A definitive map is a map prepared by a surveying authority which is a legal record of the public's rights of way in one of four categories (footpath, bridleway, road used as a public path or byway open to all traffic). If a way is shown on the map, then that is legal, or conclusive, evidence that the public had those rights along the way at the relevant date of the map (and has them still, unless there has been a legally authorised change). But the reverse is not true. So the showing of a way as a footpath does not prove that there are not, for example, additional unrecorded rights for horseriders to use the way. Nor is the fact that a way is not shown at all on the definitive map proof that the public has no rights over it.
The definitive map is therefore useful in providing evidence of the public's rights, but may not tell the whole story. A check should be made with the surveying authority to see if it has reason to believe that there are additional rights, as yet unrecorded, over any particular area of land. This can be especially important if the land is for sale or is the subject of a planning application for development.
Definitive maps have to be compiled for all of England (and Wales) except the 12 inner London boroughs.