GroundLayers
TRANSPARENCY & METHODOLOGY

How GroundLayers Uses Public Data

How address inputs are matched to geographic coordinates, how public government datasets are assembled, and how technical limitations are handled.

1. Overview of the Lookup Pipeline

When you enter an address into GroundLayers, the system converts that text into verified geographic coordinates, dispatches simultaneous queries to official federal endpoints, and compiles the returned public records into an accessible report.

GroundLayers operates as an independent reader of public records. We do not maintain private databases of soil samples or elevation measurements; every record reflects published data from U.S. federal agencies.

2. Address Matching & Geocoding

Plain-Language Summary: Computers cannot query spatial datasets using street names directly. An address must first be translated into an exact latitude and longitude on the Earth's surface.

Technical Implementation: GroundLayers submits structured address components (Street, City, State, ZIP) over HTTPS to the official U.S. Census Bureau Geocoding Services REST API using the Public_AR_Current benchmark. The Census geocoder references TIGER/Line street centerline databases and returns WGS84 coordinates (latitude/longitude), along with matching metadata.

Limitation: Street centerline geocoding estimates location along a street segment. It represents an approximate coordinate point rather than surveyed property boundary corners.

3. Parallel Public Dataset Assembly

Plain-Language Explanation: Rather than waiting for one agency server to respond before asking the next, GroundLayers queries each federal provider at the same time.

Technical Implementation: Using server-side Promise.allSettled, GroundLayers queries independent REST, WMS, and WQL services simultaneously:

  • NLCD 2021 Land Cover (MRLC / USGS): Spatial point query to GeoServer returning 30-meter satellite surface classification.
  • USDA SSURGO Soils (USDA NRCS): Spatial query via Soil Data Access (SDA) REST API returning map unit symbols, component series, drainage classes, and hydrologic runoff groups.
  • USGS 3DEP Elevation (USGS): 3D Elevation Program point elevation query returning ground height above sea level in feet and meters.
  • USGS Watersheds (USGS WBD): Spatial query to Hydro MapServer Layer 6 identifying local 12-digit HUC-12 subwatershed boundaries.
  • FEMA Flood Hazards (FEMA NFHL): Spatial query to Layer 28 of the National Flood Hazard Layer returning official Special Flood Hazard Area designations where active.
  • USGS Seismic Catalog (USGS ANSS): FDSN event query recording historical earthquake counts within 100 km (pure factual catalog records, not predictive risk scores).

4. Soil Data & Classification Methodology

Plain-Language Explanation: Soil information comes from decades of field surveys conducted by USDA soil scientists. A soil “map unit” is a designated geographic area where specific soil types are commonly found together.

Key Metrics Defined:

  • Map Unit Name: The official USDA designation (e.g. Sharkey clay, 0 to 1 percent slopes), identifying the dominant soil association.
  • Drainage Class: Natural wetness conditions of the soil under natural vegetation (e.g. Well drained, Moderately well drained, Poorly drained).
  • Hydrologic Soil Group: Runoff potential classification (Group A has high infiltration and low runoff; Group D has low infiltration and high runoff).
  • County Soil Summaries: County reference pages are produced by calculating true vector spatial intersections between U.S. Census county land boundaries and USDA SSURGO map unit polygons in EPSG:5070 equal-area projection.

5. Partial Result Isolation & Zero Guesswork

Federal agency endpoints occasionally experience maintenance downtime, network timeouts, or service interruptions. GroundLayers isolates each provider inside an independent error boundary.

Strict Non-Inference Rule: If an upstream agency service times out or fails to respond, GroundLayers explicitly labels that section as Unavailable (Upstream Service Timeout). We never guess, never assume “low risk”, and never fabricate fallback values like default flood zones.

6. Caching & Respect for Public Infrastructure

To avoid placing repetitive strain on public government APIs and to deliver fast responses, successful responses are cached in server memory using normalized coordinate keys. Caches expire automatically and never store personal user data.

7. What GroundLayers Is Not

To avoid confusion and misuse of public data, it is critical to understand the boundaries of this utility:

  • Not a Certified Land Survey: We do not verify property pins, fences, or legal boundaries. Coordinates are street centerline estimates.
  • Not a Structural Engineering Report: Soil classifications and slope percentages describe regional characteristics, not onsite foundation bearing capacity or soil compaction.
  • Not a Phase I Environmental Site Assessment: GroundLayers does not assess hazardous waste contamination, underground storage tanks, or historical chemical releases.
  • Not a Flood Insurance Determination: Official flood zone designations for insurance or mortgage requirements require a certified Letter of Map Amendment (LOMA) or formal elevation certificate.