Marker corpus

markers.json.gz — the complete corpus, gzipped JSON, one record per marker. 682,560 records, 13.7 MB compressed, 121.7 MB expanded.

It is gzipped because it outgrew what the host will serve as a single file, not to make it awkward. gunzip markers.json.gz, or read it in place — Python's gzip.open, zcat and curl --compressed all handle it without unpacking to disk first.

Each record carries:

• id — stable identifier, prefixed by source
• name — the marker's name, used for triage rather than shown in the game
• latitude / longitude
• source — where the coordinate came from (see below). ngs (613,497), nrhp (67,141), osm (1,922).
• kind — what sort of thing it is. Ten values, and here is the whole list with its counts in this file, because a partial vocabulary is how a consumer writes a parser that silently drops a fifth of the data: survey (576,576), place (58,088), infrastructure (19,667), structure (17,766), monument (7,109), district (2,701), art (418), view (126), water (72), nature (37).
• access — how reachable it looks, where it is known at all. It is known for 125,849 of the 682,560 records — 18.44%. On the other 81.56% the key is not merely empty, it is absent, and absence means nobody has classified it, never that it is safe. Where present the values are roadside (42,715), parking (37,349), nostop (24,705), remote (12,572) and private (8,508) — computed from OpenStreetMap road, parking and landuse context, except nostop, which is taken from the NGS setting code and means the object is set in a bridge abutment or pier, or in a street pavement or curb.
• marker_code — the source's own object code, carried through unchanged rather than reinterpreted. For ngs records this is the NGS monument/structure code (DB disk in bedrock, DD disk in a structure, I metal rod, and so on); 106 distinct values appear.
• last_cond — the NGS condition from the most recent recovery report: GOOD (398,493), MONUMENTED (180,138), FIRST OBSERVED (16,709), POOR (11,279), SEE DESCRIPTION (6,878), and absent on the 69,063 non-NGS records. It is a report of what somebody found on the day they looked, sometimes decades ago, not a promise about today.
• verified — whether a human has actually laid eyes on it

The corpus is published under the Open Database License (ODbL) v1.0.

Part of it is extracted from OpenStreetMap, which is ODbL and share-alike on derived databases. This file is a database of records extracted from OSM rather than a rendered map, so under any honest reading it is a derivative database and share-alike attaches. We did not go looking for a reading that avoided it.

The corpus was never the point. The game is an instrument — a bearing, a range, a sound, and a deliberate refusal to route you. Publishing the pointer costs nothing that matters and settles the question permanently.

The application source is not covered by this license. ODbL governs the database; the app is a separate work.

• OpenStreetMap (osm) — map data © OpenStreetMap contributors, ODbL. The access classification is computed against OSM geometry and is OSM-derived for that reason.
• National Register of Historic Places (nrhp), National Park Service — US public domain
• NOAA National Geodetic Survey (ngs) survey marks — US public domain
• USGS Geographic Names Information System (gnis) — US public domain
• HABS/HAER (habs), Library of Congress — US public domain
• Wikidata (wikidata) — CC0

HMdb.org is deliberately not in this pipeline. It has the best roadside-marker corpus in existence and restricts commercial use without written permission, so none of its content has been used. The ref:hmdb tag appears on some OpenStreetMap records; that tag is OSM's, not HMdb's content.

No marker text. Not an omission — the whole design. Supply the inscription and the destination becomes redundant: why drive there if the phone already told you? The words are already deployed in the world, bolted to a post, in fifty states, at public expense. The game is a pointer at them.

No observed data. Which markers turned out to be gone, fenced off, or impossible to stop for — plus verifications, photographs and per-marker difficulty — is collected by actually driving to them, and it lives in a separate database that is not published here. This file is the input; that one is the work.

No warranty of any kind. These are coordinates, not directions. Some point at private land, some at things that no longer exist, and some at places with nowhere safe to stop. Use your judgement, and do not trespass.

Nothing is filtered out for safety. The game refuses to send anyone to a marker flagged private or nostop, and those records are still here — a general-purpose corpus that silently dropped records to suit one game's safety rule would be lying by omission to everyone else, and a surveyor is exactly the person who wants the bridge marks.

But do not read that as a safety classification you can rely on. In this file the game's refusal has 33,213 records to act on out of 682,560 — 8,508 private and 24,705 nostop — plus 3,360 aids to navigation refused separately, on their object code, because a daybeacon on a piling stands in open water and no road reaches it. The classification is in the data for 18.44% of it. For the other 81.56% there is no judgment recorded either way, and treating a missing access key as a clean bill of health gets it exactly backwards. The decision is yours, and on four records in five it is yours without help.

The one thing that is excluded at ingest: NGS marks whose last recovery report says MARK NOT FOUND. Somebody went and looked and it was gone. That is roughly 22% of the marks in a given state.

The survey marks are now here. 576,576 NGS marks — brass disks, rivets and chiselled squares set flush in the ground — were withheld from the first release for bundle size, and that reason is gone: the app now reads a packed binary corpus and carries all 682,560 records in 34 MB. The previous version of this page said they would return in a later release. This is that release.

They arrive with their safety classification already attached, which is why the nostop count above went from zero to 24,705 — survey marks concentrate on bridge abutments and pavements far more than any other source, and that was always the field's real subject.

Nothing is withheld at all. This file is the database the app ships, exported from the bundle itself rather than assembled alongside it, so there is no version of the corpus that the app has and you do not. All 1,922 OSM-derived records are here, and so is everything else.

And if survey marks are what you came for, the source still beats us: NOAA publishes the complete dataset as monthly per-state shapefiles at geodesy.noaa.gov/pub/DS_ARCHIVE/ShapeFiles/<ST>.zip, carrying the recovery history and datasheet text this project deliberately discards.

Found a marker that is wrong, gone, or somewhere dangerous? Email [email protected]. Corrections to the underlying map data are better made upstream at OpenStreetMap, where everyone gets them.