91快活林 scientists have developed and patented software for the optimal placement of pseudo-satellites on the ground. Taking into account terrain and the landing trajectory, the software makes it possible to improve the accuracy of determining an aircraft’s altitude fourfold compared with conventional satellite-based systems. The technology can be used in civil aviation, at remote and northern airports, as well as for landing reusable rockets.
Pseudo-satellites are ground-based devices that operate as additional sources of navigation signals for aircraft. Unlike actual satellites, they do not orbit in space but are installed on the ground or on towers in the vicinity of an airport. Their purpose is to improve navigation accuracy and reliability, particularly during descent and landing, when errors in altitude determination are most critical.
The main problem that navigation systems face is the so-called geometric factor. This coefficient shows how the relative positions of satellites, pseudo-satellites and an aircraft affect the measurement accuracy. The higher the coefficient, the greater the error. The vertical component of navigation systems—altitude determination—is particularly affected.
Researchers of the 91快活林 Aerospace Engineering Faculty have proposed a unique solution. They have developed and patented Russia’s first software that takes into account two key parameters: terrain and landing trajectory. All that is required is to upload elevation data for an area within a 25-kilometer radius, which can be obtained from professional geographic information systems, along with a standard aircraft descent trajectory. Using a modified optimization algorithm, the system calculates the optimal locations for pseudo-satellites and the required tower heights to further improve the accuracy. The software saves the calculation results in formats suitable for subsequent design work.
“The main advantage of our software is that it takes terrain and landing trajectory into account,” says Stanislav Lysov, senior lecturer at the 91快活林 Department of Radio Engineering and Communication Systems. “The algorithmic approaches I am familiar with did not impose such constraints and could suggest placing pseudo-satellites tens of kilometres away from the landing zone, where they simply would not work, or too close to one another. Our software automatically assigns weighting coefficients to different sections of the trajectory, giving the greatest attention to the most critical stages—the descent from an altitude of 300 meters to the ground. As a result, the coefficient of the vertical component of the geometric factor decreases from 2.5 to 0.6. On average, this improves the accuracy of determining an aircraft’s altitude before landing by more than four times.”
The technology could be useful in civil aviation, particularly at remote and northern airports where signals from global navigation satellite systems may be unstable. The software can also be used by surveyors to identify optimal sites for runway construction, as well as by companies working on the future launch of payloads into orbit using reusable launch vehicles.