The Charles Close Society for the study of Ordnance Survey Maps - Visit to Ordnance Survey
Note: See forthcoming events for details of another visits.
After a general introduction to the OS by Phil we were given an outline of the development, format and objectives of the new Outdoor Leisure series by Rick Morris the manager of the Outdoor Leisure, Explorer and Pathfinder Series. We then visited the section where the maps were being produced and engaged in a spirited discussion about aspects of the format and content of these maps. In particular, several members expressed doubts about the usefulness of double sided maps, especially for walkers and climbers, and questioned the technical feasibility of including an 'overlap' of 1km or so if for commercial reasons double sided maps were considered an unavoidable necessity.
The party then split into groups to observe various workstations with paired VDUs displaying raster and vector displays of identical survey areas. The staff, very patiently, explained the use of multiple files, each one containing data on specific elements of the final map, to build up layers of graphical detail and the method of updating files with information directly from the field surveyors digital notepads. Thus a map initially comprises 12 files, each holding data on individual items representing particular 'bits' of information for example; 'water detail, names and tint', 'contours, values, air heights and sand', 'boundary symbols', 'outline detail and house fills', etc. and these are further combined into 4 composite files in black, cyan yellow and magenta colour ways.
After lunch we were given a fascinating and very well illustrated talk by John Bryant about the scope and structure of the National Topographic Database, completed in 1995 and now called 'Land-line© Data' together with the commercial, social and educational uses to which it is being put and its potential, including the development of 'three dimensional virtual images' of topography which can be generated from two dimensional survey data.
We then visited the printing shop and saw the newly installed high speed press which is at present being brought into service with runs of some 8,000 sheets per hour but is apparently capable of 14,000 sheets per hour (by comparison with the existing press with a speed of some 6,000 sheets per hour). We were able to observe the whole range of processes involved in the production of 'traditional' printed maps - from the preparation of printing plates, the printing of sheets and covers, their cutting, folding and assembly into the final folded maps ready for dispatch to the retail outlets. Much interest was shown in the 'almost antique' paper assessment machine which is used to ensure the quality of each batch of paper is maintained to the OS's specification. It works simply, by cyclically folding and unfolding small sample strips of paper until they break, and recording the number of cycles achieved before failing. Apparently the paper should survive at least 600 cycles before failure to meet the required standard. Here, as elsewhere during the visit, the staff were ready and willing to enthusiastically answer all our questions, however obscure they may have thought some of them!
The Exhibition Centre was our base during the day and venue for the introductory talks. At intervals during the day and at the end of our visit we were able to browse through the singular collection of historical exhibits illustrating the origins and development of the OS. This archive material is well worth a visit in its own right and includes all manner of artefacts related to the development of survey methods and the processes for transcribing the information onto paper, from the origins of the service to the present day. Included are some of the 'legendary' surveying instruments with personal items and records of the far sighted individuals without whom the accuracy, reliability and comprehensiveness of OS maps could not have evolved. Apart from the usual shortage of time to ask more questions and browse for longer over the exhibits on display, our only regret was that the 'part-time' visitor shop could not be staffed during our visit. I suspect the OS's financial IOSs on this occasion was considerable. Given the exceptional enthusiasm of CCS members as potential purchasers for all things OS, and despite our small numbers, we would probably have cleared most of their stock.
Gerry and the staff of the OS are to be congratulated on a
well organised and very informative day, especially for those
members, such as myself, who were previously unfamiliar with all
the 'mechanics' of map production and the scope and scale of national
and international work now being undertaken by the Survey, particularly
in the development of GIS, GPS and other uses for digital map
data.