Estimating the position of targets in an area of interest is a well-known problem. Passive or active direction finding (DF) sensors, acquire bearings to targets. These bearings are then processed, using triangulation and other methods, in order to provide position estimates.
Correlation Systems has improved conventional triangulation methods, developing software positioning solutions for various types of sensors, such as: communication intelligence (COMINT) passive sensors, computer vision (video) sensors, and more.
When available, global navigation satellite systems (GNSS), such as GPS (and the future Galileo), provide the position of objects, with an accuracy of up to a few meters (usually with the help of augmentation services). Collecting GNSS positioning reports is equivalent to the previously discussed technology, and both enable target tracking, behavior analysis, and geographic data mining.
When dealing with mobile targets, the estimation of the object's position in a specific point in time is not enough. It is necessary track the target over space and time. Tracking is based on statistical models, such as the Kalman Filter, with particular dynamics models that match different targets' spatial behaviour.
In cases where positioning is not trivial, tracking is integrated within the positioning system, increasing the statistical probability of the position estimates.
Multi Hypotheses Grid Based Tracking
The use of multiple sensors for Positioning and tracking is not always possible. Operational constrains may impose situations in which the accurate positioning of a target and the estimation of its movement must be achieved through the use of a single mobile passive sensor.
Correlation Systems provides a tracking technique which successfully tackles this problem. The technique is based on the use of multi hypotheses, generated as a result of the integration of the target's bearings and the sensor's location, speed and heading.
The tracking results are given in the form of a moving target's trajectory estimate, as well as an estimate of the number of targets present in the arena.
A single DF sensor, measuring both the direction of arrival (DOA) and the elevation of arrival (EOA) of high frequency (HF) radio waves, can estimate the position of HF transmitters. This technique, which involves only a single sensor and is not based on triangulation, is called single sensor location or SSL.
SSL calculation is based on estimating the HF radio waves propagation, effected, mainly, by their reflection from the ionosphere, which is influenced by a number of factors, including the time of day and the occurrence of solar flares and sunspots.
Sunspot
prediction until 2025