Use the fathometer to determine whether the depth of water under the keel is sufficient to prevent the ship from grounding and to check the actual water depth with the charted water depth at the fix position. The navigator must compare the charted sounding at every fix position with the fathometer reading and report to the captain any discrepancies. Taking continuous soundings in restricted waters is mandatory.

If the warning sounding is received, then slow the ship, fix the ship's position more frequently, and proceed with extreme caution. Ascertain immediately where the ship is in the channel; if the minimum expected sounding was noted correctly, the warning sounding indicates the vessel may be leaving the channel and standing into shoal water. Notify the vessel's captain and conning officer immediately.

If the danger sounding is received, take immediate action to get the vessel back to deep water. Reverse the engines and stop the vessel's forward movement. Turn in the direction of the deepest water before the vessel loses steerageway. Consider dropping the anchor to prevent the ship from drifting aground. The danger sounding indicates that the ship has left the channel and is standing into immediate danger. It requires immediate corrective action by the ship's conning officer, navigator, and captain to avoid disaster.

Many underwater features are poorly surveyed. If a fathometer trace of a distinct underwater feature can be obtained along with accurate position information, send the fathometer trace and related navigational data to NIMA for entry into the Digital Bathymetric Data Base.

• Piloting - The Running Fix - 2009-04-22 - 09:00:05
• Stationing the Piloting Team - 2009-04-22 - 05:51:04
• Preparing Charts and Publications - 2009-04-22 - 05:40:22
• Training - Piloting Simulators - 2009-04-13 - 08:32:52
• Piloting - Finding Compass Error by Trial and Error - 2009-04-13 - 08:20:42
• Minimizing Errors with a Two Bearing Plot - 2009-04-13 - 08:14:39
• Minimizing errors in piloting - Common Errors - 2009-04-13 - 07:54:54
• Determining Track Made Good by Plotting Running Fixes - 2009-04-13 - 07:43:05
• Assuming Current Values to Set Safety Margins for Running Fixes - 2009-04-13 - 07:31:45
• Navigational Preparations for Anchoring - 2009-04-13 - 01:15:09

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