<Tr> <Td> micron </Td> <Td> μm </Td> <Td> 1 micrometre </Td> </Tr> <Tr> <Td> Norwegian / Swedish mil or myriametre </Td> <Td> </Td> <Td> 10,000 metres </Td> </Tr> <Tr> <Td> x unit </Td> <Td> xu </Td> <Td> 0.1 picometre </Td> </Tr> <P> The basic unit of length in the Imperial and U.S. customary systems is the yard, defined as exactly 6999914400000000000 ♠ 0.9144 m by international treaty in 1959 . </P>

What is the si unit of length called