Sources
The master list of authorities Coordinately cites — primary first, then secondary.
By Steve K.. Published . Last updated .
This is the master list of authorities Coordinately cites across the site. Tier 1 entries are primary sources — government bodies, standards organisations, the original publishers of the data. Tier 2 entries are authoritative secondary sources, used for historical and narrative context but never for foundational numerical claims.
The rules that determine when each tier is appropriate live at /editorial-policy. The procedural record of how this list is maintained lives at /methodology.
Tier 1 — primary sources
Used for foundational facts and all numerical claims. Where two primary sources document the same fact, we cite the one whose publication is closest to the original measurement or standard.
| Code | Source | Best for |
|---|---|---|
| BIPM | Bureau International des Poids et Mesures bipm.org | UTC definition, time standards, the SI base unit of time |
| EPSG | EPSG Geodetic Parameter Dataset epsg.org | Coordinate system registry, projection identifiers |
| ESA | European Space Agency esa.int | Galileo satellite system, European satellite navigation |
| FAA | Federal Aviation Administration faa.gov | GPS in aviation, WAAS, flight-navigation standards |
| GPS.gov | National Coordination Office for PNT gps.gov | Civilian GPS performance, accuracy figures, programme operations |
| IAG | International Association of Geodesy iag-aig.org | Global geodesy standards, ITRF and IGS coordination |
| IANA | Internet Assigned Numbers Authority iana.org | Time zone database (the tz / Olson database) |
| ICAO | International Civil Aviation Organization icao.int | International aviation coordinate standards |
| IERS | International Earth Rotation and Reference Systems Service iers.org | Earth orientation parameters, ITRF, leap seconds, UT1−UTC |
| IGN | Institut Géographique National (France) ign.fr | French coordinate systems, RGF93, Lambert projections |
| IHO | International Hydrographic Organization iho.int | Nautical charts, hydrographic standards, marine geodesy |
| ION | Institute of Navigation ion.org | Peer-reviewed navigation papers and conference proceedings |
| ISO | International Organization for Standardization iso.org | ISO 6709 (geographic point format), ISO 8601 (dates) |
| LoC | Library of Congress loc.gov | Historical primary sources — the 1884 IMC, cartographic history |
| NASA | National Aeronautics and Space Administration nasa.gov | Earth observation, satellite missions, Earth science |
| NGA | National Geospatial-Intelligence Agency nga.mil | WGS84 ellipsoid, MGRS, Bowditch (Pub. 9 navigation handbook) |
| NGS | NOAA National Geodetic Survey geodesy.noaa.gov | US datums, reference frames, geoid models, NSRS modernization |
| NIST | National Institute of Standards and Technology nist.gov | Time, frequency, units, measurement uncertainty |
| NMM | National Maritime Museum, UK (Royal Museums Greenwich) rmg.co.uk | Longitude history, John Harrison, the Royal Observatory |
| NOAA-NCEI | NOAA National Centers for Environmental Information ncei.noaa.gov | World Magnetic Model, magnetic declination, geophysical data |
| NRCan | Natural Resources Canada nrcan-rncan.gc.ca | Canadian Spatial Reference System, NAD83(CSRS) |
| OGC | Open Geospatial Consortium ogc.org | Open geospatial standards — WMS, WFS, GeoJSON |
| OS | Ordnance Survey (UK) ordnancesurvey.co.uk | British National Grid, OSGB36 datum, UK topographic mapping |
| USGS | US Geological Survey usgs.gov | Topographic mapping, projection mathematics (Snyder), 3DEP elevation data |
Tier 2 — authoritative secondary
Used for historical, biographical, and narrative context. Tier 2 citations never stand in for a Tier 1 citation when one is available for the same claim.
| Code | Source | Best for |
|---|---|---|
| Britannica | Encyclopaedia Britannica britannica.com | Historical and biographical context — never numerical claims |
| NatGeo | National Geographic nationalgeographic.com | Cartographic history, projection adoption, popular geography |
What this list is not
It is not exhaustive. Individual articles cite additional papers, books, and government publications that are topic-specific — for example, T. Vincenty's 1975 paper on ellipsoidal geodesics, or the Bowditch handbook of navigation (NGA Publication 9), or USGS Professional Paper 1395 (Snyder's “Map Projections — A Working Manual”). Those sources are cited inline where they are used.
It is also not stable forever. Bodies merge, URLs change, and the primary authority for a topic occasionally shifts. The list is reviewed quarterly; the review date appears in the byline at the top of this page.
How to add a source
If you know of a primary authority Coordinately should cite that is not on this list, send the URL and a one-sentence description of what it is the primary source for to info@coordinately.org.
We add sources that meet three criteria: the source is a primary authority for a topic Coordinately covers; the source is actively maintained or remains the canonical reference; and the source is not redundant with one already on this list. If a suggested source does not fit, we explain why.
Related
- Methodology— How content is sourced and verified
- Editorial policy— The full source-tier rules
- Accuracy— Per-tool and per-article accuracy disclosure
- About— About Coordinately
Frequently asked questions
How do you decide which sources to include?
A source qualifies for this list when it is a primary authority for a topic Coordinately covers, is actively maintained or remains the canonical reference, and is not redundant with a source already listed. Sources we cite only occasionally for context — peer-reviewed papers, government statistical agencies for population data — may not appear here even when individual articles cite them.
Is this list complete?
No. It is the master list of recurring authorities. Individual articles cite additional papers, books, and government publications that are topic-specific (for example, a /learn/datum-transformations article will cite NGS NADCON documentation in addition to NGS itself). The master list captures the broad authorities that show up across many articles.
How often is this list reviewed?
Quarterly. We check that the URLs still resolve to authoritative content, that no listed source has been deprecated or merged into another body, and that any new authority worth adding is added. The review date appears at the top of this page.
How do I suggest a source?
Write to info@coordinately.org with the URL and a brief note about which topic it is the primary authority for. We add sources that meet the criteria above; we explain when we do not.
What about sources for historical content?
For history (the 1884 International Meridian Conference, John Harrison and the longitude problem, the development of the metric system), we cite the Library of Congress, the National Maritime Museum, and the original conference proceedings where they are available online. Tier 2 secondary sources (Britannica, National Geographic) are used for narrative context.
Cite this article
APA format:
Steve K. (2026). Sources. Coordinately. https://coordinately.org/sources
BibTeX:
@misc{coordinately_sources_2026,
author = {K., Steve},
title = {Sources},
year = {2026},
publisher = {Coordinately},
url = {https://coordinately.org/sources},
note = {Accessed: 2026-06-05}
}