NCSS Soil Characterization Database / Lab Data Mart¶
| Field | Current catalog entry |
|---|---|
| Provider | NCSS Soil Characterization Database, often called Lab Data Mart or KSSL data |
| Organization | USDA-NRCS National Soil Survey Center / Kellogg Soil Survey Laboratory and partners |
| Coverage | U.S. pedons with additional contributed records; spatial density is uneven |
| Data type | Observed laboratory and field characterization by pedon and horizon |
| Properties | Physical, chemical, mineralogical, taxonomic, and method metadata; availability varies by sample |
| Spatial resolution | Point pedons; coordinates and disclosure precision vary |
| Depths | Sampled horizons with variable boundaries |
| Access | Laboratory tables through USDA Soil Data Access; whole-database SQLite/GeoPackage downloads and separate companion morphology downloads |
| Authentication | None for the public SDA query service used by OpenSoil |
| Rate limits | No stable public quota assumed; OpenSoil applies bounded queries, rate limits, timeouts, retries, and a timestamped cache |
| License and citation | No explicit dataset license has been encoded; cite the NCSS Soil Characterization Database and retain provider terms |
| OpenSoil status | experimental |
Why it is different¶
These are measured characterization records, not representative map-unit values. They can answer questions that SSURGO cannot, but require careful treatment of analytical method, censored values, sampled depth, date, coordinate precision, and contributor-specific terms.
OpenSoil does not join a nearby pedon to a field or imply that it represents a search area. The experimental adapter provides:
- bounded GeoJSON discovery through
GET /v1/pedons; - method-rich horizon observations through
GET /v1/pedons/{pedon_key}; - the corresponding SDA lab table through the raw provider route;
- pedon, site, layer, and laboratory sample identifiers;
- original reported strings, analytical method codes, units, and depths;
- explicit handling for less-than and greater-than reporting limits;
- cache timestamps and warnings about coordinate accuracy, completeness, and representativeness.
Selected interface and schema boundary¶
USDA states that NCSS laboratory tables are accessible through SDA, while companion morphological pedon data are not available through that service. Version 0.2 uses only fixed-shape, server-authored queries against lab_combine_nasis_ncss, lab_pedon, lab_layer, lab_physical_properties, lab_chemical_properties, and lab_area. Callers cannot submit SQL.
The adapter intentionally does not ingest or silently join the separately distributed companion morphological database. That boundary is visible in every detail response. Preparation rows prefer the provider's S preparation when available, and no unit conversion or inferred method is applied.
The canonical fields currently mapped are pH in water, Walkley-Black organic carbon, particle-size sand/silt/clay, one-third-bar bulk density, ammonium-acetate CEC at pH 7, total nitrogen by NCS, and saturated-paste electrical conductivity. These are method-specific mappings, not assertions that other methods are interchangeable.
Coordinate and use limitations¶
USDA warns that older locations may have been approximated from aerial photographs or assigned a least-arbitrary coordinate. The public lab-table response does not provide a reliable numeric horizontal-accuracy value per record, so OpenSoil returns null rather than inventing one.
The provider also warns that analytical coverage is often incomplete, some retained measurements can be misleading or outside a method's best applicability range, and users are responsible for assessing fitness. A missing property does not mean the property was absent.
Official NCSS Soil Characterization Data page · Official data-use and citation guidance · Official database access