GNSS mean sea level

IoT Modules GNSS Module
1

Hello,

With some colleagues we are using a L86 GNSS module. From the GGA standard message we are getting the altitude above the mean sea level. I wanted to know if the mean sea level is a fixed reference or does it evolve with time?
Thank in advance for your answer.
Regards,

Xavier

2

Hi Xavier,

GNSS module outputs LLA(lat,lon,alt) in WGS-84(World Geodetic Coordinate System 1984) coordinate. It bases on an ellipsoid which related to the earth ground. That means GGA altitude doesn’t relate to sea level or tide.

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Best regards.

3

Hi Raphael,

Thank you for your answer. I got the point that you were using the WGS84 reference ellipsoid.

But you also defined a mean sea level which deviate from this ellipsoid to represent the geoid. And I wanted to know if this geoid you use is time varying or constant, and where does it come from?

Thank you in advance for your answer.
Regards,

Xavier