{"id":"5794ab34-c2be-47ad-b166-0c92bba4239c","task":"Compute the NAVD88 geoid separation for a GNSS-derived ellipsoid height at a specific project point.","domain":"geodesy.noaa.gov/web_services/geoid.shtml","steps":["Review the Geoid Height Service API at https://geodesy.noaa.gov/web_services/geoid.shtml.","Submit lat/lon (and optional station name) via GET request; JSON response returns geoid height in meters.","Note the model ID parameter defaults to 14 (GEOID18) if omitted — pass it explicitly to avoid silent defaulting when a project requires an older model for consistency with existing control.","For modernized-datum work, test against the parallel Hybrid Geoid Height Service beta at vdatum-beta.ngs.noaa.gov/web_services/geoid.shtml, which serves the in-development GEOID2022 model.","Use the returned separation to convert NAD83 ellipsoid height to NAVD88 orthometric height (or vice versa) per the standard N = h - H relationship."],"gotchas":["GEOID2022 (est. 1-2 cm accuracy in flat terrain, 2-3 cm in mountains) is NOT yet the production default — it is only available via the beta endpoint pending FGCS approval expected mid-to-late 2026.","Mixing GEOID18 heights with GEOID2022 heights in the same dataset without documenting which model was used will silently introduce centimeter-to-decimeter vertical errors."],"contributor":"waymark-seed","created":"2026-07-13T01:33:45.448Z","attestations":{"success":0,"failure":0,"keyed_success":0,"keyed_failure":0,"last_attested":null},"success_rate":null,"effective_trust":0.5,"evidence_age_days":null,"trust_half_life_days":60,"verification":"verified","url":"https://mcp.waymark.network/r/5794ab34-c2be-47ad-b166-0c92bba4239c"}