Editing Depth gauge (section)

== Mode of operation ==
With water depth, the ambient pressure increases 1 [[bar (unit)|bar]] for every 10 m in fresh water at 4&nbsp;°C. Therefore, the depth can be determined by measuring the pressure and comparing it to the pressure at the surface. Atmospheric pressure varies with altitude and weather, and for accuracy the depth gauge should be calibrated to correct for local atmospheric pressure. This can be important for decompression safety at altitude. Water density varies with temperature and salinity, so for an accurate depth measurement by this method, the temperature and salinity profiles must be known. These are easily measured, but must be measured directly.