrees from the nadir.

4.1.7 Manufacturer of Sensor/Instrument

ITT Aerospace

P.O. Box 3700

Fort Wayne, IN 46801-3700

4.2 Calibration

The thermal-infrared channels are calibrated in-flight using a view of a stable blackbody and space

as a reference. No in-flight reflective channel calibration is performed. Channel 3 data are noisy

because of a spacecraft problem and may not be usable, especially when the satellite is in daylight

(Kidwell, 1991).

4.2.1 Specifications

IFOV 1.4 mRad

RESOLUTION i.i km

ALTITUDE 833 km

SCAN RATE 360 scans/min

SCAN RANGE -55.4 to 55.4

SAMPLES/SCAN 2,048 samples

(1.362 samples per IFOV)

degrees

per channel per Earth scan

4.2.1.1 Tolerance

The AVHRR infrared channels 3-5 were designed for a Noise Equivalent Differential Temperature

(NEdT) of 0.12 K (at 300 K), and a signal-to-noise ratio of 3:1 at 0.5 percent albedo.

4.2.2 Frequency of Calibration

The Naval Research Laboratory's (NRL's) TIROS-N calibration overlay performs the calibration

on blocks of telemetry data. For LAC/HRPT acquisitions, a block consists of 20 scan lines.

Calibration begins by reading the calibration parameters into memory. For each scan line of telemetry

in a block, the following process takes place:

• Telemetry data are extracted and unpacked.

• Ramp calibration data for each of the five channels are decommutated.

• A single Platinum Resistor Thermometer (PRT) count is extracted.

• Ten samples of internal target, or blackbody, data are decommutated and filtered.

• Ten samples of space view data are decommutated and filtered.

Page 5
After theentireblockhasbeendecommutated,thePRTsarecheckedfor patterncorrectness.A valid

PRTpatternconsistsof aPRTreferencecountwhosevalueis lessthan10followedby 4 PRTcounts

whosevaluesaregreaterthan10.After decommutation,thePRTcountsarefiltered,andthemeanand

standarddeviationof eachPRTarecomputed.ThemeanPRTcountsarethenconvertedto temperature

usingtheformula:

T(1) = C(0)+ C(1)M(j) + C(2)[M(j)2]+ C(3)[M(j)3]+ C(4)[M(j)41

where: T(1) = thetemperatureof eachof thefour PRTs

C(i)= thePRTcoefficientsfrom CPIDS

M(j) = themeancountof eachof thefour PRTs

Themeanof thefourPRTtemperaturesis thencomputedto getthetemperatureof theblackbody.The

blackbodytemperatureis usedto calculatetheindexof thetemperature-to-radiancelookuptableusing

theformula:

INDEX = 10.0* PRTTEMPERATURE1798.5

Theblackbodyradiancesforinfraredchannelsareextractedfrom thetable,whichwasgeneratedfrom

CPIDS.Fromthedecommutatedblackbodydata,themeanandstandarddeviationof theinternaltarget

arecomputed.Thiscomputationis alsodonefor themeanandstandarddeviationof spaceview data.

Theslopesandinterceptsarethencalculatedusingthepreviouslycomputeddata.Theslopeand

interceptfor thevisiblechannelsareassignedconstants.Foreachof theinfraredchannels,theslope

andinterceptarecalculatedusingtheformula:

SPACEVIEWRADIANCE- BLACKBODY RADIANCE

SLOPE......................................................................

SPACEVIEWMEAN - BLACKBODY MEAN

INTERCEPT= SPACEVIEWRADIANCESLOPE* SPACEVIEWMEAN

Theslopesandinterceptsfor all five channelsarethenstoredin eachscanline in thegivenblock.The

calibrationoverlaythenbeginsthisprocessagainforthenextblock.Thefinal functionof the

calibrationoverlayis to determineramplinearityornonlinearity.Thisprocessreversestherampon

infraredchannelsfrom descendingto ascending.Therampvaluesarethenadjustedaccordingto data

type(i.e.,LAC or GlobalAreaCoverage(GAC)).

4.2.3 Other Calibration Information

None given.

5. Data Acquisition Methods

The BOREAS level-4b AVHRR-LAC images were provided by the CCRS. Some radiometric

corrections along with geometric corrections, are applied to produce the imagery in a spatially corrected

form (LCC projection). A full level-4b AVHRR-LAC image contains approximately 1,200 pixels in

each of approximately 1,200 lines. Before geometric corrections, the ground resolution ranges from

1.1 km at nadir to 2.5 km x 6.8 km at the scanning extremes of 55.4 degrees. The pixel values of the

images are stored in 2-byte fields. The level-4b images were processed through the CCRS GEOCOMP

system, which applies both radiometric and spatial corrections to the images. Only the raw data are

available from the CCRS PASS.

Page 6
6.1 Data Notes

None.

6.2 Field Notes

None.

6. Observations

7. Data Description

7.1 Spatial Characteristics

7.1.1 Spatial Coverage

The AVHRR provides for a global (pole to pole) onboard collection of data from all spectral

channels. The 110.8-degree scan equates to a swath of 27.2 degrees in longitude (at the Equator)

centered on the subsatellite track. This swath width is greater than the 25.3-degree separation between

successive orbital tracks and provides overlapping coverage (sidelap) anywhere on the globe.

The BOREAS level-4b AVHRR-LAC images contain 1,200 pixels in each of the 1,200 lines and

cover the entire 1,000-kin x 1,000-kin BOREAS region. This includes the Northern Study Area

(NSA), the Southern Study Area (SSA) and the transect between the SSA and NSA.

The North American Datum of 1983 (NAD83) comer coordinates of the AVHRR images are:

Latitude Longitude

Northwest (i,i) 59.36395°N I15.40859°W

Northeast (1,1200) 61.01294°N 93.28553°W

Southwest (1200,1) 48.83387°N II0.25229°W

Southeast (1200,1200) 50.02993°N 93.73857°W

The northwest comer has a distance (1109.76 km west, 7900.04 km north) from the origin (95°W and

0°N) of the LCC coordinate. The pixel size is exactly 1 kin.

The NAD83 corner coordinates of the BOREAS region are:

Latitude Longitude

Northwest 59.979°N III.000°W

Northeast 58.844°N 93.502°W

Southwest 51.000°N III.000°W

Southeast 50.089°N 96.970°W

The NAD83 corner coordinates of the SSA are:

Latitude Longitude

Northwest 54.319°N I06.227°W

Northeast 54.223°N I04.236°W

Southwest 53.513°N I06.320°W

Southeast 53.419°N I04.368°W

Page 7
The NAD83 corner coordinates of the NSA are:

Latitude Longitude

Northwest 56.249°N 98.824°W

Northeast 56.083°N 97.241°W

Southwest 55.542°N 99.045°W

Southeast 55.379°N 97.489°W

7.1.2 Spatial Coverage Map

Not available.

7.1.3 Spatial Resolution

Before any geometric corrections, the spatial resolution varies from 1.1 km at nadir to

approximately 2.5 km x 6.8 km at the extreme edges of the scan. The level-4b composite

AVHRR-LAC images have had geometric corrections applied so that the size for all pixels is 1 km in

all bands.

7.1.4 Projection

The coordinate system is the LCC, with the two standard parallels at 49°N and 77°N, respectively,

and the meridian at 95°W.

7.1.5 Grid Description

The BOREAS level-4b composite images are projected into the LCC projection at a spacing of 1.0

km per pixel (grid cell) in both the X and Y directions.

7.2 Temporal Characteristics

7.2.1 Temporal Coverage

Historical AVHRR-LAC data have been acquired by CCRS routinely since 1991 and are kept in

the CCRS archive. These data can be obtained by contacting CCRS. Statistics Canada also has a

historical composite data set of visible, infrared, and NDVI imagery. Contact the Statistics Canada

Crop Condition Assessment Program office for more information.

At BOREAS latitudes, at least daily coverage is provided by a given sensor. Virtually all raw data

from daytime overpasses were recorded during the BOREAS period (NOAA-11 daytime) and are

archived at PASS. The seasonal time period of data acquisition for the level-4b product is nominally

11-Apr through 31-Oct. In 1994, the period was from 11-Apr through 10-Sept. BORIS contains

relatively complete AVHRR-LAC coverage from NOAA- 11 of central Canada during the snow-free

periods in 1993 and 1994.

7.2.2 Temporal Coverage Map

The 1994 compositing periods in this data set are as follows:

April ii - 20, 21

May 1 - i0, ii - 20, 21

June 1 - i0, ii - 20, 21

July 1 - i0, ii - 20, 21

August 1 - i0, ii - 20, 21

September 1 - i0

- 30

- 31

- 30

- 31

- 30

7.2.3 Temporal Resolution

AVHRR-LAC data processed as level-4b composite products are daytime images (afternoon passes).

Most useful daily images (those containing some clear-sky regions) are used to produce the level-4b

product. The daily images are composited into nominally cloud-free images over 10-day periods.

Page 8
7.3 Data Characteristics

7.3.1 Parameter/Variable

The parameters contained in each image product are:

Scaled At-sensor Radiance

NDVI

View Zenith Angle

Solar Zenith Angle

Relative Azimuth Angle

Date of Acquisition

7.3.2 Variable Description/Definition

At-sensor radiance is the radiant energy measured by the sensor from its position relative to the

target. In this case, it is derived from the signal recorded by the AVHRR sensor, which is then

calibrated by the processes described in Section 9 of this document. The following equations were

used to calculate the radiance in a given band from the counts given:

R(1) = (625/I023)*DN(I) - 25.0

R(2) = (415/I023)*DN(2) - 15.0

R(3) = -(1.508988/I023)*DN(3) + 1.504

R(4) = -(175.898/I023)*DN(4) + 170.8

R(5) = -(183.863/I023)*DN(5) + 179.1

where R(i) is the resulting radiance for band (i), and

DN(i) is the count from band (i) in the digital image.

NDVI is the ratio of the difference between the near-infrared band and the visible band and the sum of

the two bands [(NIR - VIS) / VIS + NIR)].

The values of the imagery have been scaled such that:

NDVI = (DN/10,000) - 1.0

View zenith angle is the position of the sensor relative to the nadir (subsatellite point), with 90 degrees

indicating the horizontal position and 0 degrees being directly overhead. To calculate view zenith:

View Zenith = DN/100

Solar zenith angle is the position of the Sun relative to the horizon, with 90 degrees indicating the

horizontal position and 0 degrees being directly overhead. To calculate solar zenith:

Solar Zenith = DN/X00

Relative azimuth is equal to the solar azimuth minus the sensor view azimuth. Azimuth angles are

measured from North (0 or 360 degrees) and increase clockwise to 90 degrees for east, 180 degrees

for south, etc. To calculate

relative azimuth:

Relative Azimuth = DN/X00

Date of acquisition is the day of year on which that particular pixel in the level-4b composite product

was acquired.

7.3.3 Unit of Measurement

At-sensor radiance units are W/(m2 sr pm) for channels 1 and 2, and mW/(m2 sr cm) for AVHRR

channels 3, 4, and 5.

Page 9
NDVI is unitless.

View zenith is measured in degrees.

Solar zenith is measured in degrees.

Relative azimuth is measured in degrees.

Date of acquisition units are days.

7.3.4 Data Source

The image data were acquired by CCRS and processed by the MRSC in Winnipeg, Manitoba.

7.3.5 Data Range

At-sensor radiance can range from:

AVHRR Band Units DN=0 DN=I023

1 Radiance -25 600

2 Radiance -15 400

3 Radiance 1.504 -0.004988

4 Radiance 170.8 -5.098

5 Radiance 179.1 -4.763

The values of the scaled NDVI imagery range from a DN of 0 to a DN of 20,000.

The scaled values in the view zenith image range from 0 to 9,000.

The scaled values of solar zenith DN range from 0 to 9,000.

The scaled values of relative azimuth range from 0 to 18,000.

Based on a start date of 01-Jan-1970, the relative date of acquisition ranges from 8866

(11-Apr-1994) to 9018 (10-Sep-1994).

7.4 Sample Data Record

Sample data records are not applicable to image data.

8. Data Organization

8.1 Data Granularity

The smallest unit of data for the level-4b AVHRR-LAC composite is the set of parameters for a

given compositing period.

8.2 Data Format(s)

8.2.1 Uncompressed Data Files

A single level-4b AVHRR-LAC composite image product produced by CCRS contains the

following 10 files:

File 1 -- Channel 1 radiance

File 2 -- Channel 2 radiance

File 3 -- Channel 3 radiance

File 4 -- Channel 4 radiance

File 5 -- Channel 5 radiance

File 6 -- NDVI

File 7 -- View zenith angle

File 8 -- Solar zenith angle

File 9 -- Relative azimuth angle

File 10 -- Date of acquisition

Page 10
Theimagescontain1,200pixelsin eachof 1,200lines.Eachpixel valueis containedin a2-byte

(16-bit)field orderedasmostsignificant(high-order)bytefirst.Thus,eachimageline (file record)

contains2,400bytesof data.

Theimagesareorientedsuchthatpixel 1,line 1is in theupperleft-handcomer(i.e.,northwest)of

thescreendisplay.Pixelsandlinesprogressfrom left to right andtopto bottomsothatpixel n, linen

is in thelowerright-handcomer.

8.2.2 Compressed CD-ROM Files

On the BOREAS CD-ROMs, the image files have been compressed with the Gzip (GNU zip)

compression program (file_name.gz). These data have been compressed using gzip version 1.2.4 and

the high compression (-9) option (Copyright (C) 1992-1993 Jean-loup Gailly). Gzip uses the

Lempel-Ziv algorithm (Welch, 1994) also used in the zip and PKZIP programs. The compressed files

may be uncompressed using gzip (with the -d option) or gunzip. Gzip is available from many Web

sites (for example, the ftp site prep.ai.mit.edu/pub/gnu/gzip-*.*) for a variety of operating systems in

both executable and source code form. Versions of the decompression software for various systems

are included on the CD-ROMs

9. Data Manipulations

9.1 Formulae

9.1.1 Derivation Techniques and Algorithms

The level-4b composite product uses the level-3 AVHRR-LAC product in LCC projection as input.

Daily level-4b products are combined to select the most cloud-free pixels during the 10-day

compositing period. By definition, this is the pixel with the highest NDVI value. Once a pixel is

selected, it is retained in the composite image, as are the three associated angles, NDVI, and the day of

year in which the pixel was imaged. The components are created for three separate periods within a

month: 1-10, 11-20, and 21-end of month.

The daily data are not corrected for atmospheric effects prior to creating composites. This is done

to avoid selection of pixels with high view zenith angles (Cihlar and Huang, 1994). Only data for view

zenith angles 57 degrees or less were used in the composite (except for 1993, when data were used

from all zenith angles).

It is important to note that level-4b images were composited from level-3b images processed

separately from the level-3b images contained in BORIS. This is because of the differences in

projections Albers Equal-Area Conic (AEAC) vs. LCC. However, the same calibration and processing

sequences were used, except as noted (e.g., difference in 1995 calibrations).

9.2 Data Processing Sequence

9.2.1 Processing Steps

GEOCOMP created the level-4b composite image by:

• Specifying input parameters for generating the composite image (source images, geographic

region, compositing criterion, compositing period)

• Inputting imagery

• Comparing the NDVI of every pixel of the input level-3 image with that of the corresponding

composite pixel

• If appropriate, replacing values of a composite pixel by those in the daily image for all

channels

• Repeating steps 3 and 4 for all daily images during the compositing period

• Outputting imagery

Page 11
BORISstaffprocessedthedataby:

• Developingandusingsoftwareto verify thecontentof andextractneededinformationfrom

theimagefiles,

• Compressingthebinaryfiles forreleaseonCD-ROM.

9.2.2 Processing Changes

None.

9.3 Calculations

9.3.1 Special Corrections/Adjustments

None.

9.3.2 Calculated Variables

See Section 7.

9.4 Graphs and Plots

None.

10. Errors

10.1 Sources of Error

The major source of error is due to two geometric effects, IFOV and image registration. Because

the IFOV size at large view zenith angles varies for adjacent level-4 pixels on different dates, the

composite pixels represent varying areas (in size and location, thus creating overlaps or gaps) on

Earth's surface. This effect can be assessed using the angular information in the level-4 product. The

other geometric effect is caused by pixel misregistration. Although the registration of level-3b images

is typically done with subpixel accuracy (root mean square [rms]<0.8 km for pixels within 45 degrees

of nadir), the accuracy of the composite products accumulates errors from individual images and

suffers from the reduced accuracy for pixels farther from nadir. This effect is difficult to quantify as it

varies both within the composite image and between composite periods.

The level-4b product is not corrected for atmospheric or bidirectional effects; thus, the composites

have numerous radiometric artifacts caused by these phenomena. The level-4b product also suffers

from errors in the level-3b product (see level-3b product documentation).

10.2 Quality Assessment

10.2.1 Data Validation by Source

Not available.

10.2.2 Confidence Level/Accuracy Judgment

Refer to the level-3b product specification.

10.2.3 Measurement Error for Parameters

None.

10.2.4 Additional Quality Assessments

Composites are assessed visually.

10.2.5 Data Verification by Data Center

BORIS personnel extracted header information, inventoried the AVHRR data acquisition

information in the data base, and viewed some of the imagery to confirm the use of scaling information

provided in Section 7.3.2. Lastly, BORIS staff compressed the image data files for distribution on

CD-ROM.

Page 12
11. Notes

11.1 Limitations of the Data

None.

11.2 Known Problems with the Data

None.

11.3 Usage Guidance

Before uncompressing the Gzip files on CD-ROM, be sure that you have enough disk space to

hold the uncompressed data files. Then use the appropriate decompression program provided on the

CD-ROM for your specific system.

11.4 Other Relevant Information

None.

None given.

12. Application of the Data Set

None.

13. Future Modifications and Plans

14. Software

14.1 Software Description

The GEOCOMP software is written in Pascal and FORTRAN and runs on Digital's VAX

computers. Special code also exists for the GEOCOMP array processor. The GEOCOMP software is

proprietary. Gzip (GNU zip) uses the Lempel-Ziv algorithm (Welch, 1994) used in the zip and PKZIP

commands.

14.2 Software Access

Most of the GEOCOMP software is proprietary. For further information, contact:

MacDonald Dettwiler and Associates

13800 Commerce Parkway

Richmond, BC VGV2J3

(604) 278-3411

Gzip is available from many Web sites across the Intemet (for example, ftp site

prep.ai.mit.edu/pub/gnu/gzip-*.*) for a variety of operating systems in both executable and source

code form. Versions of the decompression software for various systems are included on the

CD-ROMs.

Page 13
15. Data Access

The level-4b AVHRR-LAC 10-day composite images are available from the Earth Observing System

Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active

Archive Center (DAAC).

15.1 Contact Information

For BOREAS data and documentation please contact:

ORNL DAAC User Services

Oak Ridge National Laboratory

P.O. Box 2008 MS-6407

Oak Ridge, TN 37831-6407

Phone: (423) 241-3952

Fax: (423) 574-4665

E-mail: ornldaac@ornl.gov or ornl@eos.nasa.gov

15.2 Data Center Identification

Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory

(ORNL) Distributed Active Archive Center (DAAC) for Biogeochemical Dynamics

http://www-eosdis.ornl.gov/.

15.3 Procedures for Obtaining Data

Users may obtain data directly through the ORNL DAAC online search and order system

[http://www-eosdis.ornl.gov/] and the anonymous FTP site [ftp://www-eosdis.ornl.gov/data/] or by

contacting User Services by electronic mail, telephone, fax, letter, or personal visit using the contact

information in Section 15.1.

15.4 Data Center Status/Plans

The ORNL DAAC is the primary source for BOREAS field measurement, image, GIS, and

hardcopy data products. The BOREAS CD-ROM and data referenced or listed in inventories on the

CD-ROM are available from the ORNL DAAC.

16. Output Products and Availability

16.1 Tape Products

The AVHRR-LAC level-4b 10-day composite data can be made available on 8-ram media.

16.2 Film Products

None.

16.3 Other Products

These data are available on the BOREAS CD-ROM series.

Page 14
17. References

17.1 Platform/Sensor/Instrument/Data Processing Documentation

Buffam, A. 1994. GEOCOMP User Manual. Internal Report, Canada Centre for Remote Sensing,

Ottawa, Ontario.

Cihlar, J. and F. Huang. 1993. User guide for the 1993 GEOCOMP products. NBIOME Internal

Report, Canada Centre for Remote Sensing, Ottawa, Ontario. 9 p.

Cihlar, J. and F. Huang. 1994. Effect of atmospheric correction and viewing angle restriction on

AVHRR composites. Canadian Journal for Remote Sensing 20: 132-137.

Hussey, J.W. 1977. The TIROS-N NOAA Operational Satellite System. U.S. Department of

Commerce, NOAA/NESS.

Kidwell, K. 1991. NOAA Polar Orbiter Data User's Guide, NCDC/SDSD. (Updated from original

1984 edition.)

Lauritson, et al. 1979. Data Extraction and Calibration of TIROS N/NOAA Radiometers." NOAA

Technical Memorandum NESS 107, U.S. Department of Commerce, NOAA/NESS.

Welch, T.A. 1984. A Technique for High Performance Data Compression. IEEE Computer, Vol. 17,

No. 6, pp. 8-19.

17.2 Journal Articles and Study Reports

Cihlar, J. and P.M. Teillet. 1995. Forward piecewise linear calibration model for quasi-real time

processing of AVHRR data. Canadian Journal of Remote Sensing 21: 22-27.

Newcomer, J., D. Landis, S. Conrad, S. Curd, K. Huemmrich, D. Knapp, A. Morrell, J. Nickeson,

A. Papagno, D. Rinker, R. Strub, T. Twine, F. Hall, and P. Sellers, eds. 2000. Collected Data of The

Boreal Ecosystem-Atmosphere Study. NASA. CD-ROM.

Robertson, B., A. Erickson, J. Friedel, B. Guindon, T. Fisher, R. Brown, P. Teillet, M. D'Iorio, J.

Cihlar, and A. Sancz. 1992. GEOCOMP, a NOAA AVHRR geocoding and compositing system.

Proceedings of the ISPRS Conference, Commission 2, Washington, DC, 223-228.

Sellers, P. and F. Hall. 1994. Boreal Ecosystem-Atmosphere Study: Experiment Plan. Version

1994-3.0, NASA BOREAS Report (EXPLAN 94).

Sellers, P. and F. Hall. 1996. Boreal Ecosystem-Atmosphere Study: Experiment Plan. Version

1996-2.0, NASA BOREAS Report (EXPLAN 96).

Sellers, P., F. Hall, and K.F. Huemmrich. 1996. Boreal Ecosystem-Atmosphere Study: 1994

Operations. NASA BOREAS Report (OPS DOC 94).

Sellers, P., F. Hall, and K.F. Huemmrich. 1997. Boreal Ecosystem-Atmosphere Study: 1996

Operations. NASA BOREAS Report (OPS DOC 96).

Sellers, P., F. Hall, H. Margolis, B. Kelly, D. Baldocchi, G. den Hartog, J. Cihlar, M.G. Ryan, B.

Goodison, P. Crill, K.J. Ranson, D. Lettenmaier, and D.E. Wickland. 1995. The boreal

ecosystem-atmosphere study (BOREAS): an overview and early results from the 1994 field year.

Bulletin of the American Meteorological Society. 76(9): 1549-1577.

Page 15
Sellers,P.J.,F.G.Hall, R.D.Kelly, A. Black, D. Baldocchi,J. Berry, M. Ryan,K.J. Ranson,P.M.

Crill, D.P.Lettenmaier,H. Margolis,J.Cihlar, J.Newcomer,D. Fitzjarrald,P.G.Jarvis,S.T.

Gower,D. Halliwell, D. Williams, B. Goodison,D.E.Wickland, andF.E.Guertin.1997.BOREAS

in 1997:ExperimentOverview,ScientificResultsandFutureDirections.Journalof Geophysical

Research102(D24):28,731-28,770.

Teillet,P.M.andB.N. Holben.1994.Towardsoperationalradiometriccalibrationof NOAA AVHRR

imageryin thevisibleandnear-infraredchannels.CanadianJournalof RemoteSensing20: 1-10.

Townshend,J.(Ed.).1995.Globaldatasetsfor thelandfrom AVHRR. InternationalJournalof

RemoteSensing15:3315-3639(specialissuedescribingseveralprogram-generatingcomposite

AVHRR imagedatasets).

17.3 Arehive/DBMS Usage Documentation

None.

None.

18. Glossary of Terms

AEAC

APC

ASCII

AVHRR

BOREAS

BORIS

BPI

CCRS

CCT

CD-ROM

CPIDS

DAAC

DAT

DN

EOS

EOSDIS

EROS

FPAR

GAC

GEOCOMP

GIS

GSFC

HRPT

IFC

IFOV

LAC

LAI

LCC

LGSOWG

MRSC

19. List of Acronyms

- Albers Equal-Area Conic

- Automatic Picture Transmission

- American Standard Code for Information Interchange

- Advanced Very High Resolution Radiometer

- BOReal Ecosystem-Atmosphere Study

- BOREAS Information System

- Bytes per inch

- Canada Centre for Remote Sensing

- Computer-Compatible Tape

- Compact Disk-Read-Only Memory

- Calibration Parameter Input Dataset

- Distributed Active Archive Center

- Digital Archive Tape

- Digital Number

- Earth Observing System

- EOS Data and Information System

- Earth Resources Observation System

- Fraction of Photosynthetically Active Radiation

- Global Area Coverage.

- Geocoding and Compositing System

- Geographic Information System

- Goddard Space Flight Center

- High-Resolution Picture Transmission

- Intensive Field Campaign

- Instantaneous Field-of-View

- Local Area Coverage

- Leaf Area Index

- Lambert Conformal Conic

- Landsat Ground Station Operational Working Group

- Manitoba Remote Sensing Centre

Page 16
NAD83

NASA

NBIOME

NDVI

NEdT

NOAA

NRL

NSA

ORNL

PANP

PASS

PRT

RMS

SSA

SST

TIROS

URL

- North American Datum of 1983

- National Aeronautics and Space Administration

- Northern Biosphere Observation and Modeling Experiment

- Normalized Difference Vegetation Index

- Noise Equivalent Differential Temperature

- National Oceanic and Atmospheric Administration

- Naval Research Laboratory

- Northern Study Area

- Oak Ridge National Laboratory

- Prince Albert National Park

- Prince Albert Satellite Station

- Platinum Resistor Thermometer

- Root Mean Square

- Southern Study Area

- Sea Surface Temperature

- Television and Infrared Observation Satellite

- Uniform Resource Locator

20. Document Information

20.1 Document Revision Date

Written: 25-Jul- 1995

Last Updated: 16-Ju1-1999

20.2 Document Review Date(s)

BORIS Review: 11-Sep- 1997

Science Review: 05-Jan- 1998

20.3 Document ID

20.4 Citation

When using these data, please include the following acknowledgment as well as citations of

relevant papers in Section 17.2:

The data were acquired by CCRS and processed by the MRSC in Winnipeg, Manitoba. The

respective contributions of the above individuals and agencies to completing this data set are greatly

appreciated.

If using data from the BOREAS CD-ROM series, also reference the data as:

Cihlar, J. "BOREAS Staff Science Satellite Data Acquisition Program." In Collected Data of The

Boreal Ecosystem-Atmosphere Study. Eds. J. Newcomer, D. Landis, S. Conrad, S. Curd, K.

Huemmrich, D. Knapp, A. Morrell, J. Nickeson, A. Papagno, D. Rinker, R. Strub, T. Twine, F.

Hall, and P. Sellers. CD-ROM. NASA, 2000.

Also, cite the BOREAS CD-ROM set as:

Newcomer, J., D. Landis, S. Conrad, S. Curd, K. Huemmrich, D. Knapp, A. Morrell, J.

Nickeson, A. Papagno, D. Rinker, R. Strub, T. Twine, F. Hall, and P. Sellers, eds. Collected Data of

The Boreal Ecosystem-Atmosphere Study. NASA. CD-ROM. NASA, 2000.

20.5 Document Curator

20.6 Document URL

Page 17
REPORT DOCUMENTATION PAGE FormApproved

OMB No. 0704-0188

Public reporting burden for this collection of informationis estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources,

gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this

collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson

Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188), Washington, DC 20503.

1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED

September 2000 Technical Memorandum

4. TITLE AND SUBTITLE

Technical Report Series on the Boreal Ecosystem-Atmosphere Study (BOREAS)

BOREAS Level-4b AVHRR-LAC Ten-Day Composite hnages: At-sensor

Radiance

6. AUTHOR(S)

Josef Cihlar, Jing Chen, Jaime Nickeson, Jeffrey A. Newcomer,

and Fengting Huang

Forrest G. Hall_ Editor

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS (ES)

Goddard Space Flight Center

Greenbelt, Maryland 20771

9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS (ES)

National Aeronautics and Space Administration

Washington, DC 20546-0001

5. FUNDING NUMBERS

923

RTOP: 923-462-33-01

8. PEFORMING ORGANIZATION

REPORT NUMBER

2000-03136-0

10. SPONSORING / MONITORING

AGENCY REPORT NUMBER

TM--2000-209891

Vol. 102

11. SUPPLEMENTARY NOTES

J. Cihlar, J. Chen, and F. Huang: Canada Centre for Remote Sensing, Ottawa, Ontario, Canada;

J. Nickeson and J.A. Newcomer: Raytheon ITSS, NASA Goddard Space Flight Center,

Greenbel L Maryland

12a. DISTRIBUTION / AVAILABILITY STATEMENT

Unclassifie_Unlimited

Subject Category: 43

Report available from the NASA Center for AeroSpace Information,

7121 Standard Drive, Hanover, MD 21076-1320. (301) 621-0390.

12b. DISTRIBUTION CODE

13. ABSTRACT (Maximum 200 words)

The BOREAS Staff Science Satellite Data Acquisition Program focused on providing the research

teams with the remotely sensed satellite data products they needed to compare and spatially extend

point results. MRSC and BORIS personnel acquired, processed, and archived data from the AVHRR

instruments on the NOAA-11 and -14 satellites. The AVHRR data were acquired by CCRS and were

provided to BORIS for use by BOREAS researchers. These AVHRR level-4b data are gridded, 10-day

composites of at-sensor radiance values produced from sets of single-day images. Temporally, the 10-

day compositing periods begin 11-Apr-1994 and end 10-Sep-1994. Spatially, the data cover the entire

BOREAS region. The data are stored in binary image format files.

14. SUBJECT TERMS

BOREAS, remote sensing science, AVHRR.

17. SECURITY CLASSIFICATION

OF REPORT

Unclassified

NSN 7540-01-280-5500

18. SECURITY CLASSIFICATION

OF THIS PAGE

Unclassified

19. SECURITY CLASSIFICATION

OF ABSTRACT

Unclassified

15. NUMBER OF PAGES

1'7

16. PRICE CODE

20. LIMITATION OF ABSTRACT

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