Checks with Chart

“Checks with chart!” A phrase commonly heard aboard US Navy submarines. It was (and still is) used by the Quartermaster of the Watch (QMOW), A-Nav, Nav, and Officer of the Deck when performing ship's navigation duties, but has also become a common, smart-alec slang phrase elsewhere on the boat.

 

When transiting at sea, the modern, nuclear-powered submarine spends most of its time submerged at depth. As such, accurately determining the submarine's location is important not only for navigation, but also for ship's safety. Several tools are used by the navigation party to determine and check ship's position; I will discuss two of them. The first is the inertial navigator. This complex and finely tuned electronic instrument senses accelerations and calculates the ship's velocity and heading, and given a known starting point, current position. Using this information, the QMOW plots the calculated ship's position on the navigation chart at set intervals and then checks this position using dead reckoning (which we won't discuss here) and the fathometer. The fathometer is an instrument that measures the depth of water under the keel. This is an important check on the navigation solution. Navigation charts show water depth in fathoms almost identically to how topographical maps show elevation. When the QMOW plots the navigation solution on the chart, he also takes a reading from the fathometer. If at the plotted ship's position on the chart it shows the current water depth is 600 fathoms, and the fathometer also measured the water depth at 600 fathoms, then ship's calculated position “checks with chart”. However, if the plotted ships position shows water depth at 600 fathoms, but the fathometer only measured 400 fathoms, the ship's calculated position “does not check with chart”, and immediate actions to determine ship's position are taken.

 

Elsewhere on the boat, the phrase has become a smart-alec and cynical slang phrase used in various situations. For example, let's say you are standing watch and the guy who is to relieve you has a reputation of being flaky and not very punctual. When the time comes for watch relief and your relief doesn't show up on time, and you find out he was still in the rack, you'd probably tell your fellow watchstanders that it “checks with chart!” Another example for a situation not on a submarine would be you are driving in moderate traffic and you see a BWM driving aggressively, cutting people off, etc. BMW drivers (correctly or not) have the reputation of driving like jerks, so you may utter “checks with chart!” based on your current observations.

To get your own Checks with Chart morale patch, go here. 

 


Comments on this post (1 comment)

  • David Sneed says...

    Very interesting reading…… Good to know. As far as you are concerned, the professionalism of this web-sight Checks with Chart…… Bring me some when you come home with my BMW – I will pay

    On January 01, 2015

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