Sea level refers to the average height of the sea surface.
Sea level is the datum against which land elevation and sea depth are measured. Mean sea level (MSL) is the average of high and low tides. Due to variations in Earth's gravity field,
ocean circulation, climate, winds, and other factors, sea level is not constant everywhere on the Earth. Sea level rise may be an important indicator of climate change.
Microwave/radar (1-100 GHz)
Other sources for data