MLAT or multi-lateration is an advanced positioning system typically utilized in civil and military airports. The main purpose of this system is to accurately localize airplanes and/or assets on the surface of the airport (MSS-A) or within TMA and En-route (MSS-W/WAM), while maintaining a high level of precision, regardless of weather or visibility conditions.
MLAT for airport-surface positioning reduces the risk of collisions and accidents. Airports operate in a very busy environment, with increased likelihood of confusion when visibility is limited due to weather conditions. The further an aircraft flies from the airport, the closer the sensors become in relation to the ranging distance. Hence, not all of the airport-surface sensors will add a value to the MSS-W system as the case of MSS-A.
Airport structures, such as buildings, are less important in this case, given that the nominated sensors and interrogators have a good clearance and sky visibility. This is the reason why 3D data is not required for WAM simulations. While the WAM deployment approach is apparently similar to that at the airport surface, the calculations differ.
MSS-A sensors must operate in LOS conditions, which can be translated to 60% Fresnel Zone (FZ). The propagation model must be configured to predict LOS coverage only. Upon completion of coverage calculations, heat-maps are generated.
It should be note that MSS-A networks such as interrogator(s) and sensor devices are static. However, the transponder installed on the asset is mobile. As a result, every pixel within the airport is a potential transmitter that needs to be able to transmit the signal to a minimum of 4 sensors.
ICS telecom EV can assess the performance of every location by checking the profile of every pixel back to each sensor. An easy way to evaluate the requirement is to predict a coverage overlap. The locations with more than three overlaps are termed as good locations. Connection functions help the user manually inspect an aircraft location and display visually the sensors that can receive the signal.
To predict MSS-A accurately, the user needs to left click the ULC and LRC of the area to be evaluated. Select “Multilateration” and then “TODA H”. The ITU aeronautical propagation model P.528 is recommended for MSS-W predictions. It is also recommended to incorporate the diffraction effect in line with ITU-R P.526 Annex 1, section 4.4.2 to assist in predicting shadowing due to the surrounding terrain.
For MLAT accuracy predictions, use TDOA+TSOA method for TMA. The output from the TMA simulation is the poor performance achieved in some part of the airport. ICS telecom EV has two techniques to find identify optimum site locations for coverage: Find highest point and Site search.
ATDI: Accurately improving MLAT performance