Doppler GDOP Lower Bound for Different LEO Constellations of Opportunity Positioning

To address the weak anti-interference capability of the conventional global satellite navigation system (GNSS), a navigation system based on the opportunity signal of LEO constellation is studied to complement and enhance it. Since LEO satellite opportunity signal generally adopts the Doppler positioning method different from GNSS, the Doppler geometric dilution of precision factor (DGDOP) lower bound expression and variation law for LEO satellite positioning are studied in depth in this paper, to assess the limitation and potential of positioning in different LEO constellations. The paper analyzes the variation law of visible satellites and DGDOP with latitude for different LEO constellations using the actual LEO satellite orbit data output from the system tool kit (STK) platform, and verifies the validity of the analytical expression for the lower bound of DGDOP.