Cahill-Keyes bibliography and source provenance

Documentation index · Geometric context · Implementation notes

This bibliography separates the implementation’s direct source from design specifications, historical Cahill material, related software, and rendering assets. Web resources were last checked on 2026-08-01.

Direct implementation source

1. Graça, Mary Jo, and Gene Keyes. “MegamapMaker-prep9.” Perl source, 2012-03-15, with additional notes dated 2013-11-28. Repository copy.

   This is the authoritative source for the C++ port. In particular, its Preliminary, LLtoMP, MPtoXY, and MJtoMM subroutines supply the scaffold, geographic normalization, A–L zones, supple-zone construction, and standard eight-octant M-layout. The header credits Keyes with the design and calculations and Graça with the program. It also contains the applicable non-commercial-use, attribution, modification, redistribution, and commercial-contact language.

2. Graça, Mary Jo, and Gene Keyes. “MegamapMaker-prep9.pl.” Enrico Spinielli’s public source mirror, created 2012-12-12. GitHub Gist.

   The repository copy, rather than the mirror, is used for reference outputs and line-by-line translation. The mirror is useful as an independently hosted copy and for source history.

Gene Keyes specifications and development record

1. Keyes, Gene. “Cahill-Keyes Megamap Principles & Specifications.” CKOG in Apache OpenOffice, part 1.

   This is the primary geometric specification used to understand the numeric construction. It describes the 10,000-unit octant scaffold, 40,000-unit M-layout span, use of a single mirrored half-octant, three meridian-angle regimes (m, 2m/3, and m/3), polar spacing, equisection, and supple transition zones.

2. Keyes, Gene. “Cahill-Keyes Octant Graticule and Grid.” 2011-01-12. CKOG construction illustrations, part 7.

   The construction sequence illustrates longitude/latitude input, normalization to one half-octant, conversion to Cartesian template coordinates, and assembly of the eight-octant map. It is the best visual companion to the C++ numeric pipeline.

3. Keyes, Gene. “Ongoing Development of the Cahill-Keyes Multi-Scale Megamap: Papers and Prototypes, 1973–2014.” Updated 2014-09-21. Development index.

   This curated chronology links the evolving principles, prototypes, Graça’s programs, comparison maps, and third-party implementations. It also records Keyes’s development work from 1975 onward and Graça’s programming work beginning in 2010.

4. Keyes, Gene. “Zooming to Crimea in the Cahill-Keyes Multi-Scale Megamap, Beta-2.” 2014-03-11. Beta-2 Foxit demonstration.

   This demonstrates the projection as a large vector “megamap” that remains usable across scales, and provides context for the source program’s Beta-2 construction.

5. Keyes, Gene, compiler. “B.J.S. Cahill Online Resource: Octahedral Map of the World.” 22nd edition, 2016-09-14. Cahill resource and bibliography.

   This is the principal index to Cahill’s original publications, patents, diagrams, later commentary, and Keyes’s development. Bibliographic details for the historical entries below follow this resource.

B.J.S. Cahill historical sources

1. Cahill, Bernard J.S. “An Account of a New Land Map of the World.” Scottish Geographical Magazine, September 1909, pp. 449–469.

   The first publication of Cahill’s Butterfly world map and octahedral approach, as catalogued in Keyes’s B.J.S. Cahill Online Resource.

2. Cahill, Bernard J.S. “Map of the World.” U.S. Patent 1,054,276. Filed 1912-03-05; issued 1913-02-25. Patent text and drawings.

3. Cahill, Bernard J.S. “A Land Map of the World on a New Projection.” Journal of the Association of Engineering Societies, October 1913, pp. 153–207.

4. Cahill, Bernard J.S. “A World Map to End World Maps.” Geografiska Annaler, 1934, pp. 97–108.

These works establish the octahedral and Butterfly context from which Keyes’s redesign developed. The C++ code implements the later Cahill-Keyes graticule specified by Keyes and programmed by Graça; it is not a direct transcription of Cahill’s 1909 projection.

Related implementations

1. Fil. “Cahill-Keyes projection.” Observable notebook. Interactive implementation.

   This provides an interactive JavaScript implementation useful for visual comparison. It is not executed by the native C++ projection.

2. Spinielli, Enrico. Public mirrors and D3 experiments linked from Keyes’s development index, including the Graça/Keyes Perl source mirror cited above.

Related implementations are comparison material only. Reference coordinates for the tests were generated from the checked-in Perl source.

Repository map and test artifacts

1. Visionscarto. “Cahill-Keyes 44 × 22.” SVG map asset, 2018. 44-by-22-inch SVG.

2. Visionscarto. “Cahill-Keyes 44 × 22, inverse.” 300-DPI PNG map asset, 13200 × 6600 pixels. Inverse raster.

3. Visionscarto. Compact Cahill-Keyes SVG map asset. Compact SVG.

The large SVG establishes a 4224 × 2112 logical coordinate example, while the PNG establishes the 13200 × 6600 raster example. Both are exact 2:1 frames and motivated the variable-size frame.frame_area interface. The public projection’s one-degree longitude adjustment preserves registration with this asset family.

1. cartofreako contributors. Native mathematical verification. test-cahill-keyes-projection.cc.

2. cartofreako contributors. Public API and variable-frame verification. test-cahill-keyes-projection-api.cc.

3. alpha60 contributors. Geographic integration anchors. augment_carto_geo_specific.

Source-to-implementation map

Documentation index · Geometric context · Implementation notes