The Landsat 7 Processing System (LPS) Level Zero-R Science Products

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

1

The Landsat 7 Mission
•
•
•
•
•
•
•

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


2

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

3

The ETM+ Instrument Data
• Eight bands
– Six 30m-resolution spectral bands
•
•
•
•

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

4

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

5

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

6

The LPS Moving Window Display (MWD)


7

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

8

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:
–
–
–
–
–
–

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)


9

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

10

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

11

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

12

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


13

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
–
–
–
–

Format 1 only
One native HDF RIS24 true color image
Made from three of the five format 1 spectral bands
JPEG Compressed images


14

LPS Browse File (Hudson Bay)


15

Format 1
• Six Band files
– Bands 1-5 and 6L

•
•
•
•

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

16

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

•
•
•
•
•

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


17

The LPS Product File Set


18

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

19

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

20

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


21

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


22

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


23

L0R Distribution Product File Set


24

The Landsat 7 Processing System (LPS) Level Zero-R Science Products

Recomendados

Recomendados

Más contenido relacionado

La actualidad más candente

La actualidad más candente (20)

Similar a The Landsat 7 Processing System (LPS) Level Zero-R Science Products

Similar a The Landsat 7 Processing System (LPS) Level Zero-R Science Products (20)

Más de The HDF-EOS Tools and Information Center

Más de The HDF-EOS Tools and Information Center (20)

Último

Último (20)

The Landsat 7 Processing System (LPS) Level Zero-R Science Products