# How-to QINSy Sign Conventions

Within QINSy certain sign conventions are used for object reference frame offsets and attitude angles and rotation offsets.

**Sign Conventions:**

### XYZ Coordinate Offsets

*Coordinate Offsets in the Ship Geometry*

* *

The following symbol is used in the picture above:

This mark signifies the Centre of Gravity (CoG), Centre of Rotation (CR) or the Central Reference Point (RP) of the vessel.

This point has the coordinates X=0, Y=0 and Z=0 in the Ship Geometry.

QINSy computations assume this is the point where there is minimum vertical displacement due to vessel rolling and pitching.

### HPR Attitude Angles

*Attitude Angles in the Ship Geometry*

The following abbreviations are used in the picture above:

**H**

Heading. Drawn is the Positive Rotation to Starboard convention.

All system heading offsets and heading computations in QINSy use the Positive Rotation to Starboard convention.

**P**

Pitch. Drawn is the Positive Bow Up convention for motion sensors.

Other system pitch offsets and all pitch angle computations in QINSy use the Positive Bow Up convention.

**R**

Roll. Drawn is the Positive Heeling to Starboard convention for motion sensors.

Other system roll offsets and roll angle computations in QINSy use the Positive Heeling to Starboard convention.

**Hve**

Heave. Drawn is the Positive Heave Up convention for motion sensors.

Other systems and all height offset computations in QINSy use the Positive Height Up convention.