Glossary¶
- API
- Application Programming Interface — a set of protocols and tools for programmatic access to data and services.
- ATBD
- Algorithm Theoretical Baseline Document — a document describing the scientific basis and methodology of a data product.
- CCI
- Climate Change Initiative — an ESA programme that generates long-term satellite-derived climate data records.
- Copernicus
- The European Union’s Earth observation programme, which provides free and open satellite data through missions such as Sentinel-1.
- CRS
- Coordinate Reference System — a system that defines how geographic coordinates relate to locations on the Earth’s surface. All Spire soil moisture products use WGS 84 (EPSG:4326).
- CSV
- Comma-Separated Values — a plain-text tabular data format.
- CYGNSS
- Cyclone Global Navigation Satellite System — a NASA constellation of eight small satellites that measure ocean surface winds and soil moisture using GNSS-R at L-band, covering 38°N–38°S.
- DDM
- Delay-Doppler Map — a two-dimensional representation of reflected GNSS signals used in GNSS-R processing.
- DEM
- Digital Elevation Model — a gridded representation of terrain elevation.
- EPSG
- European Petroleum Survey Group geodetic parameter dataset code used to identify coordinate reference systems (for example, EPSG:4326 for WGS 84).
- D-ESSM
- Daily Enhanced Surface Soil Moisture — the 500 m resolution soil moisture product, produced by downscaling D-MSSM using Sentinel-1 SAR data.
- D-HSSM
- Daily High-resolution Surface Soil Moisture — the 100 m resolution soil moisture product, produced by downscaling D-MSSM using Sentinel-1 SAR data. Available for custom regions only.
- D-MSSM
- Daily Medium-resolution Gap-filled Surface Soil Moisture — the 6 km resolution soil moisture product, derived from multi-sensor fusion (SMAP, CYGNSS, Spire GNSS-R, and SMOS) with machine-learning gap-filling.
- ESA
- European Space Agency.
- ESSM
- Enhanced Surface Soil Moisture — see D-ESSM.
- FC
- Forecast — a forward-looking product variant driven by the SOF-D weather model.
- GeoJSON
- A JSON-based format for encoding geographic features, their geometry, and associated properties.
- GeoTIFF
- Georeferenced Tag Image File Format — a raster image format with embedded geospatial metadata.
- GLONASS
- Global Navigation Satellite System (Russia) — one of the satellite navigation systems used in GNSS-R observations.
- GNSS
- Global Navigation Satellite System — the general term for satellite navigation systems (e.g., GPS, Galileo, GLONASS, BeiDou, QZSS).
- GNSS-R
- Global Navigation Satellite System – Reflectometry — a remote sensing technique that measures GNSS signals reflected from the Earth’s surface to infer surface properties such as soil moisture.
- GPS
- Global Positioning System — the United States satellite navigation system, one of several GNSS constellations.
- GRD
- Ground Range Detected — a SAR image product in which pixel values represent radar backscatter projected onto the ground plane. Used in Sentinel-1 data processing.
- HSSM
- High-resolution Surface Soil Moisture — see D-HSSM.
- LEO
- Low Earth Orbit — an orbit at altitudes below approximately 2,000 km, used by many Earth observation satellites.
- MSSM
- Medium-resolution Surface Soil Moisture — see D-MSSM.
- NASA
- National Aeronautics and Space Administration.
- NetCDF4
- Network Common Data Form version 4 — a self-describing file format commonly used for scientific geospatial and time-series data.
- NRT
- Near-Real-Time — a product tier with approximately one-day latency, providing early delivery of data that is later superseded by the standard product.
- SAR
- Synthetic Aperture Radar — a radar imaging technique that produces high-resolution images by combining multiple radar pulses.
- Sentinel-1
- An ESA Copernicus C-band SAR satellite mission providing radar imagery used in Spire’s downscaling methodology to produce D-ESSM and D-HSSM products.
- SM
- Soil Moisture — the volumetric water content of soil, expressed in m³/m³.
- SMAP
- Soil Moisture Active Passive — a NASA satellite mission launched in 2015 that measures global soil moisture using an L-band radiometer.
- SMOS
- Soil Moisture and Ocean Salinity — an ESA satellite mission launched in 2009 that measures surface soil moisture using an L-band radiometer.
- SOF-D
- Spire Operational Forecast – Deterministic — Spire’s global weather forecast model that drives the soil moisture forecast products. It runs four times daily at 00, 06, 12, and 18 UTC.
- SSM
- Surface Soil Moisture — the water content of the top few centimetres of soil.
- TRI
- Terrain Ruggedness Index — a measure of terrain variability derived from elevation data, used in quality flagging for D-ESSM and D-HSSM.
- USCRN
- U.S. Climate Reference Network — a network of climate monitoring stations operated by NOAA across the United States, used for validation of soil moisture products.
- UTC
- Coordinated Universal Time — the primary time standard used for all product timestamps.
- WGS
- World Geodetic System — a global reference frame for geodesy and navigation. All Spire soil moisture products use WGS 84 (EPSG:4326).
- WKT
- Well-Known Text — a text format for representing spatial reference systems and geometries.