When you maneuver a ship, there are controllable forces, such as propeller and rudder effects. There are also uncontrollable forces, such as wind, current, sea conditions. Moreover, each vessel has different characteristics and reacts differently. You have also to take into account the characteristics of your ship that may not be constant and given, such as ship loading and hull conditions. As a result, a captain works in an environment where a ship's behavior is not observed in exactly the same way and each situation is different from another. A maneuver is a dynamic process. You have your plan and when you execute it, you want to have a continuous update to understand the effect that your order has achieved and the next course of action in order to be able to follow your plan. Each time you find yourself in situations where your ship reacts differently due to everchanging combinations of speed, rudder, wind, current, sea state.

You need to be adaptable to the environment. Often, a too frequent assessment of your orders is not good because you need some time to let the ship react to your order because of its inertia. At the same time, if your feedback cycle is too slow, you might not have enough time to correct your action. You might end up not being able to follow your plan any more. In that case, the wisest thing you can do is give up and start again the maneuver from scratch instead of trying improbable corrections.

In markets, you do not have controllable forces, but you have expected crowd behaviors. In this context also each situation is different. A trader establishes a plan and during the trade execution, as new data come in, he/she assesses the market's behavior. The frequency at which this feedback process is done is critical. Traders may overreact and be deceived by the short term noise (you need time for the trade to develop), or they may be too slow to realize that the trade is not going as expected. How much data do you need, how often? How is the behavior different from what is expected is an interesting parameter. What is the threshold that makes you realize the trade went wrong? A ship maneuvering characteristics can be modeled mathematically, but in real life captains have to apply their experience and judgment to work in an observe-evaluate-decide-act cycle, which is very similar to what a trader does in a real time environment. Similarly, the market can be modeled, but most of the times expected outcomes require judgment and interpretation. It is all about the human dimension, where the action-effect cycle is matched against broad assessments of a generic "system" behavior.

Jeremy Smith comments:

“Consider how often a vessel must change its course in leaving a harbor, yet once on the high seas a single heading may bear it to its destination. Only
a major navigational hazard could change it.”

 – Louis Auchincloss, The Embezzler [1966]

J.T. Holley adds:

In the spirit of Patrick O'Brian I would have to disagree or at least add to this quote. Pirates, Enemies and Gov't can cause navigational changes in both the ships directions and destinations as well as in the markets. Seamanship by David Dodge is a excellent book that discusses the navigational patterns as well that the U.S. Navy utilizes. Having served onboard the U.S.S. Stark I can assure you that rarely is "a single heading" utilized to reach a destination. Sure it is the broad direction, but there are other directions that are in between when going from point A to point B.

Pitt T. Maner III writes:

Let me add a nice quote from The New Dictionary of Thoughts (1963). I wish I knew who "Anon" was:

A smooth sea never made a skilful mariner, neither do uninterrupted prosperity and success qualify for usefulness and happiness. The storms of adversity, like those of the ocean, rouse the faculties, and excite the invention, prudence, skill, and fortitude of the voyager. The martyrs of ancient times, in bracing their minds to outward calamities, acquired a loftiness of purpose and a moral heroism worth a lifetime of softness and security. Anon.

The pdf of the book is searchable and many a fine old quote can be found there. 

Jim Sogi adds:

Jeff is right. A sailing ship in particular will sail the best course made good, rather than rhumb line. For example, it will take the best angle to the wind, for the ship best speed, even though off rhumb line, for best course made good. A catamaran, for example, will go faster tacking down wind, zig zagging rather than shortest distance. I think day traders know this instinctively. It's quantified in markets in the absolute volatility numbers, or in Sharpe result numbers.

Another curious effect is when there is a strong current setting the vessel down. The vessel aims at a different point than where it intends to go, and 'crabs' along its course. This is hard for people to understand, as they can't really see the current, but one has to be aware of the motion of the ship in relation to the course, which is a derivative function. I suppose this might be thought of as Sharpe as opposed to gross dollars in trading or percent.

Another odd effect I experienced last weekend up in Alaska skiing was during a white out, a sense of vertigo. There is no visual reference point to balance, and its easy to lose balance in total white out conditions. While standing still, a small avalanche passed by, and though I was standing still, seeing the snow pass by gave the impression of motion, and threw me off balance. Or there is the feeling of standing still, then all of a sudden hit a bump and realize the skier was moving, but couldn't see it. The idea is that sometimes the perception is not correct and some other reference is needed. Pilots know this. This was one of the main points in survival. Loss of a reference point often lead to panic and death. In the markets, it's easy to lose reference. Chair's international numbers, I believe, are an attempt to get some sort of reference point. I had guides skiing up in the wilderness, who have a lifetime of experience and reference. Like markets, if you lose your reference point, you'll be dead in short order. 





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