Algorithm Theoretical Basis Document (ATBD)
The MYD17A3H Version 6 product provides information about annual Net Primary Production (NPP) at 500 meter (m) pixel resolution. Annual NPP is derived from the sum of all 8-day Net Photosynthesis (PSN) products (MYD17A2H) from the given year. The PSN value is the difference of the Gross Primary Productivity (GPP) and the Maintenance Respiration (MR).
Validation at stage 3 has been achieved for the MODIS Gross and Net Primary Productivity data products. Further details regarding MODIS land product validation for the MYD17 data products are available from the MODIS Land Team Validation site.
|File Size||~0.79 MB|
|Temporal Extent||2002-12-27 to 2004-01-03|
|Geographic Dimensions||1200 km x 1200 km|
|Number of Science Dataset (SDS) Layers||2|
|Columns/Rows||2400 x 2400|
|Pixel Size||500 m|
|SDS Name||Description||Units||Data Type||Fill Value||No Data Value||Valid Range||Scale Factor|
|Npp_500m||Net Primary Productivity||kg C/m²||16-bit signed integer||32767||N/A||-30000 to 32700||0.0001|
|Npp_QC_500m||Quality Control Bits||Bit Field||8-bit unsigned integer||255||N/A||0 to 254||N/A|
|32761||Land cover assigned as "unclassified" or not able to determine|
|32762||Land cover assigned as urban/built-up|
|32763||Land cover assigned as "permanent" wetlands/inundated marshland|
|32764||Land cover assigned as perennial snow, ice|
|32765||Land cover assigned as barren, sparse veg (rock, tundra, desert)|
|32766||Land cover assigned as perennial salt or inland fresh water|
The bit flags for the Npp_QC_500m Quality layer are provided in the MYD17A3H File Specification.
The 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 this layer.
In addition to data access and transformation processes, AppEEARS also has the capability to unpack and interpret the quality layer.
For complete information about the MYD17A3H known issues refer to the MODIS Land Quality Assessment website.