A land lighthouse is simply a lighthouse

Lighthouse

A lighthouse is a tower, building, or other type of structure designed to emit light from a system of lamps and lenses or, in older times, from a fire, and used as an aid to navigation for maritime pilots at sea or on inland waterways....

 constructed to aid navigation over land, rather than water. Historically, they were constructed in areas of flatland where the featureless landscape and prevailing weather conditions (e.g. winter fog

Fog

Fog is a collection of water droplets or ice crystals suspended in the air at or near the Earth's surface. While fog is a type of stratus cloud, the term "fog" is typically distinguished from the more generic term "cloud" in that fog is low-lying, and the moisture in the fog is often generated...

) might cause travellers to become easily disorientated and lost. In such a landscape a high tower with a bright lantern could be visible for many miles.

One example of such a structure is Dunston Pillar

Dunston Pillar

Dunston Pillar is a grade II listed stone tower in Lincolnshire, England and a former 'land lighthouse'. It stands beside the A15 road approximately south of Lincoln near the junction of the B1178 , in the village of Dunston....

, an 18th century tower built to help travellers crossing the heathland of mid-Lincolnshire

Lincolnshire

Lincolnshire is a county in the east of England. It borders Norfolk to the south east, Cambridgeshire to the south, Rutland to the south west, Leicestershire and Nottinghamshire to the west, South Yorkshire to the north west, and the East Riding of Yorkshire to the north. It also borders...

 and to lessen the danger to them from highwaymen.

Due to general improvements in transport and navigation throughout the 19th century, land lighthouses became almost totally obsolete as aids to travellers in remote places.