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 object's position. By using three or more sensors, a complete position analysis can be attained by determining the intersection point of the three or more hyperbolas formed by the TDOA from each sensor pair.
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

Szczecin, Poland May 13 to 17, 2013 Specialists’ meeting and a business meeting of SET (Sensors and Electronics Technology) Panel of the NATO Science and Technology Organisation (STO) took place in Baltic Barracks in Szczecin. The live demonstrations of Passive Coherent Locators (PCL) accompanied the meeting: ERA`s Silent Guard, PCL CASSIDIAN (Germany) and PaRaDe Politechnika Warszawska (Poland).
Pardubice, May 14th, 2013 ERA has recently been developing a Multistatic Primary Surveillance Radar (MSPSR) passive known also as a Passive Coherent Location system (PCL). The newest, mobile version of this technology for air to ground surveillance will be introduced to the general public for the 1st time at the IDET Exhibition 2013 in Brno.
Czech TV News, April 27th, 2013 Czech Public Television broadcasted the report on ERA`s PCL system demonstrator called Silent Guard in primetime of Saturday night. PCL demonstrator is another significant milestone in MSPSR project developing in the company.
Brno April 17th, 2013 In the mid April ERA Company traditionally became a partner of the conference PVO 2013 in Brno. The event was organized by the Department of Air Defence Systems in the club of Faculty of Military Technology of University of Defence in Brno.