Ordinance Survey Maps

How OSi Maps are made
Aerial photogrammetry is the method of surveying undertaken by the OSi to compile Ordinance Survey maps at 1:5000, 1:2500 and 1:1000 scale maps.
An aircraft, with a camera mounted on the underside of the fuselage, is flown in a grid pattern at 40,000 feet to produce a series of overlapping photographs of the land below.
These photos are orthographically corrected to compile a survey drawing from them. This is a very cost effective method of producing maps, but it does have certain limitations, eg detail under tree cover may be less accurate. A ground survey is a far more accurate method of surveying land.

OSi Map Reference Systems.

The above mentioned aircraft has two high end GPS receivers mounted on its wings, these provide the essential positional data for the mapping process. The OSi use GPS reference to establish the position of their mapping detail.

Professional Land Surveyors also use GPS grid reference too, which means that Professional Surveyors are singing from the same hymn sheet as the Ordinance Survey digital mapping system. As land Surveying is a more accurate method of surveying, professional surveyors are in a position to check and verify the accuracy of Ordinance Survey maps.

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Phone: 086 2535285
Email: paudie@baselinesurveys.ie
Baseline Surveys Ltd, Mount Desert Lodge, Lee Road, Cork