Note that the MSL model is a gridded EGM96 geoid

[drf5n]

Here the code has a couple references to the MSL model:

SparkFun_u-blox_GNSS_Arduino_Library/src/SparkFun_u-blox_GNSS_Arduino_Library.cpp

Lines 17402 to 17405 in 2ae7289

	// Get the current altitude in mm according to mean sea level
	// Ellipsoid model: https://www.esri.com/news/arcuser/0703/geoid1of3.html
	// Difference between Ellipsoid Model and Mean Sea Level: https://eos-gnss.com/elevation-for-beginners/
	int32_t SFE_UBLOX_GNSS::getAltitudeMSL(uint16_t maxWait)

It should also refer to uBlox at

https://portal.u-blox.com/s/question/0D52p00008HKDSkCAP/what-geoid-model-is-used-and-where-is-this-calculated
...which seems to indicate EGM96 on a 10°x10° grid, interpolated to the location.

Maybe add a line like:

// Geoid: https://cddis.nasa.gov/926/egm96/egm96.html on 10x10 degree grid

[PaulZC]

Hi @drf5n ,

Thanks! We'll add this to the next release.

Best wishes,
Paul