Aqua MODIS NDVI data from the MYD13C2 product across the globe, July 2018.View full-size image
The MYD13C2 Version 6 product provides a Vegetation Index (VI) value at a per pixel basis. There are two primary vegetation layers. The first is the Normalized Difference Vegetation Index (NDVI) which is referred to as the continuity index to the existing National Oceanic and Atmospheric Administration-Advanced Very High Resolution Radiometer (NOAA-AVHRR) derived NDVI. The second vegetation layer is the Enhanced Vegetation Index (EVI), which has improved sensitivity over high biomass regions.
The Climate Modeling Grid (CMG) consists of 3,600 rows and 7,200 columns of 5,600 meter (m) pixels. In generating this monthly product, the algorithm ingests all the MYD13A2 products that overlap the month and employs a weighted temporal average. Global MYD13C1 data are cloud-free spatial composites and are provided as a Level 3 product projected on a 0.05 degree (5,600 m) geographic CMG. The MYD13C2 has data fields for the NDVI, EVI, VI QA, reflectance data, angular information, and spatial statistics such as mean, standard deviation, and number of used input pixels at the 0.05 degree CMG resolution.
|File Size||~99 MB|
|Temporal Extent||2002-07-01 to Present|
|Coordinate System||Geographic Latitude and Longitude|
|Number of Science Dataset (SDS) Layers||13|
|Columns/Rows||7200 x 3600|
|Pixel Size||5600 m|
|SDS Name||Description||Units||Data Type||Fill Value||No Data Value||Valid Range||Scale Factor|
|CMG 0.05 Deg Monthly NDVI||16 day NDVI||NDVI||16-bit signed integer||-3000||N/A||-2000 to 10000||0.0001|
|CMG 0.05 Deg Monthly EVI||16 day EVI||EVI||16-bit signed integer||-3000||N/A||-2000 to 10000||0.0001|
|CMG 0.05 Deg Monthly VI Quality||VI quality indicators||Bit Field||16-bit unsigned integer||65535||N/A||0 to 65534||N/A|
|CMG 0.05 Deg Monthly red reflectance||Surface Reflectance Band 1||N/A||16-bit signed integer||-1000||N/A||0 to 10000||0.0001|
|CMG 0.05 Deg Monthly NIR reflectance||Surface Reflectance Band 2||N/A||16-bit signed integer||-1000||N/A||0 to 10000||0.0001|
|CMG 0.05 Deg Monthly blue reflectance||Surface Reflectance Band 3||N/A||16-bit signed integer||-1000||N/A||0 to 10000||0.0001|
|CMG 0.05 Deg Monthly MIR reflectance||Surface Reflectance Band 7||N/A||16-bit signed integer||-1000||N/A||0 to 10000||0.0001|
|CMG 0.05 Deg Monthly Avg sun zen angle||Sun zenith angle of VI Pixel||Degree||16-bit signed integer||-10000||N/A||-9000 to 9000||0.01|
|CMG 0.05 Deg Monthly NDVI std dev||Standard deviation computed from input NDVI pixels||NDVI||16-bit signed integer||-3000||N/A||0 to 10000||0.0001|
|CMG 0.05 Deg Monthly EVI std dev||Standard deviation computed from input EVI pixels||EVI||16-bit signed integer||-3000||N/A||0 to 10000||0.0001|
|CMG 0.05 Deg Monthly #1km pix used||Number of 1 km input pixels used||Number||8-bit unsigned integer||255||N/A||0 to 36||N/A|
|CMG 0.05 Deg Monthly #1km pix +-30deg VZ||Number of 1km pixels used with VZ angle less than + or - 30 degs||Number||8-bit unsigned integer||255||N/A||0 to 36||N/A|
|CMG 0.05 Deg Monthly pixel reliabilty||Quality reliability of VI pixel||Rank||8-bit signed integer||-1||N/A||0 to 4||N/A|
The QA bit flags for the "CMG 0.05 Deg Monthly pixel reliabilty" layer are provided in Table 18 on page 27 and the "CMG 0.05 Deg Monthly VI Quality" layer in Table 5 on page 16 of the User Guide.
Quality assurance information should be considered when determining the usability of data for a particular science application. The ArcGIS MODIS-VIIRS Python Toolbox contains tools capable of decoding quality data layers while producing thematic quality raster files for each quality attribute.
The "CMG 0.05 Deg Monthly VI Quality" 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 the quality layer.
The incorrect representation of the aerosol quantities (low, average, high) in the Collection 6 MYD09 surface reflectance products may have impacted MYD13 Vegetation Index data products particularly over arid bright surfaces.
Corrections will be implemented in Collection 6.1 reprocessing in 2020.
For complete information about the MYD13C2 known issues please refer to the MODIS Land Quality Assessment website.