Handwritten note (1957): project for a "luminous map" for car navigation

In this document

The principle of the "luminous map"

The note, dated 15 September 1957, sets out the idea of a road map photographed on 8 mm film, divided into three scale levels: "1° Ensemble" (Overall), "2° par éléments d'une certaine échelle" (by elements of a certain scale), "3° les points particuliers (ville) de chaque élément, à grande échelle" (specific points (towns) of each element, at large scale) p. 1. The film would be projected inside the vehicle onto a "luminous screen with variable intensity", with "location tracking" and "automatic search" p. 1.

Feasibility calculations

The author details a metric calculation: an 8 mm film has "262 images per metre", i.e., 3930 images for 15 metres of film p. 1. He compares this to the surface area of a Michelin map ("1100 m x 480") and estimates that about 24 images per map would be needed, i.e., "less than 1000 images" to cover the whole of France (40 maps x 24 = 960) p. 1.

The advantages listed include "variable magnification", "variable illumination", "faster search" and the possibility of presenting "details", "warnings" or "views", as well as "magnification of tricky spots" p. 1. A disadvantage is also noted: "less luminous", "not practical" p. 1.

Cost estimation and extensions (p. 2)

The second page compares a cost of "4000 x" for 40 maps (at 100 x per unit) to the price of "a colour film" of "1700 x", the latter allowing 3900 images against the 960 required p. 2.

The author then considers "possible films for specific itineraries", usable "in one direction" and "in the other", with "photo views of intersections or town crossings" and a "mileage indicated on each view", to be compared with the actual mileage of the car p. 2. A grid of numbers and a list of codes ("Ao A1 A2", "Bo B1 B2") accompany these notes, without their exact function being explained in the text p. 2.

Context

This reflection is situated in the years following the release of the DS (1955), a period when Paul Magès, a Citroën engineer best known for the hydropneumatic suspension, explored various avenues of on-board innovation. As GPS did not yet exist, the idea of an on-board visual guidance system was a notable anticipation for the time — paper Michelin maps being the only reference for car navigation then.

Archivist's perspective

This document bears witness, it seems, to a lesser-known facet of Magès' work: beyond suspension mechanics, an interest in driving assistance and the ergonomics of the cockpit. The numerical reasoning — cost of maps, film capacity, number of images — shows an engineer's approach seeking to validate the economic viability of an idea before any technical development.

It is likely that this note remained at the personal sketch stage, with no industrial follow-up attested in this document. It nevertheless deserves to be compared with other secondary projects of Magès concerning instrumentation or driver assistance, if such archives exist in the collection.