A spot elevation is a point on a map or chart that has its elevation noted, usually in terms of vertical distance from sea level. Spot elevations are a common feature of topographic maps. Topographic maps show both the geography of an area and physical features of the terrain.
Most of the time, elevation is indicated on a topographic map by concentric lines that follow the contours of the terrain. Lines that are enclosed by many other lines are further away from sea level. Spot elevations are used for particularly notable features, like mountain peaks or road junctions. They are usually indicated by an "X," with the elevation next to them in numerals. Benchmarks are a special kind of spot elevation. They are points that have been surveyed as accurately as possible to serve as references for the rest of the terrain. Benchmarks are indicated by the abbreviation "B.M."