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GES DISC DAAC Data Guide: CZCS Level 2 GAC

Coastal Zone Color Scanner (CZCS)
4 km Level 1a and Level 2 HDF and DSP Format
Dataset Guide Document

Level 2 Sample Images

4 km resolution images of phytoplankton pigment concentration (a derived geophysical parameter, consisting primarily of chlorophyll and phaeophytin concentration)

Level 1 Sample - Cape Cod Cape Cod

Level 1 Sample - Cape Cod Gibraltar


CZCS was a multi-spectral line scanner devoted principally to measurements of ocean color which operated from November 2, 1978 to June 22, 1986. It had six spectral bands (channels), four of which were devoted to ocean color, each having a 20 nanometer bandwidth and centered at 443, 520, 550, and 670 nanometers. These are referred to as channels 1 through 4, respectively. Channel 5 sensed reflected solar radiance and had a 100 nanometer bandwidth centered at 750 nanometers and a dynamic range which was more suited to land. Channel 6 operated in the 10.5 to 12.5 micrometer region and sensed emitted thermal radiance for derivation of equivalent black body temperature.

This document describes the 4 km resolution (DSP and HDF format) Coastal Zone Color Scanner Level 1a and Level 2 data products archived at the Goddard Space Flight Center (GSFC) Distributed Active Archive Center (DAAC). Other CZCS data products archived at Goddard include 1 km resolution CZCS Level 1 products and 18 km resolution Level 3 composite products. The characteristics of the CZCS Sensor are described in the Coastal Zone Color Scanner Sensor Guide and the Nimbus-7 platform is described in the Nimbus-7 Platform Guide.


Table of Contents


  1. Document Information
  2. Investigator(s)
  3. Dataset Information
  4. Theory of Measurements
  5. Equipment
  6. Procedure
  7. Observations
  8. Data Granularity
  9. Data Description
  10. Data Manipulations
  11. Errors
  12. Notes
  13. Application of the Dataset
  14. Dataset Plans
  15. References
  16. Related Software
  17. Data Access
  18. Output Products and Availability
  19. Glossary of Terms
  20. List of Acronyms

2. Investigators:

Dr. Gene Feldman
Goddard Space Flight Center, Code 610.2.3
Greenbelt, MD20771


Dr. Chuck McClain
McClain - Goddard Space Flight Center, Code 971
Greenbelt, MD20771


Dr. Wayne Esaias
Goddard Space Flight Center, Code 971
Greenbelt, MD20771

Title of Investigation:

Coastal Zone Color Scanner

Contacts (for Data Production Information):

CZCS Data -
Dr. Gene Feldman
Goddard Space Flight Center, Code 610.2.3
Greenbelt, MD20771


Software -
Dr. Bob Evans
University of Miami, RSMAS/MPO
4600 Rickenbacker Causeway
Miami, FL33149

3. Dataset Information


For most regions of the world, the observed color of the ocean is determined primarily by the abundance of phytoplankton and their associated photosynthetic pigments. As the concentration of phytoplankton pigments increases, ocean color shifts from blue to green. The Coastal Zone Color Scanner (CZCS) was a multi-spectral line scanner developed by NASA to measure ocean color as a means of determining photosynthetic pigment concentrations and the distribution of particulate matter and dissolved substances in the oceans.


The purpose of the CZCS on Nimbus-7 was to obtain a global understanding of the temporal and spatial distribution of phytoplankton biomass and primary production, a better understanding of the processes regulating the growth of phytoplankton in the ocean, and increased insight into the processes influencing the ultimate fate of this organically fixed carbon. Satellite observations of ocean color were necessary to provide reliable estimates of marine phytoplankton biomass on synoptic scales which are useful in studies of phytoplankton-related processes. The mission objectives for the CZCS were to obtain observations of ocean color and temperature, particularly in the coastal zones, which would provide data with sufficient spatial and spectral resolution for the following applications:


  • Measure concentrations of chlorophyll-a and phaeophytin.
  • Map biologically productive areas.
  • Map suspended sediment distribution and determine the type of materials suspended in the water.
  • Map Gelbstoff (yellow substances) as an indicator of salinity.
  • Detect pollutants in the upper level of the oceans.
  • Map temperature of coastal waters and the open ocean.
  • Study the interactions between coastal effluents and open waters.


Summary of Level 1 Parameters:

Level 1 data contain at-spacecraft raw radiance counts with calibration and earth location information appended, but not applied. These data contain radiances from the six spectral bands (channels):

	Channel		Wavelength				Purpose
	1		433-453 nm (blue)			Photosynthetic pigment absorption
	2		510-530 nm (green)			Photosynthetic pigment concentration
	3		540-560 nm (yellow)			Gelbstoff concentration
	4		660-680 nm (red)			aerosol absorption
	5		700-800 nm (far red)			land and cloud detection
	6		10.5-12.5 microns (infra-red)		surface temperature


4. Theory of Measurements:

Organic and inorganic particulate matter, as well as some dissolved substances in the water, affect its color. Ocean water containing very little particulate matter scatters as a Rayleigh scatterer, producing the well-known deep purple or bluish color of the open sea. As particulate matter concentrations increase, its light scattering characteristics change and different water colors are observed. Phytoplankton, for instance, have specific absorption characteristics and normally change the water to a more greenish hue--although some phytoplankton, such as various red tide organisms, can change the water to colors such as red, yellow, blue-green or mahogany. Inorganic particulate matter in water, such as the terrigenous outflow from rivers, has a different color from organic material (typically brownish in color but sometimes varying with red). Differentiating between suspended organic and inorganic matter remains a challenge to ocean color scientists today. By sensing the color with very high signal-to-noise ratios in several narrow bands, CZCS provided a mechanism for correlating water color with its contents for the first time.


5. Equipment:

Instrument Description:

CZCS had a scan width of 1556 km centered on nadir and the ground resolution was 0.825 km at nadir. Channels 1-4 were devoted to ocean color, each having 20 nanometer bandwidth and centered at 443, 520, 550, and 670 nm, respectively. Channel 5 sensed reflected solar radiance, but had a 100 nanometer bandwidth centered at 750 nanometers and a dynamic range which was more suited to land. Channel 6 operated in the 10.5 to 12.5 micrometer region and sensed emitted thermal radiance for derivation of equivalent black body temperature.


Collection Environment:

CZCS was launched aboard Nimbus-7 in October 1978. Due to the power demands of the various on-board experiments the CZCS operated on an intermittent schedule. The infra-red/temperature sensor (channel 6 10.5-12.5 microns) failed within the first year. Sometime in 1981 it was determined that the sensitivity of the other CZCS sensors was degrading with time, in particular channel 4. Sensitivity degradation was persistent and increased during the rest of the mission.

In mid-1984, NIMBUS-7 mission personnel experienced turn-on problems with the CZCS system which were related to power supply problems and the annual lower power summer season of NIMBUS-7. Also, spontaneous shutdown of the CZCS system began occurring. These problems also persisted for the rest of the mission. From March 9, 1986 to June 1986, the CZCS system was given highest priority for the collection of a contemporaneous data set of ocean color. It was turned off in June at the start of the low power season with the intention of turning it back on in December when power conditions would be more favorable. Attempts to reactivate CZCS in December 1986 failed. The CZCS sensor was officially declared non-operational on 18 December 1986.

Platform Mission Objectives:

Nimbus-7, launched in October 1978, was a research-and-development satellite serving as a stabilized, earth-observing platform for the testing of advanced systems for sensing and collecting data in the pollution, oceanographic, and meteorological disciplines. It provided an opportunity to assess each instrument's operation in the space environment and to collect a sizable body of data with the global and seasonal coverage needed for support of each experiment. The mission also extended and refined the sounding and atmospheric structure measurement capabilities demonstrated by experiments on previous Nimbus observatories.

Nimbus-7 sensors included a limb infrared monitor of the stratosphere (LIMS), stratospheric and mesopheric sounder (SAMS), coastal-zone color scanner (CZCS), stratospheric aerosol measurement (SAM II), earth radiation budget (ERB), scanning multichannel microwave radiometer (SMMR), solar backscatter UV and total ozone mapping spectrometer (SBUV/TOMS), and temperature-humidity infrared radiometer (THIR). These sensors were capable of observing several parameters at and below the mesospheric levels. After 11 years in orbit, three experiments---SAM II, SBUV/TOMS, and ERB---were still functioning successfully. Nimbus-7 was finally retired in 1995.

Key Variables:

Nominal orbit parameters for the Nimbus-7 spacecraft were:

	Launch date			10/24/78
	Orbit				Sun-synchronous, near polar
	Nominal Altitude (km)		955
	Inclination (deg)		104.9
	Nodal Period (min.)		104
	Equator Crossing Time		1200 noon (ascending)
	Nodal Increment (deg)		26.1

Instrument Measurement Geometry:

CZCS was a cross-track scanning system. The Instantaneous Field of View (IFOV) of each detector was .865 mrad, yielding a resolution of 825 m at the satellite subpoint. The swath covered 1566 km in width from a maximum scan angle of approximately 40 degrees. 1970 samples per scan were collected for channels 1-6.This yielded 94,560 samples per second with an 8 bit (256 level) quantizing resolution. Data were then transmitted to a receiving station at a rate of 800 kbps.


Manufacturer of Instrument:

Ball Aerospace and Technologies Corporation , (



Prelaunch calibration of the CZCS used a 76 cm diameter integrating sphere as a source of diffuse radiance for channels 1 through 5 and a blackbody source for calibration of channel 6. The integrating sphere was especially constructed for calibration of the CZCS and was calibrated from a standard lamp from the National Bureau of Standards utilizing a spectrometer and another integrating sphere to transfer calibration from the lamp to the sphere.

In addition to the sphere and the blackbody, a collimator was used to calibrate the CZCS in vacuum testing. In-flight calibration of the CZCS is accomplished for the first five bands by using a built-in incandescent light source. This in-flight calibration source was calibrated using the instrument itself as a transfer against the referenced sphere output.

Channel 6 was calibrated by viewing the blackened housing of the instrument whose temperature is monitored. Deep space is another calibration viewed during the 360 degree rotation of the scan mirror.

For further details on the CZCS sensor and the Nimbus-7 satellite, please consult The Coastal Zone Color Scanner Instrument Guide ( and the Nimbus 7 Platform Guide (

6. Procedure:


Data Acquisition Methods:

The raw data from the six CZCS channels were either directly transmitted to the ground station in real-time or recorded on the satellite tape recorder for later playback and transmission to the ground station. Data were stored on magnetic tape and sent to the Image Processing Division (IPD) at Goddard Space Flight Center (GSFC). In addition to radiance measurements, these data also include the calibration lamp data and Image Location Data (ILT).

7. Observations:

Data Notes:

(This information is not available for CZCS.)

Field Notes:

(This information is not available for CZCS.)

8.Data Granularity:

Each Level 1a (L1A) or Level 2 (L2) granule is a partial orbital swath with a maximum of 2 minutes of data. One two-minute CZCS scene covers approximately 1.3 million square km of the Earth's surface.

9.Data Description:

Spatial Characteristics:

Spatial Coverage:

Spatial Coverage is global with an emphasis on coastal regions. Spatial coverage varied widely and was very irregular. The plot below shows a composite of the spatial coverage for the entire CZCS mission. Nine additional plots show the geographic distribution of CZCS data for each of the nine years from 1978-1986. Each dot on these plots represents the center point of one CZCS scene. These images show the irregular spatial distribution of the CZCS data set graphically.


Spatial Resolution:

L1A and L2 CZCS scenes had a spatial resolution at nadir of 4 km in each of the six co-registered channels, or in the derived geophysical products.



Level 1a and Level 2 scenes have satellite swath projection.

Temporal Characteristics:

Temporal Coverage:

The archive of CZCS data products began on November 2, 1978 and continued until June 22, l986. However, there are several periods of intermittent coverage. When operating full time, approximately 400 images were collected each month. The following figure shows a graphical display of the temporal distribution of the CZCS L1A and L2 data set.


Temporal Resolution:

Each CZCS scan viewed the Earth for approximately 27.5 microseconds. During this period, each channel of the analog data output was digitized to obtain a total of about 2000 samples. Successive scans occurred at the rate of 8 per second. Subsequent coverage of the same geographic area varied greatly from place to place and over the lifetime of the instrument.

Parameter/Variable Description/Definition:

CZCS Level 1a data contain at-spacecraft raw radiance counts with calibration and Earth location information included. The data is subsampled every 4th line and every 4th pixel to yield an effective resolution of 4 km. Visible and infrared radiances were measured in six spectral channels. The spectral region and band widths of the six channels and primary use of each are indicated in the following table:


Channel	 	Spectral Band	        Primary purpose	

1		  433 - 453		Chlorophyll absorption
2		  510 - 530		Chlorophyll correlation
3		  540 - 560		Yellow substance (Gelbstoff)
4		  660 - 680		Aerosol correction
5		  700 - 800		Land/cloud flag
6		  10.5 - 12.5 microns	Surface temperature; failed shortly after launch

CZCS Level 2 data is based on derived relationships that compute 6 geophysical parameters from the radiance counts detected by the instrument. The six geophysical parameters are the normalized water-leaving radiance at 443, 520, and 550 nm; the aerosol radiance at 670 nm; the chlorophyll (and associated phytoplankton pigments) concentration; and the diffuse attenuation coefficient measured at 490 nm, K(490). The resolution of the Level 2 data is the same as that for the Level 1a data, 4 km.

Unit of Measurement:

Level 1 Calibrated radiances were measured in units of mW/( with 1x1 km resolution.

Data Source:

CZCS was orbited aboard the Nimbus-7 satellite.

HDF Data Format:

The CZCS Level 1a and Level 2 data are available from the DAAC in two data formats: HDF, the standard data format of the entire Goddard EOSDIS Version 0 (V0) and the SeaWiFS Project;and DSP, a user-interactive satellite data analysis package that was developed at the Rosenstiel School of Marine and Atmospheric Sciences (University of Miami). DSP operates on either DEC-VAX or Unix Workstation computers. Most users will access these data sets in the HDF format, which is described here.Information on DSP may be obtained from Robert H. Evans ( at the University of Miami. See below for a brief description of how the CZCS data were transformed through various data formats to their current status as HDF files.

HDF was developed by the National Center for Supercomputing Applications (NCSA) Software Development Group. Additional explanation of HDF can be found at the HDF Web site. HDF provides several different "data models" which can be used to store data products. The data models currently provided by HDF included Scientific Data Sets (SDS), Raster Image Sets (RIS), Vdatas, and Vgroups.

Each CZCS Level 1a data file contains 10 Scientific Data Sets in two Vgroup files, one for radiance data and one for navigational data.54 global attributes are stored in a metadata file. The 10 scientific data sets are described as follows:


	Subsampled Band 1 (433-453 nm) radiance counts
	Subsampled Band 2 (510-530 nm) radiance counts
	Subsampled Band 3 (540-560 nm) radiance counts	 
	Subsampled Band 4 (660-680 nm) radiance counts 
	Subsampled Band 5 (700-800 nm) radiance counts
	Subsampled Band 6 (10.5-12.5 microns) radiance counts
	Control Point Rows
	Control Point Columns	

In a CZCS Level 2 data file, the radiance counts have been converted to geophysical parameters. Each of these geophysical parameters is stored in a Scientific Data Set, as follows:


	Normalized water-leaving radiance, 443 nm
	Normalized water-leaving radiance, 520 nm
	Normalized water-leaving radiance, 550 nm
	Aerosol radiance, 670 nm
	Chlorophyll and associated pigment concentration
	Diffuse attenuation coefficient, 490 nm		
	Control Point Rows
	Control Point Columns

The 54 global attributes, which are common to a Level 1a data file and the associated Level 2 data file, are listed below for an example scene.

     Attribute Product Name has the value : C1985119202621.L1A_GAC 
     Attribute Title has the value : CZCS Level-1A Data 
     Attribute Data Center has the value : NASA/GSFC DAAC 
     Attribute Station Name has the value : Wallops Flight Facility 
     Attribute Station Latitude has the value : 37.927200 
     Attribute Station Longitude has the value : -75.475304 
     Attribute Mission has the value : Nimbus CZCS 
     Attribute Mission Characteristics has the value : Nominal orbit: inclination = 99.3
     (Sun-synchronous); node = 11:52 a.m. local (ascending); eccentricity = < 0.0009;
     altitude = 955 km; ground speed = 6.4km/sec 
     Attribute Sensor has the value : Coastal Zone Color Scanner (CZCS) 
     Attribute Sensor Characteristics has the value : Number of bands = 6; number of active
     bands = 6; wavelengths per band (nm)= 443, 520, 550, 670, 750, 11500; bits per pixel = 8;
     instantaneous field-of-view = .865 mrad; pixels per scan = 492; scan rate = 8.08/sec;
     sample rate = 3975/sec 
     Attribute Data Type has the value : GAC 
     Attribute Replacement Flag has the value : ORIGINAL 
     Attribute Input Files has the value : c85119202621.ni7 
     Attribute Start Time has the value : 1985119202621797 
     Attribute End Time has the value : 1985119202722043 
     Attribute Scene Center Time has the value : 1985119202651920 
     Attribute Start Year has the value : 1985 
     Attribute Start Day has the value : 119 
     Attribute Start Millisec has the value : 21 
     Attribute End Year has the value : 1985 
     Attribute End Day has the value : 119 
     Attribute End Millisec has the value : 22 
     Attribute Start Node has the value : ascending 
     Attribute End Node has the value : ascending 
     Attribute Sensor Tilt has the value : 20 
     Attribute Orbit Number has the value : 32890 
     Attribute Gain has the value : 1 
     Attribute Ozone has the value : 433 
     Attribute Status has the value : Approved 
     Attribute Pixels per Scan Line has the value : 492 
     Attribute Number of Scan Lines has the value : 122 
     Attribute LAC Pixel Start Number has the value : 1 
     Attribute LAC Pixel Subsampling has the value : 4 
     Attribute Scene Center Scan Line has the value : 61 
     Attribute Latitude Units has the value : degrees North 
     Attribute Longitude Units has the value : degrees East 
     Attribute Scene Center Latitude has the value : 43.353191 
     Attribute Scene Center Longitude has the value : -139.058334 
     Attribute Upper Left Latitude has the value : 42.431637 
     Attribute Upper Left Longitude has the value : -153.757706 
     Attribute Upper Right Latitude has the value : 47.043640 
     Attribute Upper Right Longitude has the value : -125.050400 
     Attribute Lower Left Latitude has the value : 39.272713 
     Attribute Lower Left Longitude has the value : -151.812469 
     Attribute Lower Right Latitude has the value : 43.639820 
     Attribute Lower Right Longitude has the value : -124.580383 
     Attribute Northernmost Latitude has the value : 47.043640 
     Attribute Southernmost Latitude has the value : 39.272713 
     Attribute Westernmost Longitude has the value : -153.757706 
     Attribute Easternmost Longitude has the value : -124.580383 
     Attribute Start Center Latitude has the value : 45.027626 
     Attribute Start Center Longitude has the value : -139.717209 
     Attribute End Center Latitude has the value : 41.648243 
     Attribute End Center Longitude has the value : -138.417877

Related Datasets:

Other ocean color data sets include SeaWiFS, MOS-PRIRODA, OCTS and some airborne data collected by NASA and NOAA. Many investigations benefit from correlating CZCS data with available in situ and sea surface temperature data.

More information is on our Satellite Based Ocean Color Instruments page.

10. Data Manipulations:

Derivation Techniques and Algorithms:

The most significant problems encountered in analyzing the CZCS data are in the correction for atmospheric dispersion, and differentiating between pigment concentrations and suspended inorganic substances. In the visible portion of the spectrum, the largest contribution to the signal received by CZCS was from the atmosphere. Rayleigh and aerosol scattering in the atmosphere require accurate correction routines to eliminate their contribution, which then allows a high degree of accuracy in the determination of oceanic pigment concentration and diffuse attenuation coefficient.

The calibration procedure is quite complex, and will not be discussed in detail here. The Rayleigh component is assumed essentially constant, allowing it to be subtracted from the signal. Aerosol scattering is variable, and is estimated by assuming that the red region of the spectrum is completely absorbed by the ocean surface and therefore returns no signal to the instrument. From this assumption, aerosol scattering can be calculated for the rest of the visible spectrum. References 11.2.b and 11.2.c describe these principles in detail. The final data are in the form of calibrated radiances.

Photosynthetic pigment concentration algorithms were used to reduce the data produced from the Level 1 (and Level 1a) radiance data to Level 2 pigment concentration. These algorithms use radiance data ratios to determine concentrations. Channels 1 and 3 were used for lower concentrations (less than 1.5 mg/m**3) and channels 2 and 3 for higher concentrations. These algorithms also account for the Rayleigh and aerosol atmospheric scattering present by employing empirical coefficients in the equations for pigment concentration.

Data Processing Sequence:

Processing Steps (and Datasets):

At Goddard Space Flight Center the data were converted from voltages to radiances for bands 1 through 5, and to equivalent blackbody temperatures for band 6. The Level 1 radiance data were used to produce black and white images. Algorithms developed by the CZCS Nimbus Experiment Team were then applied to produce Level 1a and 2 data of suspended and dissolved materials on the water. These algorithms have continued to evolve since the beginning of data collection, especially for retrieval of water properties in sediment-laden coastal regions.

Processing Changes:

The entire CZCS digital archive was later converted from the original 1600-bpi magnetic tape to Sony digital optical disk at Goddard Space Flight Center. 38,000 nine track magnetic tapes were read 24 hours per day, 7 days per week for 18 months in order to transfer the data to approximately 185, 12 inch optical discs. The newly archived data format was nearly identical to the Calibrated Radiance and Temperature Tape (CRTT) product. These optical platters are now stored at the Goddard DAAC and remain a primary archive for the CZCS data set.

Researchers at the University of Miami Rosenstiel School of Marine and Atmospheric Science (RSMAS) converted the data on the optical platters into the "DSP" format for the purposes of further analysis. This format was in use by the oceanographic community until the conversion to the HDF format, which has been adopted by the SeaWiFS Project and the Earth Observing System, and the Goddard DAAC, including the Ocean Color DAAC. Consult RSMAS for further information on the DSP format. The description above applies to CZCS HDF files.

11. Errors:

Quality Assessment:

Some Level 1 scenes were flagged as containing unreliable data and were not included in the Level 3 composites but are still available from the Goddard DAAC. During ingest into the Goddard DAAC, metadata contained in the Level 1 files were accessed and used to produce a comprehensive and consistent database for all CZCS holdings. Many duplicate files and errors were eliminated in this first effort.In 1996 the metadata themselves were reviewed uncovering several types of navigational errors. Based on that analysis the database was updated and corrected again. The corrected data base entries now provide the framework for operational Browse and request processing.

Data Validation by Source:

In situ data useful for CZCS applications are available from SeaBASS ( SeaBASS is a product of the Calibration/Validation element of the NASA Sea-viewing Wide Field-of-view Sensor (SeaWiFS) Project. SeaBASS provides an interface to the Project's holdings of bio-optical and laboratory instrument calibration data. The interface allows access to over 1000 individual data files provided by numerous investigators.

Currently, the SeaBASS bio-optical holdings include radiometric data and in situ pigments collected as part of these experiments:

       Nimbus Experiment Team (NET) 
       U.S. Joint Global Ocean Flux Study (JGOFS) 
       Bermuda Bio-Optical Program (BBOP) 
       CHORS/British Ocean Flux Study (BOFS) 
       Bermuda Area Time Series (BATS) 
       Hawaii Ocean Time Series (HOTS) 
       Tokyo Bay 
       CALCOFI Cruises 
       NORTH SEA Experiments 
       Chesapeake Bay 

SeaBASS also includes instrument calibration data collected as part of SIRREX-1, SIRREX-2, and eventually SIRREX-3/4/5. New data sets are received and archived on a regular basis. SeaBASS is described in much greater detail in Volume 20 of the SeaWiFS Technical Report Series (NASA Tech. Memorandum 104566). You may request a copy of Vol. 20 via the SeaWiFS TM Series order form from the Goddard DAAC Helpdesk via email or phone:, (301) 614-5224.

Confidence Level/Accuracy Judgement:

CZCS performed better than its design requirements for signal-to-noise ratio in all channels. The table below shows the minimum signal-to-noise ratio specified for the instrument at its most sensitive gain setting. In the worst case, the chlorophyll concentration can be determined within a factor of 2 of the actual concentration.
     Channel/ Signal/Noise
     Band    Ratio (mW/cm**2-ster)   Radiance        NETD    Temp

     1       150                     5.41
     2       140                     3.50
     3       125                     2.86
     4       100                     1.34
     5       100                     10.8
     6       N/A                     N/A             0.220K  270K

Measurement Error for Parameters and Variables:

No additional measurement error assessments are available.


Additional Quality Assessments:

No additional quality assessments are available.

Data Verification by Data Center:

The Goddard DAAC has not performed data verification on the CZCS dataset.Only metadata verification has been performed.


12. Notes:

Known Problems with the Data:

The internal metadata in the header and trailer documentation records for Level 1 files is known to be erroneous in several instances. The Goddard DAAC's data base has been corrected, but the individual header and trailer records have not been corrected.

Any other Relevant Information about the Study:

Assumptions in the atmospheric correction of the data during processing resulted in an accuracy of 35% in ocean color measurements in Case I waters (chlorophyll and associated pigments determine the reflectance) and within a factor of 2 generally.

Due to the limited duty cycle (10%) and the non-uniform coverage, sampling was highly skewed. Temporal sampling frequency also varied, resulting in potential errors. An in depth overview of the entire history of the CZCS Project is included in Reference 4, below.

13. Application of the Dataset:

(Please refer to Section 4.)


14. Future Dataset Plans:

The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) is scheduled to launch in 1997 as a follow-on to CZCS. SeaWiFS data will be distributed to authorized users by the Goddard DAAC.

Users should refer to the SeaWiFS Project homepage for the latest information on SeaWiFS:

15. References

  1. "CZCS Sensor Guide Document", prepared by the Distributed Active Archive Center, NASA Goddard Space Flight Center, Greenbelt, Maryland, 1995.
  2. "The Living Ocean: Observing Ocean Color From Space", NASA Publication PAM-554, Goddard Space Flight Center, Greenbelt, Maryland, 1993.
  3. "Coastal zone color scanner 'system calibration': A retrospective examination." R.H. Evans & H.R. Gordon, Journal of Geophysical Research, Vol.99. No. C4, pages 7293-7307, April 15, 1994.
  4. "Coastal Zone Color Scanner", European Space Research Institute, Frascati, Italy.
  5. Nimbus 7 Coastal Zone Color Scanner (CZCS) Level 1 Data Product Users' Guide NASA TM 86203, S.P. Williams, E.F. Szajna and W.A. Hovis. Goddard Space Flight Center, Greenbelt, MD 20771. July, 1986, 53 pages.

Journal Articles and Study Reports:

The April 15, 1994 issue of the Journal of Geophysical Research (Volume 99, Number C4) contains a Special Section entitled "Ocean Color From Space: A Coastal Zone Color Scanner Retrospective."


16. Related Software:

There are two primary ways in which CZCS Level 1a and Level 2 data may be examined and processed. The appropriate software package to use depends on the data format. If the data is in DSP format, CZCS Level 1a and 2 DSP images can be converted to the SEAPAK format using the SEAPAK package, which is also used for CZCS Level 1 data processing. The Goddard DAAC provides a mirror site for the distribution of SEAPAK CZCS data processing software.

If the CZCS data is in the HDF format, the appropriate package to use for processing and analysis is SeaDAS. Subsequent to the information provided on SEAPAK is a brief description of SeaDAS and links to sites with more detailed information.


SEAPAK is a user-interactive satellite data analysis package that was developed at the NASA/Goddard Space Flight Center. The primary application of SEAPAK is for the processing and interpretation of Level 1 Coastal Zone Color Scanner (CZCS) and Advanced Very High Resolution Radiometer (AVHRR) data.

Two versions of the SEAPAK CZCS processing software are available free of charge online and on tape from the Goddard DAAC. PC-SEAPAK runs on PC-AT, 386, or 486 class machines. UNIX-SEAPAK operates only on SGI's Unix Workstation. Besides including most major programs in PC-SEAPAK to process CZCS and AVHRR satellite data, Unix-SEAPAK also includes programs to handle ancillary data.

Note: The DAAC is a mirror site to We do not support the maintenance and development of SEAPAK. We will provide timely updates and information to directly contact the authors.

Software System Requirements:

PC-SEAPAK runs on PC-AT, 386, or 486 class machines. UNIX-SEAPAK operates on SGI Unix Workstations only.

To be able to use all of PC-SEAPAK's graphics functions, you will need to have a Matrox graphics board installed on your PC. Even if you do not have this board, the whole PC-SEAPAK package should be installed. It will work on a PC without the board but the you won't be able to run the display related programs. To request a non-graphical version of PC-SEAPAK on diskettes, contact the Goddard DAAC Helpdesk:

Software Documentation:

Copies of the 350 page PC-SEAPAK User's Guide are available online and in hardcopy from the Goddard DAAC Helpdesk. This documentation is intended to be used by both UNIX and PC customers and it is the only SEAPAK documentation available from the Goddard DAAC.

PC-SEAPAK User Guide

Software Access and Installation:


The PC version of SEAPAK is available through FTP.

FTPPC-SEAPAK directory

In this directory, you will find four compressed files and one program to decompress those files as well as three update files:
The compressed file that contains all the PC-SEAPAK version 4.0 programs data base file (in 5-minute resolution)
The compressed file that contains the eight CIA world data base files.
The compressed file that contains nine PCTOMS data base files.
The compressed file that contains HALO88 font files and the driver program for the MVP-AT image board
The decompressing program to be used on PC to decompress those compressed zip files.

These update files have to be restored (in any temporary directory using 'pkunzip') and installed (copied) IN ORDER into the SEAPAK directory after you have installed the original PC-SEAPAK 4.0.


Download all of these files to the PC first. Then run PKUNZIP to decompress all the ZIP files. Type PKUNZIP at the DOS prompt and you will get a detailed description about how to use this command.

For example, to decompress all files in 'SEAPAK.ZIP' to the directory 'D:\SEAPAK', just type 'PKUNZIP SEAPAK.ZIP D:\SEAPAK'. All other compressed files should be decompressed the same way. It is recommended that you decompress different zip files into different directories. After all compressed files are restored, you need set up the SEAPAK environmental variable, modify SEAPAK.FIG file if necessary, run the programs SPKSETUP and INIT.

For further information, read SYSTEM ENVIRONMENT: SOFTWARE section in the PC-SEAPAK User's Guide.


The UNIX version of SEAPAK is available through FTP.


The files 'ANNOUNCEMENT', 'README.SEAPAK.PLEASE!' in the UNIX SEAPAK directory contain information about how to install UNIX-SEAPAK. Because there is no UNIX-SEAPAK User's Guide available, UNIX SEAPAK users should request a copy of the PC-SEAPAK User's Guide from the Goddard DAAC Helpdesk:

If you have any problem or need assistance with installing or using SEAPAK, contact:

Gary Fu

For more information on scientific applications of the SEAPAK and DSP image processing systems contact:

Dr. Charles McClain
SeaWiFS Project Scientist

Dr. Robert Evans, University of Miami's Rosenstiel School of Marine Sciences


SeaDAS was developed for the processing of SeaWiFS ocean color data in the HDF format. As CZCS Level 1a and Level 2 data has also been converted to HDF, SeaDAS may also be used to process these data types. SeaDAS is a comprehensive image analysis package for processing, displaying, analyzing, and performing quality control on all SeaWiFS (Sea-viewing Wide Field-of vew Sensor) data products (L0, L1A, L2, L3 Binned, L3 SMI, L1A-, L2-, L3-Browse) and ancillary data (Wind, Pressure, Humidity and OZONE) from NMC (National Meteorological Center and TOVS (TIROS Operational Vertical Sounder). All SeaDAS source code is freely available for download via FTP.

The use of SeaDAS requires an IDL license.

SeaDAS Configuration and Requirements

SeaDAS is being developed on the Silicon Graphics Inc.'s (SGI) Indigo2 and has been successfully ported to a SUN Sparc 10 workstation. The Interactive Data Language (IDL) from Research System Inc. (RSI) is used to build all the GUI and display related programs in SeaDAS. It is REQUIRED for SeaDAS and has to be purchased from RSI. The Hierarchical Data Format (HDF) libraries from National Center for Supercomputing Applications (NCSA) are also required to build certain SeaDAS programs. However since the necessary HDF libraries (does not include HDF utilities) have been included in SeaDAS, the users do not need to download it from NCSA. C, FORTRAN77, and IMAKE from the vendors are required ONLY if you want to modify the source and rebuild the executable. Other platforms and other versions of C and FORTRAN compiler have not been ported or tested on the current version of SeaDAS. SeaDAS development team will try to port SeaDAS to other platforms in the future. In the meantime, since all the source codes are available, if any group is interesting in porting SeaDAS to other platforms, the development team will be happy to give any kind of assistance.

Recommended Hardware Configuration

  • Platform: SGI Indigo2/SUN Sparc 10 or larger
  • Memory: 96 MB
  • Disk: 3 GB
  • Tape Drive: 4MM(DAT) or 8mm Exabyte
  • Display: 19" Console or X-terminal, 1280x1024 resolution, 8-bit, 256 colors

Software Requirements:

  • Operating System: IRIX 5.3 (SGI) or Solaris 2.4 (SUN)
  • Languages: C (SGI V3.19, SUN V 3.0.1), FORTRAN(SGI V 4.0.2, SUN V 3.0.1), IDL 4.0.1
  • Software Libraries: HDF 3.3r4p4 (included in SeaDAS)


Obtaining SeaDAS

SeaDAS is available for download via anonymous FTP from The /seadas directory contains following compressed tar files:

  • seadas_src.tar.Z : SeaDAS source codes only (does not include seadas_data.tar.Z)
  • seadas_data.tar.Z : SeaDAS required data files for L1, L2, and L3 processing
  • seadas_all.sgi.tar.Z : Complete SeaDAS (source and binary files) for SGI workstation (does not include seadas_data.tar.Z)
  • seadas_all_sun.tar.Z : Complete SeaDAS (source and binary files) for SUN workstation (does not include seadas_data.tar.Z)
  • seadas_demo.tar.Z : sample files for testing and demos

To download SeaDAS files, go to the SeaDAS ftp site.

We may also create SeaDAS on 4mm (DAT) or 8mm tape for those users who do not have Internet access. Please send your request to

SeaDAS Installation

After you get the SeaDAS compressed tar files, following the steps to install it into your system.

1. Create SeaDAS root directory
      mkdir seadas

2. Change to the SeaDAS root directory
      cd seadas

3. Uncompress/extract SeaDAS application TAR file 
          zcat seadas_src.tar.Z | tar xvf -
     OR   zcat seadas_all.tar.Z | tar xvf - (for binary TAR)

4. Uncompress/extract SeaDAS data TAR file
   (Required only for L1, L2, and L3 processing routines)
          zcat seadas_data.tar.Z | tar xvf -

5. Run SeaDAS setup program

6. Activate setup file
      source ./config/seadas.env
            (this should be added to your .cshrc file)

*** If using seadas_src.tar.Z ***
*                               *
* 7. Prepare for installation   *
*     make pre_install          *
*                               *
* 8. Make installation          *
*     make install              *
*                               *
*** If using seadas_src.tar.Z ***

9. Start SeaDAS
      seadas menu

For further information on SeaDAS, contact:
Dr. Charles R. McClain or Dr. Kevin Arrigo
SeaWiFS Project
Code 970.2
NASA Goddard Space Flight Center
Greenbelt, MD20771

17. Data Access:

Contacts for Archive/Data Access Information:

Goddard DAAC Education and Outreach Website

Goddard DAAC Helpdesk
Code 610.2
NASA Goddard Space Flight Center
Greenbelt MD 20771 USA
(301) 614-5224
(301) 614-5268 fax

Archive Identification:

NASA Goddard Space Flight Center DAAC


Procedures for Obtaining Data:

The Goddard DAAC is the central archive and distribution facility responsible for providing access to the entire CZCS data set. The entire collection of Coastal Zone Color Scanner (CZCS) ocean color data and images is available on-line via the World Wide Web in the Data Section of the NASA Goddard DAAC Education & Outreach Web site.

Users may view Level 2 browse images of 59,337 CZCS files and place FTP or tape orders with the Goddard DAAC for those CZCS data products they desire. Each Level 2 browse file maps to corresponding Level 1 and 1a files. All Level 1a and 2 files are also available via anonymous ftp. CZCS Level 1 files are orderable via the Browser but do not reside online due to the size of the Level 1 collection.


Data Archive Status/Plans:

Archive of the CZCS data set at the Goddard DAAC is complete. Ocean Color website documentation and access development is also nearing completion. Future activities will be dedicated to the support of SeaWiFs archive and distribution starting in calendar year 1997.


18. Output Products and Availability:

Tape Media:

8mm tape (8200 and 8500 bpi)
4mm tape (60m and 90m)

Other Products:

Electronic transfer (ftp), files in DSP or HDF format

19.Glossary of Terms

Calibration: the adjustment or systematic standardization of the output of a quantitative measuring instrument or sensor.
Chlorophyll: any of a group of related pigments found in photosynthetic organisms.
Contemporaneous: originating, existing or happening during the same period of time.
Dynamic Range: the range between the maximum and minimum amount of input radiant energy that an instrument can measure.
Gelbstoff: Dissolved and suspended inorganic matter, commonly found in river discharge, which gives it a yellowish color. (from German: "yellow substance").
Infrared Light: electromagnetic radiation having wavelengths longer than red light (7700 angstroms) but less than radio waves (~.1 meter).
Nadir: the point on the Earth directly below an orbiting satellite.
Photosynthesis: the process by which chlorophyll-containing cells in plants convert incident light to chemical energy and synthesize organic compounds from inorganic compounds, especially carbohydrates, from carbon dioxide and water, with the simultaneous release of oxygen.
Phytoplankton: drifting, often microscopic, oceanic plants which conduct the process of photosynthesis.
Primary productivity: the rate at which organic carbon is produced photosynthetically.
Radiometer: a device that detects and measures electromagnetic radiation in discrete spectral bands of the electromagnetic spectrum.
Spatial Resolution: the size of the smallest object recognizable using the detector.
Spectral Band: a narrow range of the electromagnetic spectrum.
Spectral Response: the relative amplitude of the response of a detector vs. the frequency of incident electromagnetic radiation.
Visible Light: electromagnetic radiation with wavelength in the 3900 to 7700 angstrom range.
Zenith: the "sky" point located directly above an Earth-based sensor.

20. List of Acronyms:

AVHRR: Advanced Very High Resolution Radiometer
CZCS: Coastal Zone Color Scanner
DST: Data Support Team
EOSDIS: Earth Observing System Data and Information System
ESDIS: EOSDIS Data and Information System
ESRIN: European Space Research Institute
IFOV: Instantaneous Field of View
MODIS: Moderate Resolution Imaging Spectroradiometer
Nimbus: NASA Meteorological Satellites (1 through 7) [not an acronym]
NOAA: National Oceanic and Atmospheric Administration
SeaWiFS: Sea-viewing Wide Field-of-view Sensor

Change History

Version 2.0
Version baselined on addition to the GES Controlled Documents List, Feb 18, 2000.
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