Transverse deviation
Lateral deviation ( off course , cross track error , cross track distance , XTE , XTD , XTK ) describes in navigation the distance between the planned route (given by two waypoints) and the actual position. Measurements are taken vertically along the planned route.
theory
A transverse deviation occurs when the direction of flow of the surrounding medium (e.g. air or water) deviates from the direction of action of the propulsion of a vehicle or aircraft so that the flow does not act exactly from the front or the rear.
The mathematical-physical explanation for this lies in the fact that the effect of two force vectors (here: drive and flow) on the same object creates a new total force vector through vector addition. While the total movement of the object follows the total force vector, the transverse deviation results exclusively from the effect of the flow vector. If the flow vector is a constant acting force, the lateral deviation increases linearly over time. There can be significant deviations from the desired course.
In order to avoid an increase in the lateral deviation and to keep it as close as possible to zero, the drive vector must be changed in such a way that the vector resulting from the addition of the drive and flow vector corresponds to the desired heading. This is achieved by subtracting the flow vector from the desired total force vector and obtaining the required drive vector as a result.
Practical implications
In aviation instrument navigation , which is carried out with the help of direction finding transmitters, the destination of the flight is known, so that in a world without wind you only have to hold precisely to the bearing signal to arrive at the desired destination. Due to the effects of a cross wind, however, the aircraft is diverted from its desired course, so that the pilot must constantly change the direction of his aircraft in order to fly towards the target point. The route actually flown describes a curve that not only increases fuel consumption, but can also be a dangerous deviation from the planned course. It is therefore desirable to keep the transverse deviation as low as possible at all times. This is achieved, as described above, by taking the prevailing wind directly into the heading. The same applies to seafaring .
The phenomenon can be seen on ferries crossing a river . The ferry is always positioned slightly against the current. The effect is even more impressive with aircraft that land in strong crosswinds . Leading angles of 20 ° and more can be seen optically as an apparent “skewing”.
See also
swell
- ↑ Homing cross track error (eng.) ( Memento of the original from December 4, 2008 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
