Achieving a successful aircraft landing demands reliable and safe approach guidance, particularly under low visibility conditions. Although various aircraft landing guidance systems coexist in aviation, this thesis concentrates on a comparative analysis of the Instrument Landing System (ILS) and the Ground-Based Augmentation System Landing System (GLS) from multiple perspectives. The fundamental principles of each system are explained in detail to provide distinction between their operational and technical characteristics as well as their working mechanisms. Core differences and similarities between ILS and GLS are subsequently compared in terms of accuracy, reliability, safety, and economic considerations. Furthermore, a case study is presented to illustrate the current application of both systems, followed by future trends in landing guidance technologies. Through this comparative analysis, the thesis provides a comprehensive understanding of ILS and GLS, including their distinctions and potential contributions to aviation.