The TLS is an precision approach system designed for use at airports where rough terrain or real estate constraints make Instrument Landing System (ILS) installation infeasible or cost-prohibitive. All IFR-equipped aircraft capable of flying an ILS can also fly the TLS without adding new avionics. TLS determines the aircraft’s position in space from signals emitted by the aircraft’s transponder, using time and angle measurements at ground-based sensors. Localizer and glide slope corrections are computed to guide the aircraft to the desired course and appear in the cockpit just as ILS corrections do. TLS is inherently easier to site than ILS and therefore can be less costly to install, providing signals-in-space for horizontal and vertical guidance without extensive ground conditioning. Traditional Instrument Landing System glideslope equipment can be difficult to site at airports on or near rough terrain, and in some cases cannot be used without extensive earth removal to reduce errors induced by multipath, or ground-based reflections. Additionally, ILS localizer performance can be diminished by multipath from large buildings located on the airport property, and restrictions to aircraft and vehicular movements can significantly reduce airport throughput when critical area protective measures are in effect. At some airports where the runway is shorter and ends at obstacles like water, an ILS localizer installation may not be possible that achieves the ICAO required tailored width of 700 feet at threshold and a maximum 6.0 degree localizer course width. For these short runways the virtual flight path provided by TLS can over come this problem and provide localizer guidance centered on the runway without the need for an offset localizer. The TLS was designed to alleviate these problems by providing a virtual approach path, compensating for multipath and minimizing the equipment footprint, providing all-weather accessibility to airports that cannot site traditional ILS equipment, and with minimal real estate and critical area requirements. Because the TLS uses legacy airborne equipment and requires no new avionics, and because the approach procedure is nearly identical from the pilot’s perspective, operator costs to fly the TLS are minimal. The Federal Aviation Administration has granted the TLS regulatory approval. The TLS complies with the RTCA DO-178B reliability standard for airborne software and the SAE ARP 4754 certification model for highly-integrated or complex aircraft systems.