

I can kinda see how, if one were inventing a system of measurements, relatability might be important.
However, predictable units, magnitudes, and relations between scales like distance, volume, and weight is also important.
I guess the two attributes relatability and predictability could be seen to oppose each other?
I mean a “barrel of water” is easier to imagine than 100L of water, but only if barrels are an object you’re familiar with.
However, the predictability of the metric system allows you to imagine a container with a volume of 100L even if no such container really exists.




Fair enough.
In the metric system this is isn’t really a problem because the math is much easier to start with.
1 hectare is 10,000 m2, so a depth of 1m over 1 hectare is 10,000m3, or a depth of 1cm is 10,000m3 / 100 = 100m3.