I use two devices when flying: an Ipad Mini 2 (cellular) and a Samsung J5 2016. I realized flying over the coast, that the value indicated in the Samsung was always correct, as it was close the the one of the Altimeter, less than 20 ft different. On the other side, with the Ipad, the level of error was at the same time of 300 ft, and was not stable, it could change strongly in some minutes. The Samsung uses GPS+GLONASS.  and the Ipad only GPS. Does somebody know why the measure of the Samsung is better ? is the addition of GLONASS ?  or there is another reason ?

Multi-constellation receivers can get a much more accurate fix in all four dimensions (lat, long, height and time). In addition, most multi-constellation receivers also receive SBAS (EGNOS or WAAS) which further improves their accuracy, especially their height accuracy.

Finally‌‌, it is possible to optimise any GNSS receiver for 1D, 2D, 3D or 4D operation - most non-SBAS receivers are optimised for time (1D) or surface navigation (lat/long, 2D). Only SBAS-capable receivers are usually optimised for 3D or 4D navigation.

+x

T67M - 11/8/2017 6:15:20 PM

Multi-constellation receivers can get a much more accurate fix in all four dimensions (lat, long, height and time). In addition, most multi-constellation receivers also receive SBAS (EGNOS or WAAS) which further improves their accuracy, especially their height accuracy.

Finally‌‌, it is possible to optimise any GNSS receiver for 1D, 2D, 3D or 4D operation - most non-SBAS receivers are optimised for time (1D) or surface navigation (lat/long, 2D). Only SBAS-capable receivers are usually optimised for 3D or 4D navigation.

Thanks for the clarification. This confirms that getting the information of elevation, as suggested in the Forum about suggestions for improvements, would be really important, relying on the altimeter information plus the elevation one, that is very precise in the planning mode of SD, a quick mental calculation will provide the height.