There are several questions that are helpful to consider when looking at either a single map, or comparing a number of different maps and plans.

What is the scale and orientation of the map?

Is the map large-scale or small-scale? Maps at a larger scale show a smaller area in a greater amount of detail than those at a smaller scale. For example, compare the depiction of buildings between a 6-inch to a mile (less detailed) and 25-inch to a mile (more detailed) Ordnance Survey map. On a 6-inch map, the buildings shown are more stylised. Similarly, a map of the county is less likely to depict individual buildings than a map of a village or town, e.g. Jeffreys’ map of Yorkshire of 1771 (see our introduction to historic maps and guide to historic map regression webpages)

Sometimes, particularly on earlier maps and plans, buildings are shown in profile. Where such houses are depicted on maps, they may be illustrative only and indicative of the nature of a building, rather than accurate depictions of the actual structure.

Older maps may use historic units of measurement, such as chains, feet and yards. Similarly, areas were often measured in acres, roods and perches.

Think about the orientation of the map. Ordnance Survey maps are drawn according to the National Grid, with north facing to the top. Older maps may, however, be oriented differently. Ensure maps are aligned the same way up when making comparisons between them.

Handy guides to the abbreviations and map symbols on the various scales and editions of Ordnance Survey maps are available via the National Library of Scotland website.

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What is the date of the map?

An Ordnance Survey map sheet will record the  date(s) it was surveyed and/or revised, which may be a few years prior to its publication date. These dates are important to note because any changes to property between the survey/revision and publication dates are unlikely to be mapped.

Sometimes, estate maps and plans are undated. It may be possible to estimate an approximate date based upon a watermark in the paper the map is drawn or printed on, or based on the style of the handwriting. In some cases, a terminus post quem can be assigned, that is a date after which a map must have been drawn, because it shows a particular building or man-made feature of a known date, such as a railway line (although be sure that this feature has been built and it is not a proposed plan!).

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TIP: Always question what you see! Where possible, verify your findings with more than one type of evidence.

Just because something is drawn on a map or plan, does not always mean that it was built; some plans might be showing proposals that were never, or only partially, implemented. Think about why the map was drawn up (see below).

Similarly, a building shown on an old map may not be the same building that stands on the site today. It may, for example, have been demolished and rebuilt in the same place.

If a building or feature is not shown on a particular map, this does not necessarily mean that it was not there. Absence of evidence is not always evidence of absence!

Be aware that spellings of house and place-names may change over time.

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Why was the map produced, and for whom?

Estate maps and plans were generally produced to record the land and buildings belonging to a particular estate or landowner. Therefore, they may not show all of the land in a particular parish or township, although they may note the names of the landowners of adjoining areas.

Similarly, tithe maps may not record an entire parish as not all areas may have been liable for tithes. As they were primarily concerned with surveying land to assess its titheable value and record ownership, buildings and settlements may have been mapped in lesser detail, or omitted altogether.

Likewise, enclosure maps may leave areas of villages blank as their main purpose was to show the subdivision of land, mapping field boundaries and roads but not necessarily settlements.

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