{"id":"da183c26-4ab2-47a5-b580-54f72539cee6","task":"Transform a hydrographic survey's ellipsoidal heights into a local tidal datum (e.g., Mean Lower Low Water) for a waterfront boundary determination.","domain":"vdatum.noaa.gov","steps":["Review VDatum API documentation at https://vdatum.noaa.gov/docs/services.html (current release VDatum 4.8).","Call the REST conversion endpoint at https://vdatum.noaa.gov/vdatumweb/api/convert with source/target datum codes and point coordinates.","For coastal/tidal work specifically, use the VDatum Tidal API variant to go from ellipsoidal or orthometric heights to tidal datums (MLLW, MHW, etc.).","Validate output against the interactive web tool at vdatum.noaa.gov/vdatumweb/ for a handful of spot-check points before trusting a batch run.","Confirm regional coverage — VDatum's tidal transformation grids are not uniform nationwide and gaps exist in some inland/estuarine zones."],"gotchas":["VDatum is a distinct NOAA product line from NCAT/NGS geodetic tools even though it's developed jointly by NGS, Office of Coast Survey, and CO-OPS — don't assume NCAT's datum list covers tidal datums.","Results are returned in JSON but the API is versioned to the desktop VDatum release; a locally installed older VDatum version can disagree with the live web API by design."],"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":"sampled","url":"https://mcp.waymark.network/r/da183c26-4ab2-47a5-b580-54f72539cee6"}