User:Ludmilovna/Sandbox

WIDE AREA MULTILATERATION (WAM)

OVERVIEW
Wide Area Multilateration (WAM) is an independent, cooperative surveillance technology based on the same Time Difference of Arrival principals that are used on an airport surface. WAM uses widely distributed sensors over a large coverage volume to track aircraft in the air. It can interface to terminal or en-route automation systems.

SYSTEM PERFORMANCE
WAM provides flexible performance that is equal to or better than Secondary Surveillance Radar (SSR) in terms of accuracy, probability of detection, and update rate. Accuarcy varies as a function of the location of the targets vs. ground sensors.

WAM is highly adaptable to interrogation rates, output modes and output periods. Update rates and Probability of Detection can be tailored to various applications such as Precision Runway Monitoring (PRM), Terminal Maneuvering Area (TMA) and En-route surveillance. Interrogation rates can be further reduced by passively processing replies to SSR or Traffic Collision Avoidance System (TCAS) interrogations.

AVIONICS
WAM operates with Mode A/C, Mode S, and Mode S ES, no equipage mandate is necessary. For ADS-B equipped aircraft, WAM provides an ADS-B target report as well as a multilateration target report. WAM complements ADS-B by providing transitional surveillance for non ADS-B equipped targets, and can be used for ADS-B validation.

INTEGRATION INTO AUTOMATION SYSTEMS
WAM supports a variety of output modes and output formats. It can emulate an SSR by providing a periodic, azimuth ordered output.
WAM incorporates new output formats specifically designed for WAM and ADS-B:

ASTERIX CAT19 for WAM system status
ASTERIX CAT20 for WAM reports
ASTERIX CAT21 for ADS-B reports

IMPLEMENTATION CONSIDERATIONS – SITING AND INSTALLATION
The design of a WAM system is dependent upon proper site selections. Below are some issues to consider when selecting sites:

Accessibility (limited by terrain, weather,…)
Availability of power/backup power, communications
Site ownership: customer or local/state government owned sites may be preferred to commercial sites
Environmental impact
Available space
Interference with other site equipment
Site acquisition and preparation: leasing, permits, required construction, etc.
Installation season (extreme weather, high snows, high seas)
Accessibility during installation
Special training (survival training for oil platforms, tower climbing)

IMPLEMENTATION CONSIDERATIONS – COMMUNICATIONS
Availability of communications is an important factor in site selection. Bandwidth, latency and reliability all need to be considered. In many cases, a dedicated network is not available. The system needs to rely on third parry commercial communications such as local microwave networks, telecommunications provider, or satellite communications.