CARROLL MCCORMICK / MONTREAL
MDS will better handle multi-path and false targets from buildings, signs and snow banks
Austria's Vienna and the Netherlands' Schiphol international airports have contracted Sensis to install multilateration/multistatic dependent surveillance (MDS) systems to enhance their surface and air coverage.
The Schiphol project is in the design review stage, while site surveys have been completed at Vienna and its MDS system is under construction. The Vienna and Schiphol systems are scheduled to begin operating in January and second quarter 2003, respectively. MDS will augment Vienna's Ku-band surface movement radar (SMR) and Schiphol's Ku-band, and new Terma X-band SMRs.
"With a distributed system like MDS, you can concentrate on [positioning SMR in] your movement areas and use MDS to fill in the gaps," says Sensis's vice-president sales and marketing Ken Tollstam. Unlike primary "skinpaint" radar, MDS deals better with multi-path and false targets from buildings, signs or snow banks.
MDS systems typically have six to 12 sensors to provide blanket coverage and fill blind spots hidden from SMR. The sensors receive Mode A/C and Mode-S transponder transmissions about once per second and calculate aircraft positions, with an error on the surface of about 6.25m (10ft), using a form of triangulation. Sensis systems support more than 450 target reports per second and much higher update rates in conflict situations.
MDS also receives automatic dependent surveillance-broadcast transmissions - an MDS reference transmitter synchronising source is independent of the global-positioning system.
The data, showing altitude, aircraft identity, latitude and longitude, velocity and heading, is fused with SMR data and presented on tower controllers' displays. MDS can also support universal access transceiver digital data and will be able to receive VHF digital link Mode 4.
MDS is also part of the US Federal Aviation Administration's APDE-X system.
Source: Flight International
