![Taiwan, Province of China[a]](https://files.upgates.com/graphics/countries/tw.svg "Taiwan, Province of China[a]"){kind=small}
Scale Ruller 6 in 1 is one of the most important tools for navigation.
Its use significantly reduces probability of random errors in the calculations.
The ruler has a total of 6 different scales, which are positioned on both sides.
- Side A: kilometres and Nautical Miles for charts in scale 1:500 000 and 1:250 000
- Side B: kilometres and Nautical Miles for charts in scale 1:200 000, inches and centimetres
