Naval Gaming Introduction

The terms defined here are consistent with the usage in the United States Navy during the 1960s and 1970s. None of the definitions are "official" in any way. They are listed here to help explain their usage on the other pages of this site.

Base Course	The course or direction in which a formation is to proceed. Individual ships within a formation may or may not steam in this direction.
Bearing	A direction from one ship to another. Bearing is normally expressed in degrees from 000 to 359.
True Bearing	A bearing measured with reference to true north as 000.
Magnetic Bearing	A bearing measured with reference to magnetic north as 000.
Relative Bearing	A bearing measured with reference to the bow of the ship as 000.
Expressing Bearings	Bearings are always expressed as a three digit number, with leading zeroes as required. North is 000; South is 180; East is 090; and West is 270. Unless otherwise stated, all bearings are true bearings. Contrary to what is shown in 90% of all movies, proper naval usage never includes "degrees" with a bearing value, and the numbers are always spoken individually (ex. "Sir, the enemy bears zero five six." "Buoy bears three five zero, relative.").
Change of Front	Any maneuver in which a formation changes its base course and the axis of the formation (i.e., the entire formation is pointed in a new direction). Also known as a wheel.
Course	The direction of travel of a ship or formation.
Base Course	The direction in which a ship or formation is to travel. This may or may not be the actual course of a ship or formation at any given moment.
Reciprocal Course	The reverse or opposite of a course. To determine a reciprocal course, either add or subtract 180 so that the result is from 000 to 359, inclusive.
Disposition	An ordered arrangement of two or more formations.
Distance	The distance or range between ships within a formation. The distance is usually determined by the size of ships within a formation. Preferred distances vary by individual navy and at different times. Typical (1930s) battle line distance was 700 to 1,000 yards. U.S. Navy standards (c. 1975) were:   Cruisers and larger, large amphibious, logistic ships 1,000 yards Destroyers, submarines, smaller amphibious ships 500 yards Other small ships 300 yards
Evolution	A set of maneuvers to change one formation into another.
Formation	An ordered arrangement of ships and/or units (groups of ships).
Formation Turn	An evolution in which an entire formation changes to a new course. When the evolution is complete the ships in the formation have the same relative relationship to each other, but the formation is moving in a new direction.
Guide	A ship within a formation which the other ships use as a reference. The guide is always assumed to be in its correct position within a formation. A guide is assigned by the OTC, or by certain maneuvers. The guide is designated by the Golf flag (i.e., the guide ships flies the Golf flag to indicate that it is the guide).
Interval	The distance or range between formations.
Maneuvering Interval	Distance between formations within a disposition. Determined by multiplying the distance by the number of ships in the longest formation.
Extended Maneuvering   Interval	Maneuvering Interval plus 500 yards.
Large Ship	A ship larger than a destroyer (since the 1980s the growth in the size of destroyers makes them Large Ships also).
Main Body	A unit or group of units which constitutes the part of a formation or disposition which is to be protected.
Maneuver	A change of course, speed, or formation, or a combination of these changes to adjust a ship's position within a formation.
Officer in Tactical Command	See OTC.
OTC	Officer in Tactical Command. The officer who is assigned to issue orders to a group of ships. This may be the senior officer present, or may be another officer designated by the senior officer.
Port	The left or to the left side of a ship, as one faces forward on the ship.
Points (Compass)	The Points of the Compass are a traditional method for indicating direction. The system of Points divides the compass into 32 named directions. The Cardinal Points (North, South, East, and West) are set 90° apart. The Intercardinal Points (Northeast, Southeast, Southwest, and Northwest) divide the Cardinal Points in half. Quarter Points divide the Intercardinal points in half, and then in half again, giving a gradation in units of 11-1/4 degrees. While this refinement of direction was quite adequate for sailing ships, the ability of steam powered ships to sail on any heading effectively eliminated the need for expressing direction in Points. Only the Cardinal and Intercardinal points are commonly used today.
Screen	An arrangement of ships, usually smaller than those in the main body, intended to protect the main body. There are many types of screens, each with its own organizations, objectives, and functions. These include scouting screens, anti-submarine screens, anti-aircraft screens, and radar picket screens.
Sector	Similar to a station, but allowing a ship to be anywhere within a designated area. Sectors never overlap.
Simultaneous Turn	A turn in which all ships in a formation execute a turn at the same moment.
Small Ship	A ship of destroyer size or smaller. See also Large Ship.
Senior Officer Present Afloat	See SOPA.
SOPA	Senior Officer Present Afloat. The most senior naval line officer in a group of ships.
Starboard	The right or to the right side of a ship, as one faces forward on the ship.
Station	An exact assigned position of a vessel within a formation. Stations are defined with reference to the guide for line formations and with reference to the formation center for circular formations.
Tactical Diameter	The diameter of the semi-circle created when a ship puts its rudder over at any constant angle.
Standard Diamater	Standard Tactical Diameter defines the tactical diameter used by a formation. This is determined by the size of ship in the formation. When maneuvering, all ships in a formation use rudder angles such that they all turn with the same Standard Tactical Diameter. U.S. Navy standards (c. 1970):   Largest Ship Present Diameter Aircraft carrier 2,000 yards 1 or more cruiser or large destroyer or larger ship  1,200 yards Max 1 cruiser size 1,000 yards Only smaller ships 800 yards
Reduced Diamater	Reduced Tactical Diameter is the minimum tactical diameter used by ships in a formation when executing an emergency turn. Typically this is the tightest tactical diameter of the least maneuverable ship in the formation.
Threat Axis	The direction from which a formation or disposition is threatened, that is, the direction from which an attack is most likely. There may be more than one threat axis relative to a formation. Threats may be from surface, subsurface, and air. These threat axis may be from different directions simultaneously.
Turn Together	A Simultaneous Turn (see above).
Wheel	A Formation Turn (see above).
Unit	One ship, or a group of small ships maneuvering together.
Wheel	A maneuver in which a line changes front by swinging in an arc as with the turning of a spoke in a wheel. Also known as a change of front.