What features are held as topographic lines but do not form topographic areas?
In OS MasterMap® Topography Layer, wherever topographic line features enclose a region of space, that region will contain a topographic area feature, giving the classification of that region. The geometry of the topographic area feature polygons is the same as that of the topographic line features that bound the polygons. Topographic line features that do not bound polygons are not represented in topographic area feature geometry. For example, a stream represented by a topographic line feature that ends in the middle of a topographic area feature will not be visible if only the topographic area features are displayed. In addition, topographic line features carry important attribute information that is not present in the topographic area features they bound. For example, the geometry of a field is apparent in the topographic area feature, but to know whether one side of the field is bounded by a stream, an obstructing feature or a building requires the bounding topographic line feature.
