Multilateration, or hyperbolic positioning, is the process of locating an object based on the Time Difference of Arrival (TDOA) of a signal emitted from that object to three or more sensors. When a signal is transmitted from an object, it will be received by two spacially separate sensors at different times. The time difference is then used to calculate the objects position. By using three or more sensors, a complete position analysis can be attained by determining the intersection point of the three or more hyperbola formed by the TDOA from each sensor. 

For ATM applications, multilateration provides the same level of fleet coverage as traditional SSR (ie. all aircraft or vehicles equipped with an operational Mode A, Mode C or Mode S transponder) while also decoding all ADS-B position reports. Multilateration will generally provide higher accuracy, greater update rate, better coverage and improved reliability when compared to traditional SSR, and will do so at a much lower initial cost and with 

“ERA’s multilateration systems have a long track record of performance and reliability in both surface and en-route applications. The bottom line is that they just work and they work better and more economically than SSR.”

- Mr. Ivan Uhlir, Czeh ANS

“We evaluated surveillance solutions and concluded multilateration provided the best surface coverage and the flexibility to accommodate our future growth. After a competitive evaluation, ERA was chosen by Siemens for its leading technology and proven delivery capabilities supported by an extensive list of worldwide references.”

- Peter Marais, Executive Manager ATM/CNS Planning for ATNS