altitudescale

Altitudescale is a term used to describe either a measurement scale for height or an instrument display that conveys vertical position relative to a reference datum. In geodesy and cartography, altitude scales quantify elevation values for terrain or objects, typically expressed in meters or feet and anchored to a datum such as mean sea level (orthometric height) or the ellipsoid (ellipsoidal height).

In aviation, an altitudescale commonly appears as an instrument reading on a barometric altimeter, which estimates altitude based on atmospheric pressure. The scale can be set to different references, including QNH (altitude above mean sea level), QFE (above aerodrome level), or standard pressure. Radio altimeters provide altitude above ground and have their own scale. Altitude scales are critical for airspace separation and instrument approach procedures, and pilots must manage calibration and reference settings to maintain accuracy.

In cartography and geographic information systems, altitude scales are used on topographic maps to indicate elevation via contour lines, color relief, or digital terrain models. The scale defines contour intervals and vertical exaggeration, with elevations annotated in meters or feet. Data quality, vertical datum, and unit consistency affect interpretability and comparability across datasets.

In surveying and geodesy, altitude scales rely on vertical datums and height definitions, distinguishing orthometric (height above the geoid) from ellipsoidal height, and requiring transformations between datums for cross-system compatibility.

In digital tools, altitude scales appear in 3D models, flight simulators, GPS devices, and mapping software, often in dynamic formats that update with location and context. Key considerations include units, datum alignment, measurement accuracy, and calibration for temperature and pressure effects in pressure-based systems.