## NASA Level-3 Data Product Reader

### Ocean Level-3 Binned Data Products

Level-3 binned data products consist of the accumulated data for all Level-2 data corresponding to a period of one day, 8 days, a calendar month, or a calendar year. Each Level-3 binned data product is stored in one or more HDF files. Each multi-file product includes a main file containing all product-level metadata and data for each bin that are common to all the binned geophysical parameters, and multiple subordinate files, each of which contains data of one binned geophysical parameter for all bins. Subordinate files must be read in conjunction with the associated main file.

Format Specifications:

- SeaWiFS Level 3 Binned Products Document
  https://oceancolor.gsfc.nasa.gov/PRODUCTS/binned.html
- MODIS Level 3 Binned Products Document
  https://oceancolor.gsfc.nasa.gov/PRODUCTS/modis_binned.html
- Ocean Level-3 Data Binned Products Document
  https://oceancolor.gsfc.nasa.gov/DOCS/Ocean_Level-3_Binned_Data_Products.pdf

### Ocean Level-3 Standard Mapped Image Products

The Level-3 standard mapped image (SMI) products are image representations of binned data products generated from SeaWiFS, MODIS, OCTS or CZCS data. The data in each SMI product represents an image of the parameter specified by the global attribute Parameter. This object is a two-dimensional array of an Equidistant Cylindrical (also known as Platte Carre) projection of the globe. The values can be stored as bytes, 2-byte integers, or 4- byte floats. The first two are scaled real values and may be converted projected to geophysical values using the global attributes Scaling, Scaling Equation, Base, Slope, and Intercept. Actual SMI files can be downloaded from our level-3 browser. The standard SMI products are generated from binned data products, one for each of the following geophysical parameters: chlorophyll a concentration, angstrom coefficient, normalized water-leaving radiance at each visible wavelength, aerosol optical thickness, epsilon, and diffuse attenuation coefficient at 490 nm. For MODIS, products are generated for sea surface temperature (SST), 4 micron SST (SST4) and nighttime SST (NSST). Thus, each SMI product represents data binned over the period covered by the parent product. The arithmetic mean is used in each case to obtain the values for the SMI grid points from the binned data products. Each SMI product contains one image of a geophysical parameter and is stored in one physical HDF file.

Format Specifications

- Ocean Level-3 SMI Data Products Document
  https://oceancolor.gsfc.nasa.gov/DOCS/Ocean_Level-3_SMI_Products.pdf