GPS Elevation

The GPS coordinates contain only 2 pieces of information: latitude and longitude on the terrestrial globe. Altitude (or elevation, or z value) is the height of the point on Earth, relative to the sea level which is counted as the base altitude (0 meters).

Altitude cannot be calculated from coordinates directly.

However, NASA's satellites scoured the Earth's surface with radars and more or less accurately modeled the elevation of each point on the globe. dCode uses this data to find the altitude of a GPS point (reference geoid). dCode uses this data to find the altitude of a GPS point.

NB: The values given take the sea level as an altimetric reference.

Knowing the precise altitude of a house or building is more complex. Specialized tools such as laser altimeters or topographical surveys may be needed to get an accurate measurement of the elevation of a specific building. The height of a house is generally relative to its foundation, add the height of the ground to obtain an absolute altitude.

Altitude/terrain data represents gigabytes of digits, there are several research studies that offer it. SRTM (Shuttle Radar Topography Mission) data, among the most comprehensive on the globe, is available here (link)

GPS altitude is based on measurements made by satellites. Barometric altitude, on the other hand, is measured using an atmospheric pressure sensor built into some altimeters, which uses changes in pressure to estimate altitude. The two methods may provide slightly different results.