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The importance of correct scale in application maps
A note by GLPG

Revised May 2013

The Regulations attached to the Wildlife & Countryside Act 1981 require applications for changes to the Definitive Map to be accompanied by a map drawn to a scale of not less than 1:25,000, showing the way or ways to which the application relates.  Some authorities have taken the view that enlargement, either by computer zooming or photo-enlargement, brings the map to an acceptable scale.  That is of course nonsense, as is the argument that a map stored digitally on computer does not embody a scale until the product scale is chosen.  Every map is created to a scale, and the detail varies accordingly. That detail can be vital in rights of way determinations. For example, Ordnance Survey 1:25,000 Explorer maps show field boundaries, whereas 1:50,000 Landranger maps do not; and it may be vital to show on which side of a field boundary a particular right of way runs. A 1:50,000 Landranger map blown up to 1:25,000 will still have no field boundaries.

In the Winchester appeal, it was held that to qualify for exemption from extinguishment of public vehicular rights, the 1981 Act requirements must be strictly applied unless they involved trivialities, known as de minimis.  Defra at one stage thought the map scale issue was de minimis but agreed to change its views. That was helped by the judgment in Maroudas v SoSEFRA and Oxfordshire CC [2009] EWHC 628 (Admin) (see http://www.bailii.org/ew/cases/EWHC/Admin/2009/628.html) which considers the application of the de minimis principle in some detail.

For confirmation of the computer storage aspect, GLPG sought the help of the OS which replied in these terms:

1.   Digital map data is supplied to users, and stored in computer systems, in electronic form (which may be thought of in simple terms as collections of binary digits). These “digits” are arranged in ‘records’ and ‘fields’ within the dataset, representing the various features, lines, points, names, etc. of the source map or survey. Information not represented within the data cannot be generated by the computer.  The computer programmes within digital mapping and Geographical Information Systems re-interpret this electronic data to display an image of all or parts of the source map.

2.   Digital mapping systems enable the map data held within the system to be displayed at a wide range of enlarged or reduced scales. However the content of the presented map image remains limited to that of the source data from which the image is presented.  Regardless of the scale at which a plot from digital map data is presented, the content and accuracy specifications of that plot can be no more detailed or accurate that the information contained within the source data held within the computer at that time.

3.    Content resolution and the degree of planimetric fidelity of the content shown (whether the content is accurately surveyed and represented, or cartographically generalised), are determined by the nominal scale of the mapping. Mapping re-presented at an enlarged scale will retain the content resolution and portrayal of the smaller scale. It will not acquire the geometric fidelity or level of detail of a map ‘surveyed’ at a larger scale. Hence presenting map data with (say) a 1:50,000 scale specification, enlarged to (say) 1:25,000 scale, will not alter either the content specification or the accuracy of the presented data. If a plot is required containing the map content resolution, geometric fidelity and positional accuracy specification of (say) a 1:25,000 scale OS Explorer Map, or a 1;10,000 scale OS LandPlan, then the richer content and higher accuracy of source data related to those scales of mapping will be required.

GLPG said the same thing in fewer words! Buckinghamshire CC saw the light in respect of photographic enlargements, as did an inspector. Dorset CC officers refused for a long time to see the light regarding computer zooming, but eventually the intervention of the Head of Legal Services brought sanity to bear. Outstanding claims were rejected and a policy decision made to pursue the opposition in pipeline cases.  That decision was challenged in the High Court in the case of TRF v Dorset CC (Oct 2012) – http://www.bailii.org/ew/cases/EWHC/Admin/2012/2634.html- in which it was decided that the map scale requirement was mandatory and that using an enlarged smaller scale was of sufficient importance to defeat the claims and lose motor vehicle rights. The decision was however overturned in the Court of Appeal on 20 May 2013 – see http://www.bailii.org/ew/cases/EWCA/Civ/2013/553.html . The decision is curious in that the court took a view as to what ‘drawn scale’ means that is the opposite of the view reported by the OS which had been consulted by the TRF to give expert evidence.  The court also subscribed to an interpretation of the governing legislation which renders it meaningless.  The way currently remains open to seek leave from the Supreme Court to appeal.