Applications of global navigation satellite systems in upper and lower atmosphere research over the Philippines


  • Ernest P. Macalalad Department of Physics, Mapúa University


Global navigation satellite systems (GNSS) were originally used for the navigation of vehicles and other related activities. Given the time of flight of the radio waves obtained by the receiver from the satellites, the receiver calculates its geographic position. However, these radio waves encounter several sources of errors, such as receiver and satellite biases, orbital errors, relativistic effects, and atmospheric effects. Only after removing these errors can one determine its position accurately and precisely. In recent years, GNSS has been used to study lower and upper atmospheres. Here, the errors brought about by lower and upper atmospheric effects are used to estimate specific atmospheric parameters, such as precipitable water vapor for the lower atmosphere and total electron content in the upper atmosphere. Precipitable water vapor is a quantitative measure of the moisture content in the atmosphere. It is a measure of how much moisture can be converted into precipitation, which has a great effect on hydro-meteorological processes.
On the other hand, the total electron content measures the ionization in the ionosphere (the ionized part of the upper atmosphere). The ionization in the region brought about by solar radiation affects radio-wave propagation. At lower frequencies, the ionosphere acts like a mirror where signals from the ground can traverse farther distances through reflection off this layer. At higher frequencies, radio waves pass through. Any transient changes in the state of the ionosphere could affect technological applications that use radio wave propagation, such as navigation and communication. In this work, observations of these parameters are done over the Philippine context—this research is done to understand better how these parameters vary in time and space.

About the Speaker

Ernest P. Macalalad, Department of Physics, Mapúa University

Ernest P. Macalalad graduated with a degree of Doctor of Philosophy in Space Science at the Graduate Institute of Space Science of the National Central University in Taiwan, where he specialized in global navigation satellite systems and ionospheric modeling. He also earned his degrees of Bachelor of Science in Physics and Master of Science in Physics from De La Salle University in Manila.
Dr. Macalalad is currently a faculty member of the Department of Physics at the Mapúa University in Manila. He has experience teaching university physics and some advanced courses physics such as classical mechanics, electromagnetic theory, and computational physics. Aside from his teaching duties, he is currently the faculty-in-charge of the BS Physics program. Prior to his work at Mapúa, he was a postdoctoral fellow at the Center for Space and Remote Sensing Research in National Central University from 2014 to 2015.
He also heads the Space Environment and Atmospheric Research group of his department where they use various satellite and ground-based systems for space and atmospheric observations. Using global navigation satellite systems (GNSS), they study the effects of solar and geomagnetic activities in the ionosphere for communications and navigation applications, and measure and monitor atmospheric water vapor.



Article ID



Invited Presentations



How to Cite

EP Macalalad, Applications of global navigation satellite systems in upper and lower atmosphere research over the Philippines, Proceedings of the Samahang Pisika ng Pilipinas 40, SPP-2022-INV-3F-04 (2022). URL: