Contact Evaluation Plot

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The Contact Evaluation Plot (CEP) is the representation of sound bearings (e.g. due to cavitation , propulsion, active sonar) usually from vehicles and is mainly used to create a surface picture of the situation on submerged submarines. The sound bearings are continuously recorded in a coordinate system over time ( y-axis ) in a typically 360 ° sector ( x-axis ) and thus generate sound traces that provide information about the movement of the noise carriers.

Terms

True bearing and side bearing

The true bearing (Bmn) describes the bearing of an object from one's own location relative to true north, ie based on the north direction according to a compass. The bearing is always given as three digits without a degree symbol (001 - 360).

The lateral bearing (Bm) always indicates a bearing relative to your own course line (Ke) and is indicated with degree symbols. It can be between 0 ° (right ahead) and 180 ° (right astern) and has a negative sign on the port side (left side) and a positive sign on the starboard side (right side).

Formula : Bmn = Ke + Bm

Example : We drive 010 and take a bearing on the port side at 100 °. The vehicle is correctly bearing in 010 + (-100 °) = -90 = 360 - 90 = 270.

Bearing rate

The bearing rate (BR) or bearing migration per minute and the change in the bearing rate over time are the most important information about a sound trail. A bearing rate is only meaningful in that part of a noise track in which the noise carrier has a constant movement (constant course and constant speed). If the noise trail moves to the left, the sign of the bearing rate is negative, if it moves to the right, the sign is positive.

Example : A vehicle was bearing its bearings at 07:42 in 080, at 07:50 in 060. The vehicle moved 20 ° to the left in 8 minutes, ie it had an average bearing rate of -2.5 ° / min.

Bow and location

The bow indicates the side of a vehicle that can be seen from your own location. With the bow on the right, the bow is on the right side, ie the starboard side of the vehicle can be seen, with the bow on the left the port side can be seen accordingly.

The position (Im) indicates the angle between the vehicle's course line (Kd) and the true bearing (Bmn). The position can be between 0 ° (bow directed directly at your own location) and 180 ° (rear directed directly at your own location). The sign of the position is negative for the left bow and positive for the right bow.

The direction of the position is always given via the bow, except for position 0 and position 180.

Formula : Kd = Bmn +/- 180 ° - Im

Example : A vehicle with course 270 is bearing in 030. The vehicle has a position of 030 + 180 ° - 270 = -60, i.e. bow left, position 60.

Standing bearing

Having a standing bearing to an object means that the object is always on the same bearing, ie does not migrate to the left or right.

A stationary bearing can arise from the fact that a vehicle

  • runs with the same course and the same journey,
  • starts or runs at a higher speed than your own speed,
  • comes towards (exactly from right ahead) or comes up (exactly from right astern),
  • is very far away.

In principle, every stationary bearing is a potential risk of collision if nothing more is known about the vehicle. If there is (intentionally) a stationary bearing to an approaching vehicle, the attached own course is also the fastest intercept course for the vehicle.

Interpretation of the CEP

Change of distance

If the amount of the bearing rate of a noise carrier increases over time, ie the sound track flattens out (runs convex), the noise carrier comes closer (is converging). In the case of an increasingly erecting sound trail (concave), the amount of the bearing rate becomes smaller over time, ie the noise carrier moves away (is running down). In the case of a straight course of the noise track, ie with a very low to no bearing rate, there is a standing bearing to the noise carrier. If a noise trail changes from a convex to a concave course, the noise carrier was in the transition from convex to concave in the Closed Point of Approach (CPA), ie at the point of its closest approach to its own location.

Bug

If a vehicle is on the right-hand side (to starboard) with a negative bearing rate (goes to the left) or a stationary bearing, the vehicle always has bow on the left. A vehicle on the left side (to port) with a positive bearing rate (goes to the right) or a standing bearing always has bow right.