Ostrava, the country’s third-busiest airport, is located among mountainous
terrain in the northeast sector of the Prague flight information region (FIR). In
2000, members of the Czech Air Navigation Services (ANS) decided to improve
their air surveillance systems. The purpose of the system was to cover the
Terminal Control Area Ostrava with respect to low altitudes and final approach
areas and place a reliable cooperative sensor in this sector of the Prague FIR.
Until this point, only expensive SSRs were certified for air traffic separation. In
the eyes of the Czech ANS, SSR was not only a costly alternative but was also
an ineffective one in the face of the Ostrava terrain. The nearest Secondary
Surveillance Radar (SSR) could not provide coverage below 1000 m, as the
surveillance range of the SSR could not dip below the crests of the mountain
range. The Czech ANS surveillance experts began researching emerging
technologies as alternatives to traditional radar solutions.
The ANS of the Czech Republic contracted the ERA Company’s MSS
multilateration system as a substitute for the Secondary Surveillance Radar
(SSR) in 2001. The decision was based on a lengthy performance and cost/benefit
analysis, which clearly determined that ERA’s wide area multilateration solution
could outperform the traditional SSR at a fraction of the cost. At present the
system in Ostrava is not only a substitute for the radar, but has also introduced
new features which are appreciated by the controllers. First and foremost, it is
absolutely reliable. The MTBF (Mean Time Between Failure) of all the modules
included in the Ostrava airport’s system is approximately 600,000 hours.
The ERA system was fully installed and approved by SAT at the end of 2002
and type certified in 2003 against ICAO ANNEX 10 for interrogation and against
Eurocontrol radar standards for surveillance performance after one year of
trouble-free operations. The system performed so well during that year that
it was certified and can even be used for 3 Nautical Mile (NM) separations. It is
believed to be the only operational multilateration system in the world with
such certification to date.
Description of the system
The original WAM system in Ostrava consists of five receiving stations based
on central time architecture and two interrogators and provides ASTERIX data
to the ATC systems both in Ostrava and in Prague along with the Remote
Control and Monitoring Systems (RCMS) established in both centres. The system
(currently consisting of seven GS) contributes to the overall ANS radar network
and remains the only equipment to control separation between incoming and
outgoing aircraft at Ostrava Mosnov airport. The system tracks aircraft down to
the gate with an accuracy corresponding to the airport A-SMGCS sensor.
The Mosnov airport system based on central time architecture was extended in
2009 by six ground stations based on distributing architecture to provide surface
surveillance of the airport and expand WAM coverage of the surrounding area.
The picture shows
the actual coverage
and accuracy after
the last extension
at the flight level
100 (that means sea
level 3050 metres).
extends 80 NM from
the Ostrava airport
all the way down to
the airport surface.
systems have a
long track record of
reliability in both
surface and en-route
applications. The air
(ANS) of the Czech
Republic have made
extensive use of
since 1999 and we are
the extension of
for WAM Ostrava.
ERA's systems truly
work and they work
than SSR. They
also meet current
as they contain 70 %
software and only 30 %
hardware. This means
less energy and easier