NYC Boundaries — Technical Data

One city, several valid boundaries

A boundary depends on the question being asked. The Department of City Planning publishes both water-excluded shoreline geometry and water-included geometry. The Census Bureau publishes county land and water measurements. OpenStreetMap represents each borough and its corresponding county as separate administrative relations, even where they refer to the same real-world extent. geoBoundaries republishes generalized, shoreline-clipped Census-derived county geometry; Overture Maps integrates the exact OpenStreetMap relation versions already governed here while adding stable division and area identifiers. Who's On First adds stable gazetteer identifiers, hierarchy and concordances for the five counties; its default county geometry is a Census-sourced Quattroshapes derivative.

These are not interchangeable records. This view keeps the source, method, administrative framing and review assessment attached to each claim.

Compared views

Confidence values qualify the reviewed mappings or assertions in this collection; they are not universal ratings of an entire publisher or dataset. Source update values come from each publisher’s own dataset, distribution or version metadata; retrieval, review and publication times are recorded separately. Derived representations remain in their upstream provenance cluster and are not counted as independent corroboration.

Provenance clusters

Representation count is not evidence count. A downstream product can add useful identifiers, release history or geometry semantics while still inheriting its boundary claim from an upstream source.

The confidence score for geoBoundaries qualifies the reviewed cross-release identity mapping. The Overture score qualifies mappings to exact OSM relation versions. The Who's On First score qualifies mappings supported by exact Census GEOID concordances. None is a claim of independent authority.

Where independent land-area measurements agree

The two independent, directly comparable land-area series are within 1.25% for every borough/county pair; this is treated as ordinary cross-source measurement variance, not a contradiction.

Differences that should remain visible

Published fixture and artifacts

The DCP water-excluded and water-included geometries, five Census Gazetteer county measurement records, ten exact OpenStreetMap relation-version metadata records, five geoBoundaries county geometries, five Who's On First county geometries, and eleven Overture Maps division-area geometries are downloadable public fixtures. The comparison map overlays the DCP geometries without a network request. The OpenStreetMap export contains metadata only—not geometry, relation members, Nominatim bounds, centroids, or numeric area. The geoBoundaries export contains the retained generalized, shoreline-clipped 2018 Census-derived geometries with CC BY 4.0 attribution and no numeric area. The Who's On First export contains the retained current Quattroshapes-derived county geometries with stable WOF identifiers, Census GEOID/HASC concordances, and a Shapely-derived geom:area_square_m field disclosed as non-independent. The Overture export contains eleven division-area geometries re-verified directly against the pinned release at publication time, including both of Richmond County's land and maritime representations, with ODbL attribution and no numeric area.

• Water-excluded fixtureJSON · five preprojected borough paths
• Water-included fixtureJSON · five GeoJSON MultiPolygons
• Census Gazetteer measurementsJSON · five county records; ALAND, AWATER and internal points; no geometry
• OpenStreetMap relation metadataJSON · ten exact county/borough relation versions; metadata only; no geometry
• geoBoundaries county geometryGeoJSON · five generalized, shoreline-clipped 2018 county representations · CC BY 4.0
• Who's On First county geometryGeoJSON · five current Quattroshapes-derived county representations · CC BY (Quattroshapes) / CC0 (WOF structure)
• Overture Maps division-area geometryGeoJSON · eleven representations including Richmond County land and maritime areas · ODbL 1.0
• Retained source responseGeoJSON · exact DCP API snapshot
• Boundary overlaySVG · water included and excluded
• Shoreline mapSVG · water excluded only
• Fixture builderPython · retained response to public fixture
• Map generatorPython · no network dependency
• Checksum manifestSHA-256 verification
• Structured descriptionJSON-LD

Validation and provenance

Source last-updated values are now backed by primary publisher metadata: Socrata data-update timestamps for DCP, the HTTP Last-Modified value for the Census distribution, and exact OpenStreetMap relation versions. The retained DCP water-included response was captured on August 9, 2026; capture, source update, review and publication remain distinct events.

• Both public fixtures require exactly five unique borough identities and non-empty geometries.
• The retained water-included API response regenerates the public fixture byte for byte.
• Both SVGs regenerate byte for byte from public fixtures without a network request.
• The source snapshot, fixtures, builders, generators and SVGs are covered by SHA-256 checksums.
• The retained geoBoundaries subset regenerates as a schema-valid five-feature fixture with byte-identical geometry coordinates, deterministic borough ordering, attribution and limitations.
• The retained Who's On First subset regenerates as a schema-valid five-feature fixture with byte-identical Quattroshapes geometry coordinates, deterministic borough ordering, Census GEOID/HASC concordances and a disclosed non-independent geom:area_square_m field.
• The Overture subset regenerates as a schema-valid eleven-feature fixture with byte-identical geometry re-queried directly from the pinned release, exactly one land and one maritime representation for Richmond County, and deterministic borough ordering.
• The source comparison now covers 46 active governed records: 10 DCP, 5 Census Gazetteer, 10 OpenStreetMap, 5 geoBoundaries, 11 Overture and 5 Who's On First representations.
• geoBoundaries and Who's On First remain in the Census provenance cluster, and Overture remains in the OpenStreetMap provenance cluster; none increases the independent-source count.
• The source comparison contains no recorded contradiction: observed differences are assessed as methodological choices, administrative framing or ordinary measurement variance.
• KnoEdg.NYC publishes this view; each claim continues to identify its applicable public evidence source.

Known limitations

The original DCP API response used for the first map was not retained with a checksum, and the initial geographic-to-SVG projection script was not preserved. Reproducibility therefore begins with the reviewed public SVG-path fixture, not the original API response. Future boundary publications are required to retain the complete response and transformation chain before first publication.

The water-included publication corrects that practice prospectively: its exact API response, checksum, normalized fixture, fixed projection and generated overlay are retained. The Census records are published as measurements without geometry. The OpenStreetMap records are published as exact relation-version metadata without geometry, relation members, Nominatim bounds, centroids, or numeric area. The geoBoundaries publication contains retained generalized, shoreline-clipped 2018 Census-derived geometry with no calculated area; it is not suitable for precise analysis or legal coastal extent. The Who's On First publication contains retained current Quattroshapes-derived geometry that is not an independently surveyed boundary, plus a Shapely-derived geom:area_square_m field that is neither land-only nor independent corroboration. The Overture publication contains geometry that is Overture's own integration of the cited OpenStreetMap relation, not an independently surveyed boundary; its land/maritime classification was re-verified directly against the pinned release at publication time and was found to differ from this collection's original governed disposition for ten of the eleven representations. A follow-up root-cause investigation found the underlying release asset unchanged since the original capture and concluded the original capture was the error; the governed source was corrected accordingly rather than left standing.

Publication history

1. August 9, 2026 — Water-excluded borough fixture, deterministic generator and SVG published.
2. August 9, 2026 — NYC Boundaries established as the canonical knowledge resource with Linked Data metadata and multi-source comparison.
3. August 9, 2026 — Water-included geometry, retained source response and reproducible boundary overlay published.
4. August 9, 2026 — geoBoundaries and Overture Maps governed representations added with explicit Census and OpenStreetMap provenance-cluster dispositions.
5. August 9, 2026 — Five Who's On First county records added for stable identifiers, hierarchy and concordances, with default geometry retained in the Census provenance cluster.
6. August 9, 2026 — NYC Boundaries migrated to authoritative structured content blocks under fixture-page/v2; the public renderer remains backward-compatible with frozen v1 artifacts.
7. August 9, 2026 — Five 2023 Census Gazetteer county measurement records published as a public-safe JSON fixture with ALAND, AWATER, internal points, source lineage, rights, and statistical-purpose limitations; no geometry is included.
8. August 9, 2026 — Ten exact OpenStreetMap county/borough relation versions published as a public-safe metadata fixture with stable identifiers, timestamps, governed assertion links, ODbL attribution, and explicit geometry/measurement absence.
9. August 9, 2026 — Five retained geoBoundaries USA ADM2 county geometries published with CC BY 4.0 attribution, build-specific identifiers, Census provenance-cluster disposition, deterministic regeneration and explicit generalized/shoreline-clipped limitations.
10. August 9, 2026 — Five retained Who's On First county geometries published with Quattroshapes/CC0 attribution, stable WOF identifiers, Census GEOID/HASC concordances, deterministic regeneration and an explicit non-independent geom:area_square_m disclosure.
11. August 9, 2026 — Eleven Overture Maps division-area geometries published with ODbL 1.0 attribution, both Richmond County land and maritime representations, deterministic regeneration, and a disclosed land/maritime-classification re-verification finding against the collection's original governed capture.
12. August 9, 2026 — Root-caused the Overture land/maritime re-verification finding: the underlying release asset was confirmed unchanged since the original capture, and the discrepancy was traced to an error in that original capture rather than a live data change. The governed source's prose disposition was corrected accordingly.
13. August 10, 2026, 12:02 AM EDT — DCP water-excluded/water-included evidence cells now link primarily to the new /nyc-dcp-borough-boundaries/ internal source page, with the original NYC Open Data links retained alongside.
14. August 10, 2026, 6:07 AM EDT — Census Gazetteer evidence cell now links primarily to the new /nyc-census-gazetteer/ internal source page, with the original census.gov link retained alongside.
15. August 10, 2026, 6:32 AM EDT — Publication history, claim-level lifecycle/confidence, and provenance made structured (schema:Claim, prov:Activity) rather than HTML-prose-only, per docs/governance/INTERNAL_SOURCE_PAGE_PATTERN.md.
16. August 10, 2026, 7:18 AM EDT — Replaced 19 hardcoded UTC-text table cells with time/pointer nodes resolving to their governed dcterms:modified graph values, so displayed instants render in America/New_York local time like the rest of the page.
17. August 10, 2026, 7:50 AM EDT — OpenStreetMap evidence cell now links primarily to the new /nyc-openstreetmap/ internal source page, with the in-page relation-version table retained alongside.
18. August 10, 2026, 8:15 AM EDT — Publication history rebuilt to resolve every entry via time/pointer nodes instead of hardcoded prose, and DCP/Census Gazetteer dataset “Source last updated” precision corrected from date-only to the already-governed exact timestamp, per ADR-0006.
19. August 10, 2026, 8:40 AM EDT — Removed the duplicated “OpenStreetMap source versions” per-relation detail table now that /nyc-openstreetmap/ carries that content; the Compared views OpenStreetMap row links there directly instead.
20. August 10, 2026, 9:05 AM EDT — Published the Who's On First internal source page and removed the duplicated “Who's On First source records” per-record detail table now that /nyc-whos-on-first/ carries that content; the Compared views Who's On First row links there directly instead.
21. August 10, 2026, 9:35 AM EDT — Published the geoBoundaries internal source page. The Compared views geoBoundaries row now links there as its primary reference (external link retained alongside), and its build-date cell resolves via a time/pointer node instead of hardcoded prose.
22. August 10, 2026, 10:05 AM EDT — Published the Overture Maps internal source page, completing the sixth and last planned per-publisher-family internal source page. The Compared views Overture row now links there as its primary reference, with the original Overture STAC collection link retained alongside.