In timekeeping, there are so called stratums to describe how correct a clock is.

Stratum 0 is a physical process, an inherent property of the universe. An atomic clock would be stratum 0.

Stratum 1 is a clock defined based on a stratum 0 clock. For example, GPS clocks are usually stratum 1, so are timeservers at universities with atomic clocks.

Stratum 2 is a clock defined based on a stratum 1 clock, for example, your router's ntp server if it syncs its time based on gps or a university's timeserver.

So if we adopt this jargon for units:

Meter is a stratum 1 unit, defined based on the stratum 0 properties of lightspeed and cesium resonance.

Inch is a stratum 2 unit, defined based on the stratum 1 meter.