GPS Elevation accuracy

Good day,
I want to create a Land Survey App, that can provide not only lat /Long, but also Elevation. According to my research, it is not possible to get more accurate elevation reading than 10m?
Does anyone know of a better way to get accurate readings?

Thanks in advance


@Johan_Jacobs He is right, in fact through the GPS system it is not possible to have an approximation below 10 meters; even being on the seashore, it is never possible to have 0 altimetric.

If you are lucky enough to get that Johan with a cell phone gps.

There are plenty of articles about why better accuracy/precision is not possible... here are two:

Altitude Accuracy.

Using a GPS with two GPS frequencies improves accuracy by correcting signal distortions caused by Earth's atmosphere.