The Landsat 7 Processing System (LPS) Level Zero-R Science Products
1. The Landsat 7 Processing System
( LPS )
Level Zero-R Science Products
Michael R. Reid
Computer Sciences Corporation
Mike.Reid@gsfc.nasa.gov
ESDIS HDF-EOS Workshop IV
Landover, Maryland, September 20, 2000
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2. The Landsat 7 Mission
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The latest in the Landsat series
Joint operation between NASA and USGS
Global coverage in 8 bands
Sun-synchronous orbit
Landsat 7 successfully launched in April 1999
Now fully operational
Data products provided by the USGS’ EROS
Data Center (EDC) in Sioux Falls, SD
ESDIS HDF-EOS Workshop IV
Landover, Maryland, September 20, 2000
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3. Earth Coverage
• Enhanced Thematic Mapper Plus (ETM+) is
the only science instrument
– Images the Earth in 185 km wide swaths
– Images in eight bands
• Image data are fitted onto the Worldwide
Reference System (WRS) grid
– WRS grid consists of 185 km × 170 km scenes
– ETM+ images a WRS scene with 375 scans
• WRS scenes overlap
ESDIS HDF-EOS Workshop IV
Landover, Maryland, September 20, 2000
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4. The ETM+ Instrument Data
• Eight bands
– Six 30m-resolution spectral bands
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Bands 1-5 (range λ = 0.45…1.75 µm)
Band 7 (λ = 2.09-2.35 µm)
6,600 pixels per scan data line
16 data lines per scan
– One 60m-resolution thermal band
• Band 6 (λ = 10.4-12.5 µm)
• 3,300 pixels per scan data line
• 8 data lines per scan
– One 15m-resolution panchromatic band
• Band 8 (λ = 0.52-0.90 µm)
• 13,200 pixels per data line
• 32 data lines per scan
ESDIS HDF-EOS Workshop IV
Landover, Maryland, September 20, 2000
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5. Landsat 7 Processing System (LPS)
• Developed at NASA/GSFC for the EDC
• Part of the Landsat 7 Ground System
• Performs the first stage of Level 0 processing
– Aligns bands (forward and reverse scans)
– Does not apply corrections or calibrations
– Does not perform rectification
• Produces HDF-EOS science data products on a
subinterval basis
• Runs on a high-end SGI™ system
ESDIS HDF-EOS Workshop IV
Landover, Maryland, September 20, 2000
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6. LPS Processing
• Divides the subintervals into sets of contiguous
WRS scenes
• Geolocates the scenes
• Produces viewable, multi-band, color browse
images on a WRS scene basis
• Performs automatic cloud cover assessment
(ACCA) on a WRS scene basis
• Displays a Moving Window Display to the user
ESDIS HDF-EOS Workshop IV
Landover, Maryland, September 20, 2000
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7. The LPS Moving Window Display (MWD)
ESDIS HDF-EOS Workshop IV
Landover, Maryland, September 20, 2000
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8. LPS Processing continued…
• Receives data on two channels (“format 1” and
“format 2”)
• Decodes the downlinked raw telemetry
• Processes the two formats separately
• Constructs an image in each band of the
“swath” on the Earth’s surface covered during
a contact
• Divides the swath into subintervals
ESDIS HDF-EOS Workshop IV
Landover, Maryland, September 20, 2000
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9. The LPS Data Products
• LPS products generated on a subinterval basis
• Format 1 and Format 2 are separate file sets
• The LPS Product file sets include:
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Band files (Swath files)
Internal Calibrator (IC) data files
Mirror Scan Correction Data (MSCD) files
Payload Correction Data (PCD) files
Metadata files
Multi-Band Browse files (format 1 only)
ESDIS HDF-EOS Workshop IV
Landover, Maryland, September 20, 2000
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10. The Band Files — Swaths
• Image data stored in HDF-EOS Swaths
– One Swath per file
• Bands 1-5 & 7 files are up to about 1.2 Gb in size
• Band 6 files are up to about 295 Mb in size
• Band 8 data are huge, won’t fit in single files
– Up to about 4.6 Gb of data in a 35-scene
subinterval
– HDF 4 limits file sizes to 2 Gb
– Written to up to three separate swaths in separate
segment files
ESDIS HDF-EOS Workshop IV
Landover, Maryland, September 20, 2000
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11. The Band Files — Geolocation
• Geolocation structures
– Uses HDF-EOS Index map to link WRS scene
corner lon/lat coordinates to the Swath
• Full scenes from 30m-res. bands are always 6,000 data
lines
• Partial scenes at the beginnings and ends of subintervals
are of irregular sizes
– Uses Time Geolocation field to temporally locate
scans in the Swaths
• HDF-EOS Geolocation structures also used to
store other ancillary data
ESDIS HDF-EOS Workshop IV
Landover, Maryland, September 20, 2000
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12. The Internal Calibrator (IC) Files
• Contain lamp and shutter data for spectral
bands
• Contain blackbody radiance and shutter data
for thermal band (band 6)
• One file for each format
– Separate HDF-EOS Swath for each band
• One data set per scan
• Data located by Time only using HDF-EOS
Geolocation structure
ESDIS HDF-EOS Workshop IV
Landover, Maryland, September 20, 2000
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13. Mirror Scan Correction Data (MSCD) Files
• Mainly contain data quality information
• Stored in an HDF-EOS Point
• Located by Time only using HDF-EOS
Geolocation structure
• Format 1 and Format 2 MCSD are identical
except for start and end offsets at the
beginnings and ends of the data
ESDIS HDF-EOS Workshop IV
Landover, Maryland, September 20, 2000
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14. Other LPS Product Files
• Payload Correction Data (PCD) Files
– Contain spacecraft attitude and ephemeris information and
miscellaneous engineering data
– Native HDF Vdata, no HDF-EOS structures
– Format 1 and Format 2 are identical
• Metadata Files
– Format 1 and Format 2 similar, but not identical
– Simple text file in Object Definition Language (ODL) Syntax
• Browse Files
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Format 1 only
One native HDF RIS24 true color image
Made from three of the five format 1 spectral bands
JPEG Compressed images
ESDIS HDF-EOS Workshop IV
Landover, Maryland, September 20, 2000
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15. LPS Browse File (Hudson Bay)
ESDIS HDF-EOS Workshop IV
Landover, Maryland, September 20, 2000
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16. Format 1
• Six Band files
– Bands 1-5 and 6L
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One Internal Calibrator (IC) data file
One Payload Correction Data (PCD) file
One Mirror Scan Correction Data (MSCD) file
One Metadata file
– Includes scene cloud cover assessments
• 1 to 37 Multi-band Browse files
ESDIS HDF-EOS Workshop IV
Landover, Maryland, September 20, 2000
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17. Format 2
• Three Bands, up to five files
– Bands 6H and 7
– Band 8 (High-Resolution Panchromatic Band)
• Written to up to three segment files due to size
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One Internal Calibrator (IC) data file
One Payload Correction Data (PCD) file
One Mirror Scan Correction Data (MSCD) file
One Metadata file
No Browse files
ESDIS HDF-EOS Workshop IV
Landover, Maryland, September 20, 2000
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18. The LPS Product File Set
ESDIS HDF-EOS Workshop IV
Landover, Maryland, September 20, 2000
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19. Level Zero-R Data Subsets
• Single WRS scene products
– One 375 scan subset
– Data fitted to the WRS grid
• Multiple scene products
– Contains several contiguous WRS scenes
• Partial subinterval (a.k.a., floating scene) products
– Similar to the multiple scene products, but not aligned along
WRS rows
• Full subinterval products
– Essentially the full LPS subinterval
ESDIS HDF-EOS Workshop IV
Landover, Maryland, September 20, 2000
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20. Subsetting the LPS Subintervals
• LPS Band and IC files contain geolocated HDF-EOS
Swaths
– Can subset band data by index-mapped WRS scene corner
geographic coordinates or time using HDF-EOS functions
• Band 8 presents a problem due to file segmentation
– Can subset IC data by time using HDF-EOS functions
• MSCD file contains an HDF-EOS Point
– Can subset by time using HDF-EOS functions
• PCD is native HDF and cannot be subsetted using
HDF-EOS functions
ESDIS HDF-EOS Workshop IV
Landover, Maryland, September 20, 2000
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21. LPS Subsetting Difficulties
• Band data Swaths are stored in separate files
• Format 1/Format 2 data offset
• Partial subinterval geolocation
– LPS only computes lon/lat coordinates for WRS
scene corners, not on a scan basis
– Must interpolate subset interval corner coordinates
• Band 8 segmentation
– HDF-EOS does not support file segmentation
ESDIS HDF-EOS Workshop IV
Landover, Maryland, September 20, 2000
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22. Band 8 Subsetting Problem
• Must treat the band 8 segments as completely
separate data sets
• Subsetting out multiple scene or partial
subinterval products from band 8 is especially
complicated if the subset interval spans across
segments
• After subsetting from the two segments, the
data must be concatenated into a single array
ESDIS HDF-EOS Workshop IV
Landover, Maryland, September 20, 2000
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23. Level Zero-R Distribution Product
• Native HDF, no HDF-EOS structures
• Contains data from both Format 1 and Format
2
• Subsets of Band and IC data written to
Scientific Data Sets (SDS)
• Subset of MSCD written to Vdatas
• Complete PCD and Metadatas written to
Vdatas
• Contains Calibration Parameter File (CPF)
• Stores all data in HDF external elements
ESDIS HDF-EOS Workshop IV
Landover, Maryland, September 20, 2000
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24. L0R Distribution Product File Set
ESDIS HDF-EOS Workshop IV
Landover, Maryland, September 20, 2000
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