November 1, 2015

The revival of the sextant in the age of computers and GPS

LA Times - Celestial navigation involves mastery of the sextant, similar to this one that belonged to Charles Darwin. The U.S. Naval Academy is reviving its program teaching the navigational technique. 

Officials reinstated brief lessons in celestial navigation this year, nearly two decades after the full class was determined outdated and cut from the curriculum. That decision, in the late 1990s, made national news and caused a stir among the old guard of navigators.

Maritime nostalgia, however, isn't behind the return.

Rather, it's the escalating threat of cyberattacks that has led the Navy to dust off its tools to measure the angles of stars.

After all, you can't hack a sextant.

"We went away from celestial navigation because computers are great," said Lt. Cmdr. Ryan Rogers, the deputy chairman of the academy's department of seamanship and navigation. "The problem is," he added, "there's no backup." We went away from celestial navigation because computers are great. The problem is, there's no backup. - Lt. Cmdr. Ryan Rogers, U.S. Naval Academy department of seamanship and navigation

Your editor was operations officer and navigator aboard a Coast Guard cutter in the 1960s. Here are some notes on navigation in that period

Sam Smith - Behind the formal hierarchy of rank lay the equally important hierarchy of competence and experience. By the time I got to the cutter Spar, I understood this. I was coming aboard a ship as navigator with only sailing experience and 13 weeks in OCS behind me. I was to lead men who knew much more than I did.

My first test was on the bridge. The captain suggested I take a navigational fix. For piloting fixes, one sighted three shore based (and charted) objects using sextants held horizontally or the peloruses on either wing of the bridge. Peloruses were compasses on a stand with telescopes mounted on top so one could read the bearing and see the object at the same time. Once having read the bearings, you stepped into the pilot house and with a parallel rule transferred the data to the chart. If all went well, your three bearings met in a point or tiny triangle at the exact position of the ship. If all did not go well, such as one of the bearings being off, you were left with a bloated triangle and a far vaguer idea as to where you were.

My first triangle was considerably larger than desired. Beside me was my first class quartermaster, Bill Miller, a QM2, and a seaman assigned to my department. I couldn't really see, but I felt the executive officer and the captain looking over my shoulder as well. I kept my eyes glued on the chart without saying a word, thinking desperately what to do next. The holy spirit put the right words in my mouth. I turned to Miller, shrugged, and said, "Not bad for a fucking reserve, huh?" I could tell from the reaction that I had passed the test -- which was not, after all, to prove how good I was, but to admit that I wasn't....

We set buoys using this same primitive system of navigation. We would have three objects for which we knew their proper angle at the charted location of a buoy. One crew member would stand on the starboard wing of the bridge reporting the changing angle of the right two and another sailor would do the same for left two on the port wing of the bridge.

By their nature, buoys are frequently near bad water. The Aids to Navigation Manual blandly stated that a buoy tender skipper is often called to go "where no ordinarily prudent navigator would take his ship." A prudent navigator, for example, doesn't let his ship get within a hundred feet of a rock that could slice his hull, but marking that rock for other mariners might require that one do just that.

Captain Jimmie H. Hobaugh, who had commanded the Woodrush, a 180-footer in the Great Lakes, told an interviewer, "I used to put her aground all the time - that's the only way you can set some of the buoys that you work. . . If you work Sand Point Bouy in Munising there is the actual imprint of the bow of a 180 in the sand. When you go aground, you drop the buoy and you know it's on station."

We ran aground three times when I was aboard, a fact that amazed my Navy buddies. In the Navy, running aground tends to end one's career. But the Navy doesn't set buoys in the Cape Canal entrance channel where the charts call for a string of markers at the precise edge of a dredge path or right next to a dangerous ledge off Block Island.

...Among our ancillary duties was to rotate the crew on the Nantucket Life Vessel and refuel the ship as we sat moored behind it....The most exciting experience I had with the Nantucket light vessel was when its radar and loran went out and it was dragged off station. My job as navigator was to put the Nantucket back where she belonged. This was before GPS told you how far it was to the nearest Starbucks and my only tools were our radar, loran and the radiotelephone. While it was easy to set one's own course with a radar, telling another ship that was just a spot the screen how to get where it wanted was considerably trickier. But in a manner I couldn't possible reproduce today, we pulled it off.

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