Ordnance Survey Maps - 25 inch 1st edition, Scotland, 1855-1882

Introduction

The Ordnance Survey 25 inch to the mile series (1855-1882) is immensely valuable for local history.

This series (1855-1882), is the earliest detailed mapping for all the inhabited regions of Scotland. All towns, villages and cultivated rural areas were mapped, comprising over a third of the total land area of Scotland.

The maps are immensely valuable for local history, allowing practically every feature in the landscape to be shown. They provide good detail of all buildings, streets, railways, industrial premises, parkland, farms, woodland, and rivers. Their bold style and attractive, informative, hand-colouring allow easy interpretation for a wide range of uses.

In this section

Background

Initial surveying of Scotland by Ordnance Survey was carried out at the less detailed scale of six inch to the mile mapping. This had been the scale used in Ireland from the 1820s, and continued in northern England and Scotland in the 1840s. However, there were protracted debates as to whether this was the correct basic scale (i.e. the largest practical scale for surveying). The six inch scale allowed more rapid progress to be made, and was often satisfactory for moorland and uncultivated areas, but the 25 inch scale had a number of advantages in more populated regions.

The 25 inch maps were more useful for:

The Battle of the Scales, as it became known, was a protracted debate during the 1850s, over whether the six inch or 25 inch should be the basic scale. In 1855, the 25 inch was officially authorised as the basic scale for all cultivated rural areas. In 1857, the 25 inch series was temporarily discontinued, but it was re-authorised again in 1858.

The 25 inch series has continued through to the present day, with the six inch and one inch maps derived or reduced from the larger scale. The 25 inch or 1:2,500 still forms the most detailed mapping of rural areas in modern Ordnance Survey digital data.

Geographical coverage of Scotland

Geographical coverage of the 25 inch maps across Scotland
Geographic coverage of the
25 inch maps.

Six Scottish counties have no 25 inch mapping before the 1890s:

These counties and the Island of Lewis had been surveyed at the six inch scale, before the decision to survey at 25 inch in 1855.

The other principal areas without 25 inch mapping are the uncultivated, mountainous and moorland regions, particularly in the Highlands.

Surveying proceeded generally from south to north. Most of the Lowlands were surveyed by 1859, and most areas south of the Highland Line were surveyed before 1869. Orkney and Shetland were the final counties to be surveyed in 1877-1878.

Surveying and levelling

Survey work was based on triangulation by teams of eight to 12 men on the ground, using standard chains and theodolites. Levelling work created a set of accurate heights, either on permanent features (benchmarks) or as spot heights (e.g. road centres). The 25 inch maps show benchmarks and spot heights, but not contour lines, which appear on six inch maps and smaller scale maps.

Sheets, numbering and parishes

Before the Second World War, all detailed Ordnance Survey maps were based on local county projections and meridians, and all sheets carried the relevant county name. (Read more about OS county projections). The 25 inch sheets were laid down as a set of 16 sub-sheets within each parent six inch sheet. Their two sheet numbers therefore reflect, first, the relevant six inch sheet (usually a Roman numeral), and second, the relevant sub-sheet, 1-16. Typical 25 inch sheet references take the form:

Sheet numbering of the six inch and 25 inch maps
Sheet layout of the 25 inch maps.

Each 25 inch sheet covers a distance on the ground of 1.5 miles (west-east) by 1 mile (north-south). Each sheet measures 96.6 cm (38.016 inches) by 64.4 cm (25.344 inches) within the map neat line. The true scale is 25.344 inches to the mile, so being a metric 1:2,500 scale map.

Parish editions

Before the 1870s, sheets were published as separate parish sets, so that for sheets containing two or three parishes, there were two or three separate parish sheets published for that map sheet area. Anywhere beyond the specific parish appears blank, and it is necessary to consult the adjacent parishes to see the mapping for these blank areas.

For this reason, when users select 25 inch maps on this website for any particular location, they may get more than one map sheet.

During the 1870s, these separate parish sheets were replaced by combined parish sheets, completely filling the map sheet area in one published sheet.

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