Report sheet LN-08 · filed 27 Sept 2026
Gleason: an 1892 flat-earth map, measured against the globe
One historic sheet, calibrated so any route can be measured twice — on the real Earth and on Gleason’s paper.
- Instrument
- labs.llc/gleason/
- Shelf on labs.llc
- Diversions · Earth
- Bench
- Local copy of the build-537 files
- Run
- 27 Sept 2026 · 20:08–20:10 UTC
- Controls
- Digital Commonwealth · David Rumsey Map Collection
- Evidence
- Source lines in the build; timed reads
Aim
Gleason is built around one document: Alexander Gleason’s 1892 ‘New Standard Map of the World’, a north-polar azimuthal layout often cited in flat-earth arguments. It shows the Boston Public Library’s scan at full resolution in a deep-zoom viewer, calibrated so modern places can be found on his layout, and measures any route twice — as a great circle on the globe and as a straight line on his paper — with the ratio. It adds his patented longitude-and-time arms, the real day and night, coastlines, a gazetteer and shareable views.
It is for map historians, teachers of projections, and anyone who wants a measured answer on the original. We tested the distance arithmetic.
Method
Apparatus: what it reads, and where the work happens
It runs in the browser on OpenSeadragon 6.1.1 for deep zoom, gleason.js for overlays and gleason-math.js for geometry, fed by seven same-origin JSON packs. The calibration is a fitted pixel model — colatitude warped by a quadratic, then an affine matrix — fitted offline (gleason-math.js 6–13). Globe distances are a haversine on R = 6,371.0088 km; paper distances use 111.195 km to the degree on Gleason’s plane (15–35).
The page states its precision: modern places land on the sheet to about ±47 km (95%), nothing finer than a scan pixel (11.1 km along a meridian), and kilometres are rounded to match (194–198). Day and night are computed per screen pixel through the calibration, with Meeus for the sun. The two arms are traced from US Patent 497,917. The provenance file records the 97 MB TIFF master down to its SHA-256; the master itself is never served.
It reads
- Boston Public Library scan (Leventhal Map & Education Center, via Digital Commonwealth; no known copyright restrictions)
- Natural Earth places, seas and coastlines
- US Census Bureau 2024 Gazetteer (counties)
- US Patent 497,917 drawings, US National Archives
- Meeus, Astronomical Algorithms (the sun)
Procedure
On 27 September 2026 (20:08–20:09 UTC) we fetched the page and its data packs from the local build-537 copy, then loaded the page’s gleason-math.js into JavaScriptCore and measured four routes with its greatCircleKm and paperDistanceKm.
Result
Fig. 11280 × 800
Fig. 2390 × 844
Table 1 · Run log, 27 September 2026
| No. | Reading | UTC | What came back |
|---|---|---|---|
| 1 | Page | HTTP 200, 91,811 bytes of HTML; engine 88,417 + 13,745 bytes; OpenSeadragon 352,735 bytes | |
| 2 | Map data packs | absent from the local tree; the server answered with the page’s HTML, so the viewer could not be exercised | |
| 3 | New York–London | 5,570 km globe · 5,944 km paper — 1.067× | |
| 4 | Oslo–Anchorage | 6,444 · 6,453 km — 1.001× | |
| 5 | Sydney–Santiago | 11,346 · 25,684 km — 2.264× | |
| 6 | Cape Town–Buenos Aires | 6,870 · 17,165 km — 2.499× |
Northern routes nearly agree with the globe; southern ones come out more than twice as long on Gleason’s paper — the map’s claim tested on its own geometry. We could not watch the viewer work: its tiles and packs ship separately from the page code and were missing locally, so its behaviour here is described from the code.
Discussion
Two controls: the same job done elsewhere on the web. Each was read on its own page on the date shown, and each is better than Gleason at something.
Digital Commonwealth — the library’s item page
Checked .
The Boston Public Library’s own record of the map: a zoomable viewer; downloads including the full-resolution uncompressed TIFF and large and medium JPEGs; a IIIF manifest; a persistent ARK identifier; the catalogue record; and the rights statement, ‘No known copyright restrictions’.
Where it is better
- The original master for download, and a IIIF manifest for other viewers.
- The authoritative record: call number, dimensions, scale.
Where Gleason goes further
- Calibrates the scan so modern coordinates land on Gleason’s layout and routes are measured twice; the item page offered no georeferencing or measuring.
- Rebuilds Gleason’s patented time arms and draws the real day and night on the sheet.
David Rumsey Map Collection
Checked .
More than 150,000 historical maps and images online, with a zoomable viewer, search of text printed on maps, MapRank geographic search, Georeferencer v4 overlays on modern maps, globes and 3D views, and high-resolution downloads.
Where it is better
- Breadth: an enormous collection against one sheet.
- General-purpose georeferencing and full-text search of map lettering.
Where Gleason goes further
- A purpose-built reading of one projection, every distance labelled twice with the ratio.
- A published error budget — ±47 km at 95%, 11.1 km a pixel — and answers rounded to it.
Sources of error: where it falls short
- It is one map.
- Place-finding is good to about ±47 km (95%) and never finer than 11.1 km a pixel — enough for the argument, not for detail work.
- No full-resolution TIFF or IIIF manifest; the library’s page has both.
- Heavy for a phone: 91,811 bytes of HTML and about 455 KB of script before any tiles.
- Our run could not load the viewer’s tiles and packs locally, so the zoom was not observed.
Conclusion
FindingNew York–London 1.067×; Sydney–Santiago 2.264× longer on the paper.
Gleason goes deep on one sheet: a fitted calibration, distances in pairs, the patent arms rebuilt, the sun computed per pixel, and every answer rounded to the error it can honestly support. Its own maths, run in our test, put the flat map’s southern distortion in plain numbers. For the master file, go to the library; for breadth, David Rumsey. For putting one famous map to the test, this.