To a more actual geoid model: https://play.google.com/store/apps/details?id=tools.gnss.highprecisiongeoid

The principal aim of this app is calculate being offline a high precision geoid height undulation (N) to be used in field by engineers topographers and cartographers who are using a GNSS receiver with high precision coordinates too. The GPS from your phone doesn't give to you a high precision ellipsoidal height so it isn't a good idea use it to obtain the ellipsoidal height (h).

Undulation of the geoid (N) is the mathematical process of determining the height in meters positive if above or negative if below relative from the geoid to a ellipsoid provided by the GNSS system. The height given by you GNSS receiver it's referred to a specific GNSS ellipsoid like WGS84 and is called ellipsoidal height (h).

The best approximation for your topographic height it's called orthometric height(H) obtained by the formula: H = h - N.


This app calculate Geoid Undulation using EGM96 15' x 15' grid http://earth-info.nga.mil/GandG/wgs84/gravitymod/egm96/intpt.html interpolating it with CSPLINES Piecewise Bi-interpolator from Apache Commons Math 3.6.

This can be used as free version of more precision EGM2008 2.5'x2.5' grid found at https://play.google.com/store/apps/details?id=tools.gnss.highprecisiongeoid

It's works offline so you don't need be connected to use it.
It's only needed be connected to download it from play store.