Soil Moisture Active Passive Data (SMAP)
To review the processing and algorithm history for all versions of SMAP data sets, download the following workbooks which get updated on a periodic basis.
Explaining SMAP Version IDs
Composite Release IDs (CRIDs)
SMAP Level-1 through Level-3 data file names include a Composite Release ID (CRID) that represents changes to any data processing condition that might impact SMAP products. The CRID incorporates algorithm, software, and other parameters involved in data processing. Note: The major version does not necessarily coincide with the CRID major version.
Files are named according to the following convention, with the CRID shown in bold:
SMAP_L1A_RADIOMETER_[Orbit#]_[A/D]_yyyymmddThhmmss_RLVvvv_NNN.[ext]
Where:
| Variable | Description |
|---|---|
| R | Release |
| L | Launch Indicator (1: SMAP Standard Data) |
| V | 1-Digit CRID Major Version Number |
| vvv | 3-Digit CRID Minor Version Number |
Science Version IDs
SMAP Level-4 data file names include a Science Version ID that, like the Composite Release ID for Level-1 through -3 data, represents changes to any data processing condition that might impact SMAP product results.
Files are named similar to the following convention, with the Science Version ID shown in bold:
SMAP_L4_C_MDL_yyyymmddThhmmss_VLMmmm_NNN.[ext]
Where:
| Variable | Description |
|---|---|
| V | Science Version |
| L | Launch Indicator (b: Beta-quality data, v: Validated data) |
| M | 1-Digit Major Science Version Number |
| mmm | 3-Digit Minor Science Version Number |
Maturity States
There are two categories for all SMAP products:
- Beta — Indicates data sets using a developing algorithm with updates anticipated.
- Validated — Data sets are upgraded to Validated once the Beta algorithm is verified by the algorithm team and validated by the validation team.
Validation Stages
A stage (1, 2, 3, or 4) may be appended to Validated product maturity codes. The following table that describes the validation stages is based on the guidance provided by the CEOS (2015), Committee on Earth Observation Satellites (CEOS) Working Group on Calibration and Validation (WGCV), the CEOS WGCV Land Products Sub-Group, and can be summarized as follows (Colliander et al. 2021, Appendix A).
| Validation Stage | Description |
|---|---|
| Stage 1 | Product accuracy is assessed from a small (typically < 30) set of locations and time periods by comparison with in-situ or other suitable reference data. |
| Stage 2 | Product accuracy is estimated over a significant (typically > 30) set of locations and time periods by comparison with reference in situ or other suitable reference data. Spatial and temporal consistency of the product, and its consistency with similar products, has been evaluated over globally representative locations and time periods. Results are published in the peer-reviewed literature. |
| Stage 3 | Uncertainties in the product and its associated structure are well quantified over a significant (typically > 30) set of locations and time periods representing global conditions by comparison with reference in situ or other suitable reference data. Validation procedures follow community-agreed-upon good practices. Spatial and temporal consistency of the product, and its consistency with similar products, has been evaluated over globally representative locations and time periods. Results are published in the peer-reviewed literature. |
| Stage 4 | Validation results for Stage 3 are systematically updated when new product versions are released and as the interannual time-series expands. When appropriate for the product, uncertainties in the product are quantified using fiducial reference measurements over a global network of sites and time periods (if available). |