The Gazette 1979

JANUARY/FEBRUARY 1979

GAZETTE

MAPPING AND THE ROLE OF THE ORDNANCE SURVEY This article has been prepared through the kind co-operation of the Assistant Director, Ordnance Survey Office, Phoenix Park, Dublin.

While the Ordnance Survey is recognised as the official central survey and mapping organisation for the country, the full scope of its operations are not widely appreciated. It is responsible for geodetic surveys, topographical surveys and the production of maps at various scales from these surveys. The historical roots of the organisation go back some hundreds of years, but its activities today evolved from decisions taken by a Committee set up by the then Minister for Finance in 1964 to advise on the mapping requirements of the State. At present the main task is to bring the 19th and early 20th century 1:2500 maps up to date and to produce and maintain up to date surveys at 1:1000 scale for urban areas. The older maps were surveyed and published on a county basis showing no detail beyond the county boundary. New mapping is surveyed and published on a National basis and is drawn on a Transverse Mercator projection. The Mapping Plan The main recommendations of the 1964 Committee were: Ireland should be surveyed and mapped on a National basis (Transverse Mercator, National Grid). The standard Ordnance Survey (O.S.) scales would be: Large scale: I 1:1000, for urban areas, towns and

1:2500 (25 ins), 1:5000, and 1:10560 (6 ins) maps are considered to be large scale. It is always difficult to define the status of a product or an organisation at a time of great change and this is the position in which the Ordnance Survey and its mapping finds itself at this time. The old is still with us and new has not arrived (except for some of the 1:1000 urban mapping). Since the last large scale survey (1:2500 or 25 ins) at the end of the 19th and the beginning of the 20th century only five counties have been completely revised. Other counties have had partial revision carried out. The 1:2,500 mapping was surveyed and published on a county basis and covered the country with the exception of some mountainous areas, some areas of bogland and islands. These areas were surveyed and published at 1:10,5000 scale. (1:1250 or 50 inch maps were photographic enlargements). This was still the position for rural mapping up to 1978 when the first new 1:2500 maps surveyed on a National basis were published for Limerick. The first 1:5000 derived maps with five metre contours were also published. These are the first steps in a 25 year remapping programme for the State. Urban mapping has, since 1968, been surveyed on a National basis and this programme is now nearly half-completed in terms of map sheets to be surveyed and published. The Ordnance Survey now has two large scale mapping programmes running in parallel: It is planned that the urban mapping programme will be completed within the next eight years, (an urban area is defined as one with a population of a 1,000 or more according to the census records) and this mapping will be maintained on a continuous basis as well as cyclic basis. Derived maps are now becoming available at 1:2500 scale for some urban areas. Urban mapping will not in the future be restricted to locations where rural mapping is also taking place; urban surveys will proceed independently. Rural mapping at 1:2500 scale will be the main task of the Ordnance Survey over the next 25 years. Maps at 1:5000 scale will be derived from these and in addition will have contours at five metre intervals. It is not proposed at this time to replace the 6 ins map. Using present compilation methods the publication of a 1:5000 series and 1:10,000 series would be prohibitively costly. Developments in compilation methods, however, indicate that 1:10,000 mapping could be provided in the near future should there be a demand for it. Main mapping efforts are now centred in the Limerick, Waterford and Galway areas. The names of counties only indicate general locations and, in fact, the Limerick centre includes parts of Clare and will soon include Tipperary. It is hoped to open other centres within the next few years 13 (1) Urban Mapping. (2) Rural Mapping.

villages with a population of 1000 or more. Number of plans 5000 in State. Plan size — 600 x 800mm. II 1:2500. Base scale for all Ireland. Number of plans 30,000. Plansize 600 x 800mm. Ill 1:5000. Derived Mapping for all Ireland. Number of Plans 7500. Plan size 600 x 800mm.

Small scale: IV 1:25,000 for all Ireland. V 1:50,000 for all Ireland. VI 1:100,000 for all Ireland. VII 1:250,000 for aU Ireland. VIII 1:500,000 for all Ireland. Mean sea level would be adopted as datum for height information. Contours at five metre intervals would be shown on the 1:5000 sclae map. The large scale mapping programme was first priority. How the policy was to be implemented was left to the Ordnance Survey. Large Scale Maps In the Ordnance Survey the 1:1000, 1:1250 (50 ins.)