# Administrative boundary alignments

Administrative boundaries may or may not have a predefined relationship with topographic features in their locality. This relationship is known as a 'boundary mereing' and is recorded within OS MasterMap as a textual description. A list of the most common abbreviations is given in the following table:

## Common abbreviations for boundary mereings in OS MasterMap Topography Layer.

| Object or mereing                                                                               | Abbreviation |
| ----------------------------------------------------------------------------------------------- | ------------ |
| Baulk, bank, base of, basin, bridge, broad                                                      | B            |
| Cam, canal, causeway, centre of, channel, cliff, conduit, cop, course of, covered, culvert, cut | C            |
| Dam, ditch, dock, double, down, drain                                                           | D            |
| Double ditch or drain                                                                           | DD           |
| Double fence                                                                                    | DF           |
| Defaced                                                                                         | Def          |
| Edge of, eyot                                                                                   | E            |
| Face of, fence, fleet, freeboard                                                                | F            |
| Feet                                                                                            | ft           |
| Harbour, hedge                                                                                  | H            |
| Inches                                                                                          | Ins          |
| Kerb                                                                                            | K            |
| Lade, lake, lead, loch, lockspit, lynchet                                                       | L            |
| Marsh, mere, moat                                                                               | M            |
| Mean high water                                                                                 | MHW          |
| Mean high water springs (Scotland only)                                                         | MHWS         |
| Mean low water                                                                                  | MLW          |
| Mean low water springs (Scotland only)                                                          | MLWS         |
| Metres                                                                                          | M            |
| Old                                                                                             | O            |
| Passage, path, pond, post                                                                       | P            |
| Race, railway, ride, river, road, root of                                                       | R            |
| Root of hedge                                                                                   | RH           |
| Scar, sewer, side of, slope, sluice, stone, stream                                              | S            |
| Top of                                                                                          | T            |
| Track                                                                                           | Tk           |
| Undefined                                                                                       | Und          |
| Wall, weir                                                                                      | W            |

The following table contains examples of combined abbreviations:

## Combined abbreviations for boundary mereings in OS MasterMap Topography Layer.

| Object or mereing                             | Abbreviation |
| --------------------------------------------- | ------------ |
| Centre of bank, basin, baulk, broad and so on | CB           |
| Centre of railway, river, road and so on      | CR           |
| Centre of old course of stream                | COCS         |
| 1.22metres root of hedge                      | 1.22 m RH    |

{% hint style="info" %}
*Special rules apply to boundary mereings, and only the more common ones are listed.*
{% endhint %}

Where the mereing relationship of any boundary alignment changes or where a boundary changes from one side of a real-world object to another, the point of change is shown by a boundary half-mereing change symbol, usually in opposing pairs. The location of the boundary half-mereing symbol is coincident with the boundary alignment and not the feature to which it is mered.


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