HOW  GOOD  IS   THE  MAP ?

blue arrow Most Land Registry filed plans are produced at 1:1250 scale. The thickness of the line on the map actually represents 10 inches (25 cm) on the ground.

blue arrow Other filed plans are either produced at 1:2500 scale (rural areas) or are enlarged to 1:1250 from 1:2500 scale. On both of these the thickness of the line on the map actually represents 20 inches (50 cm) on the ground.

Compare those line thicknesses with the average larch-lap panel fence, supported on fence posts only 7.5 cms (3 inches) thick!

Line thickness is not the only consideration when trying to interpret the map onto the ground. Map accuracy is a major factor. Ordnance Survey have over many years tested the accuracy of a large sample of their published maps. As a result they have published an accuracy statement for their large scale maps. You can find it at http://www.ordnancesurvey.co.uk/productpages/landline/positional-background.htm

Because the accuracy depends on scale and method of survey, you will need to find out these details for the Ordnance Survey map of the area covering your property. Go to the Ordnance Survey web site and click on "Tile selector" and use one of the methods offered in order to find the "thumbnail" map of your area. The page presented will give the details you need in order to interpret the accuracy statement.

The accuracy statement will tell you that even in the best of circumstances (a 1:1250 scale map), whilst some of the lines will be spot on, you can expect the position of any line on the map to be shown up to 40 cm (16 inches) out of position relative to other lines within 60 metres (185 feet) of it. For a "1:2500 scale Overhaul" map the comparable relative accuracy of the lines on the map is 1.2 metres (4 feet) relative to other lines within 200 metres (656 feet). I have found that a few of the lines on some maps are much further out of position than this.

The inevitable consequence of these map accuracies, and taking into account the general boundaries rule, is that the line on the map identifies the physical feature to which the boundary is related, and it is the position of the actual feature on the ground - not the position of the line on the map - that is important in determining the position of the boundary. Even then, the line on the map may not be the actual boundary.

Further complications can arise because Ordnance Survey maps use the same line symbol for a wall, fence, hedge, bank, ditch and stream, making it sometimes difficult to know just what the line represents. Worse, if two linear features are parallel and very close there is sometimes not enough room on the map to show both of them: it is sometimes unclear as to which of the features on the ground is the line shown on the map.

What you should do
If you have difficulty in relating the map to what is on the ground, ask HM Land Registry for their opinion. If that does not resolve the matter, consult a chartered land surveyor (e-mail me) .

.This page was last updated on 09 March 2002

 

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The information given on this web site is of necessity of a very general nature and cannot be relied upon to meet your specific requirements. Jon Maynard FRICS cannot be held responsible for any action that may or may not be taken by anyone who accesses this site and acts upon any information found within. Whilst I hope that you may gain benefit from the information in this site, my liability can only extend to specific advice given by me after completion of a formal engagement letter.