AltitudeAccuracy

AltitudeAccuracy is a geolocation attribute that indicates the estimated uncertainty of the altitude value for a reported position. In web and mobile location APIs, it is provided as altitudeAccuracy, measured in meters, and applies to the altitude component of the position. The corresponding altitude is typically given as height above the reference ellipsoid (geodetic height); altitudeAccuracy may be null if the device cannot determine vertical error.

In practice, altitudeAccuracy is often interpreted as the vertical uncertainty of the altitude measurement, commonly viewed as a one-sigma (standard deviation) bound. However, the terminology and interpretation can vary by implementation, so the exact confidence level is not uniformly defined across platforms.

Altitude data can come from different sensors, notably GPS, barometers, and sensor fusion systems. Barometric altitude, in particular, is sensitive to changes in local atmospheric pressure and weather, which can affect accuracy. Because vertical measurements are usually less precise than horizontal ones, altitudeAccuracy can be larger or more variable depending on environment and sensor availability.

Usage and implications: altitudeAccuracy helps applications assess the reliability of the vertical component when presenting 3D maps, conducting navigation with altitude information, or delivering augmented reality experiences. It is important to use altitudeAccuracy together with horizontal accuracy and other metadata to evaluate overall position quality. If altitude is unavailable, altitudeAccuracy is typically null, reflecting the absence of vertical uncertainty data.