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GAZETTE
JANUARY/FEBRUARY 1979
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
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.)
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:
(1) Urban Mapping.
(2) Rural Mapping.
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
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