MOD09GQ v006

MODIS/Terra Surface Reflectance Daily L2G Global 250 m SIN Grid


PI: Eric Vermote

Description

The MOD09GQ Version 6 product provides an estimate of the surface spectral reflectance of Terra Moderate Resolution Imaging Spectroradiometer (MODIS) 250 meter (m) bands 1 and 2, corrected for atmospheric conditions such as gasses, aerosols, and Rayleigh scattering. Along with the 250 m surface reflectance bands are the Quality Assurance (QA) layer and five observation layers. This product is intended to be used in conjunction with the quality and viewing geometry information of the 500 m product (MOD09GA).

Characteristics

Improvements/Changes from Previous Versions

  • Improvements to the aerosol retrieval and correction algorithm along with new aerosol retrieval look-up tables.
  • Refinements to the internal snow, cloud, and cloud shadow detection algorithms. Uses Bidirectional Reflectance Distribution Function (BRDF) database to better constrain the different threshold used.
  • Processes ocean bands to create a new Surface Reflectance Ocean product and provides Quality Assurance (QA) datasets for these bands.
  • Improved discrimination of salt pans from cloud and snow, along with the inclusion of a salt pan flag in the QA band.

Product Maturity

Validation at stage 3 has been achieved for all MODIS surface reflectance products. Further details regarding MODIS land product validation for the MOD09GQ data product is available from the MODIS land team validation site.

Collection and Granule

Collection

Characteristic Description
CollectionTerra MODIS
DOI10.5067/MODIS/MOD09GQ.006
File Size84 MB
Temporal ResolutionDaily
Temporal Extent2000-02-24 to Present
Spatial ExtentGlobal
Coordinate SystemSinusoidal
DatumN/A
File FormatHDF
Geographic Dimensions1200 km x 1200 km

Granule

Characteristic Description
Number of Science Dataset (SDS) Layers8
Columns/Rows4800 x 4800
Pixel Size250 m

Layers

SDS Name Description Units Data Type Fill Value No Data Value Valid Range Scale Factor
num_observations Number of observations per pixel N/A 8-bit signed integer -1 N/A 0 to 127 N/A
sur_refl_b01_1 Surface Reflectance Band 1 N/A 16-bit signed integer -28672 N/A -100 to 16000 0.0001
sur_refl_b02_1 Surface Reflectance Band 2 N/A 16-bit signed integer -28672 N/A -100 to 16000 0.0001
QC_250m_1 Surface Reflectance 250m Quality Assurance Bit Field 16-bit unsigned integer 2995 N/A 0 to 4096 N/A
obscov_1 Observation coverage Percent 8-bit signed integer -1 N/A 0 to 100 0.01
iobs_res_1 Observation number N/A 8-bit unsigned integer 255 N/A 0 to 254 N/A
orbit_pnt_1 Orbit pointer N/A 8-bit signed integer -1 N/A 0 to 15 N/A
granule_pnt_1 Granule pointer N/A 8-bit unsigned integer 255 N/A 0 to 254 N/A

The Number of Science Dataset Layers is a minimum of 8. If the "L2G Storage Format" metadata value is "full" additional data layers are present with the suffix _f. If the "L2GStorageFormat" metadata value is "compact" additional data layers are present with the suffix _c.

Product Quality

The QC_250m_1 layer is stored in an efficient bit-encoded manner. The unpack_sds_bits executable from the LDOPE Tools is available to the user community to help parse and interpret this layer.

In addition to data access and transformation processes, AppEEARS also has the capability to unpack and interpret the quality layer.

The QA bit flags for the QC_250m_1 layer is provided in Table 8 of the User Guide on page 19.

Known Issues

Striping due to a dead detector is noticeable for bands 5, 6, and 7 in scenes acquired February 24 through October 31, 2000. Corrections were implemented to reduce the striping in data acquired after November 1, 2000. Users should always check the band quality for dead detectors even though reflectance values may be in the valid range. For complete information about the MOD09GQ known issues please refer to the MODIS Land Quality Assessment website.

Documentation

Using the Data

E-Learning

Getting Started with MODIS V6 Surface Reflectance Data Part 3: Interpreting Quality Information

Data In Action

Highlights from the Literature: April to June 2016

The NASA DEVELOP National Program Spring/Summer 2014

Decembrrrr: Observing Sea Ice Using MODIS Data

Highlights from the Literature: April to June 2019

Tools

Citation

DOI: 10.5067/MODIS/MOD09GQ.006

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