ARIADNE: Accurate visual marker based rapid initialization of PPP

Precise Point Positioning (PPP) has some advantages against Real-Time Kinematic (RTK) positioning in that it does not need ground base stations and does not require a rover to equip communication channel with the base stations. Therefore, it is expected that PPP is applied for a variety of fields such as precise agriculture, intelligent transportation, construction, and mining etc. One of the major drawbacks of PPP is that it takes several tens of minutes for initial convergence to reach adequate accuracy level, and the key issue at the spread of PPP is how to shorten the convergence time. In this paper, we propose a method for reducing this initial convergence time of PPP drastically by making use of an accurate fiducial marker. A camera is equipped on board of a rover in addition to GNSS antenna and receiver, and its relative position with respect to the antenna is measured in advance. When the system is launched, images of the fiducial marker, which is fixed at the location where initialization of the positioning system is needed, and whose position in earth fixed coordinate has been measured accurately, are acquired by the camera. Because relative position and orientation of the camera with respect to the marker can be measured very accurately with a specialized fiducial marker, the position of the camera and antenna in the earth fixed coordinate is obtained. And this position information makes it possible for PPP to converge within a minute by providing that information to the navigation filter as the initial value. In addition, we also present some techniques to: (1)estimate marker's position and orientation using GNSS positioning, (2)verify the result of initialization, to make the above initialization method more practical and reliable. Experimental results show that above method and techniques work very well with a realistic set up of PPP and marker performance, and successfully reduce the initial convergence time from tens of minutes to less than a minute.