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Virtual Museum

The Charles Close Society Virtual Museum

These pages are intended as a repository for technical details of how maps were produced in the pre-digital era. They form part of a Europe-wide initiative coordinated by the EuroSDR's Working Group on the Preservation of the Geographical Production Process (ESDRPGPP). EuroSDR - the European Spatial Data Research Network - is an organisation linking National Mapping Agencies with research institutes and universities - see .

They are a mixture of electronic documents and images which can be viewed by visitors to the site with selected references to archived material. Much of this material - references of the form univmaps/CCSA/... - is in the Society's archives held at Cambridge University Library. The catalogue for this archive is held on the university's JANUS catalogue; for access to the material see References of the form PC9001/... are to material in private collections; for access contact the administrators of this virtual museum.

Copyright of the electronic documents remains the property of their originators.

Additions to the museum and comments and suggestions are welcomed: please contact the Chairman of the sub-committee Rob Wheeler

These pages represent a work in progress. It is our intention to provide properly-curated 'virtual exhibitions' in due course, but for the present all our energies are focussed on building the collection.

The site is not intended for the display of maps themselves. For those wishing to see the products of the Ordnance Survey, a good starting point is our Sheetfinder page at A selection of notable or unusual maps is at and in the digital archive at



Plan examiner's board and carrying-case. c1980. Metal & perspex with waterproof covers. 54x54cm; internally 48x48.5cm. (NB: Standard large-scale plan was 40x40cm between neatlines.) ACC1301

Pocket Sextant, used to survey minor detail at 1:2500 and 6 inch to the mile / 1:10,000 (paths through woods etc). ACC1302

Microptic Alidade, used on Plane Table work, mainly for 6 inch to the mile / 1:10,000. ACC1303

Prismatic Compass, used for minor detail on 1:2500 and 6 inch to the mile / 1:10,000. ACC1304

Abney Level, used for correcting slope distances to horizontal on Chain Survey. ACC1305

Wild T2 theodolite - the main workhorse for the supply of control (PTSs and RPs etc). ACC1306

Wild T16 theodolite - used for survey traverses before the introduction of the Kern DK-RT Self Reducing Tacheometer Theodolite. ACC1307

Kern DK-RT Self-reducing Tacheometer Theodolite photographs and OS Instruction manual ACC1310

Double Prism Optical Square (used during detail survey to place the surveyor on line between two points and to raise an offset at 90 degrees from that line). ACC1315

Double Prism Optical Square Instruction leaflet from York Survey Supply, a cosmetically different instrument from ACC1315 above but used in exactly the same way). ACC1312

Metric levelling staff with transit box. ACC1314

5 inch Tavistock theodolite, used for high order control. (A smaller 3.5 inch Tavistock was used for lower order control, and latterly on the 1:2500 Overhaul of the County Series mapping.) can be seen on University of York Digital Library pages at

Artillery Director, used on Chain Survey traverses and also for minor detail traverses on the Overhaul can be seen on British Ordnance Collectors Network at


OS Triangulation Pillar ACC1308

OS Beacons ACC1309

Control Point for Air Survey. Enugu, Nigeria, 1976 ACC1501



CTS500 Geodetic level manufacturer's manual. used pre-1939. See also ACC1313 below. ACC1311

Photographs of S500 Geodetic Level (as ACC1311 above). ACC1313



Stereoscope Universal Type SV.3, C.F.C.This is a later version of the “Casella SV2 Mirror Stereoscope”, employed extensively by OS surveyors engaged on 1:2500 “Overhaul” in the period 1965 – 1980 to observe stereoscopic virtual terrain models using overlapping aerial photographs. ACC1315