It has been some time since the GPS and BeiDou signal anomaly incident in Nanjing. While the cause of the incident remains debated, an interesting question has been frequently discussed in the 'Malagis' GIS group recently: If one day, both our GPS and BeiDou signals are abnormal, and we don't have access to military-grade bands, how can we determine our location? The author has previously written a bit on this topic. Drawing from the group members' discussions and collected materials, here is a summary. Corrections are welcome if any inaccuracies are found.
Before delving into this topic, let's introduce a new concept: All-source Positioning. In this era of the Internet of Everything, the heavily relied-upon GPS is not omnipotent. Satellite signals cannot penetrate thick reinforced concrete or travel underwater. All-source positioning involves integrating various other sensors to provide alternative solutions when GPS fails. So, what are the current common solutions? Let's explore them.