MYD09GA v006

MODIS/Aqua Surface Reflectance Daily L2G Global 1 km and 500 m SIN Grid


PI: Eric Vermote

Description

The MYD09GA Version 6 product provides an estimate of the surface spectral reflectance of Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) Bands 1 through 7, corrected for atmospheric conditions such as gasses, aerosols, and Rayleigh scattering. Provided along with the 500 meter (m) surface reflectance, observation, and quality bands are a set of ten 1 km observation bands and geolocation flags. The reflectance layers from the MYD09GA are used as the source data for many of the MODIS land products.

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 provide 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 MYD09GA data product is available from the MODIS land team validation site.

Collection and Granule

Collection

Characteristic Description
CollectionAqua MODIS
DOI10.5067/MODIS/MYD09GA.006
File Size84 MB
Temporal ResolutionDaily
Temporal Extent2002-07-04 to Present
Spatial ExtentGlobal
Coordinate SystemSinusoidal
DatumN/A
File FormatHDF
Geographic Dimensions1200 km x 1200 km

Granule

Characteristic Description
Number of Science Dataset (SDS) Layers22
Columns/Rows2400 x 2400 (500 m) and 1200 x 1200 (1000 m)
Pixel Size500 m and 1000 m

Layers

SDS Name Description Units Data Type Fill Value No Data Value Valid Range Scale Factor Additional Offset
num_observations_1km Number of observations within a  pixel N/A 8-bit signed integer -1 N/A 0 to 127 N/A N/A
state_1km_1 1km Reflectance Data State QA Bit Field 16-bit unsigned integer 65535 N/A 0 to 57335 N/A N/A
SensorZenith_1 Zenith angle to sensor Degree 16-bit signed integer -32767 N/A 0 to 18000 0.01 N/A
SensorAzimuth_1 Azimuth angle to sensor Degree 16-bit signed integer -32767 N/A -18000 to 18000 0.01 N/A
Range_1 Distance to sensor Meters 16-bit unsigned integer 0 N/A 27000 to 65535 0.04 N/A
SolarZenith_1 Zenith angle to sun Degree 16-bit signed integer -32767 N/A 0 to 18000 0.01 N/A
SolarAzimuth_1 Azimuth angle to sun Degree 16-bit signed integer -32767 N/A -18000 to 18000 0.01 N/A
gflags_1 Geolocation flags Bit Field 8-bit unsigned integer 255 N/A 0 to 248 N/A N/A
orbit_pnt_1 Orbit pointer N/A 8-bit signed integer -1 N/A 0 to 15 N/A N/A
granule_pnt _1 Granule pointer N/A 8-bit unsigned integer 255 N/A 0 to 254 N/A N/A
num_observations_500m Number of observations per 500m pixel N/A 8-bit signed integer -1 N/A 0 to 127 N/A N/A
sur_refl_b01_1¹ Surface Reflectance Band 1 N/A 16-bit signed integer -28672 N/A -100 to 16000 0.0001 N/A
sur_refl_b02_1¹ Surface Reflectance Band 2 N/A 16-bit signed integer -28672 N/A -100 to 16000 0.0001 N/A
sur_refl_b03_1 Surface Reflectance Band 3 N/A 16-bit signed integer -28672 N/A -100 to 16000 0.0001 N/A
sur_refl_b04_1 Surface Reflectance Band 4 N/A 16-bit signed integer -28672 N/A -100 to 16000 0.0001 N/A
sur_refl_b05_1 Surface Reflectance Band 5 N/A 16-bit signed integer -28672 N/A -100 to 16000 0.0001 N/A
sur_refl_b06_1 Surface Reflectance Band 6 N/A 16-bit signed integer -28672 N/A -100 to 16000 0.0001 N/A
sur_refl_b07_1 Surface Reflectance Band 7 N/A 16-bit signed integer -28672 N/A -100 to 16000 0.0001 N/A
QC_500m_1 Surface Reflectance 500m Quality Assurance Bit Field 32-bit unsigned integer 787410671 N/A 0 to 4294966019 N/A N/A
obscov_500m_1 Observation coverage Percent 8-bit signed integer -1 N/A 0 to 100 0.01 N/A
iobs_res_1 Observation number N/A 8-bit unsigned integer 255 N/A 0 to 254 N/A N/A
q_scan_1² 250m scan value information N/A 8-bit unsigned integer 255 N/A 0 to 254 N/A N/A

¹Data layers sur_refl_b01_1 and sur_refl_b02_1 may not always be present.

²Description information for the q_scan_1 layer is provided in Table 17 of the User Guide. Please note this layer may not be present in all products.

Product Quality

The state_1km_1 and QC_500m_1 layers are 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 these layers.

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

The QA bit flags for the state_1km_1 and the QC_500m_1 layers are given in the User Guide in table 13 and 10 respectively.

Known Issues

For complete information about the MYD09GA 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

Decades of Dormancy: Calbuco Awakens

The Chandeleur Barrier Islands: Hurricane Katrina 10 Years Later

Using MODIS Fire Products to observe Australian Bushfires

Sensing Our Planet: NASA Earth Science Research Features 2015

Hurricane Ivan: 10 Years Later

Flooding of the Shire River

Tools

Citation

DOI: 10.5067/MODIS/MYD09GA.006

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