MODIS Nomenclature
Last Update: August 3, 2006
Processing Levels
Once on the ground, data are processed to varying stages. Users should
choose the data that meets their needs.
Level 0
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Raw instrument data at original resolution, time ordered, with duplicate
packets removed.
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Level 1A
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Reconstructed instrument radiance data (in sensor counts) at original
resolution with calibration data appended. Geolocation data are stored
in a separate file.
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Level 1B
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Level 1A data converted into calibrated radiances.
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Level 2
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Derived geophysical parameters at the same resolution and location as
the Level 1 data. In other words, data are in the instrument's swath
geometry. For MODIS, each scene consists of 5 minutes of viewing by
the instrument (approximately 203 scans).
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Level 2G
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MODIS Land products are processed into an intermediary step for storing
information concerning Level 2 observations that fall within each
Level 3 grid cell (includes the geophysical parameter and the sensing
geometry for each Level 2 observation). The observations stored in the
Level 2G products are examined by the Level 3 processes to extract the
most relevant observations for each grid cell.
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Level 3
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Geophyscial parameters that have been spatially or temporally resampled
into an Earth-located grid using a common projection.
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Level 4
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Model output and/or results of lower level data that are not directly
derived by the instrument.
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Data Collections
Collections, or versions, indicate reprocessings of the data. The higher
the collection number, the better the quality of the data. Each MODIS
product and algorithm underwent improvements before each reprocessing. The
following is a brief synopsis of the MODIS collections.
Terra Collection 1
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Original, at-launch version. Most products released at beta quality.
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Terra Collection 2
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Never produced.
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Terra Collection 3
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Partial mission reprocessing to incorporate calibration and algorithm
improvements. Most products released at provisional quality. Some
products validated.
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Terra Collection 4
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Entire mission reprocessing with calibration stabilization and
refinements to the geophysical algorithms. Most products validated.
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Terra Collection 5
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Entire mission reprocessing with latest calibration improvements and
algorithm refinements. Products validated.
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Aqua Collection 3
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Original, at-launch version, using MODIS algorithms at the maturity of
Terra Collection 3. Thus, most Aqua products were released at
provisional quality.
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Aqua Collection 4
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Entire mission reprocessing with calibration stabilization and
refinements to the geophysical algorithms. Most products validated.
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Aqua Collection 5
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Entire mission reprocessing with latest calibration improvements and
algorithm refinements. Products validated.
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Data Maturity
Beta
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Early release product with known problems and frequent algorithm
updates. Scientific use of the product is not recommended.
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Provisional
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Some incremental improvements are still occurring, although QA tests
show stability in the product. Scientific use should only be done
with caution and careful reference to QA statements provided with the
product.
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Validated
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Estimates of product accuracy and uncertainty have been obtained through
comparisons with independent data. The results of validation are
published in the peer-reviewed literature. The validation data are
available. Scientific use is recommended and encouraged commensurate
with the stage of validation achieved.
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Stage 1 Validation
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Product accuracy has been estimated using a small number of independent
measurements obtained from selected locations and time periods and
ground-truth/field program efforts.
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Stage 2 Validation
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Product accuracy has been assessed over a widely distributed set of
locations and time periods via several ground-truth and validation
efforts.
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Stage 3 Validation
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Product accuracy has been assessed, and the uncertainties in the product
well-established, via independent measurements made in a systematic and
statistically robust way that represents global conditions.
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Generalized Filenaming Convention
MOD01.A2002032.1015.003.2002034184356.hdf
aaaaa bbbbccc dddd eee fffffffffffff ggg
a) MODIS product short name, e.g. "MOD01" refers to the MODIS Level 1A
Radiance product. "MOD" signifies Terra/MODIS, whereas "MYD" signifies
Aqua/MODIS.
b) Year in which data was collected by the instrument, e.g. 2002.
c) Day on which data was collected by the instrument, given in Day of Year.
For example, "032" is February 1st, i.e. the 32nd day of the year.
d) Time at which data was collected, given in Universal Time Coordinate
(UTC) or Greenwich Mean Time (GMT).
e) Collection (version) number.
f) Production date and time, given in year, day-of-year, hours, minutes,
and seconds, in the form yyyydddhhmmss.
g) File type extension, e.g. "hdf" is Hierarchical Data Format. All MODIS
data are available in HDF format.
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