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this paper presents a navigation system design for airborne drone-based applications. The proposed operation principle includes visual/inertial tightly coupled integration based on an extended SLAM approach. In addition to the opportunity-based features that are used by similar to the standard SLAM solutions, the proposed approach also utilizes internal landmarks that are created by the algorithm itself. This method allows reducing the drift that is typical in SLAM -based solutions in addition to reducing the algorithm complexity. Adding a small number of global landmarks helps eliminate the remaining drift. The design goal is to use global coordinates during the entire operational cycle. For a 200m altitude flight, with 2 global landmarks, partially available, the system converges fast to high accuracy with respect to the global reference, without any SLAM drift. While for lower altitudes (100 m), only near-tactical grade IMU provides a very low SLAM drift solution. The significance of the work lies in showing the complete design of a global-coordinate drone SLAM system with the fusion of inertial sensors, taking into account tradeoffs on trajectory profile, sensor grades and global landmarks availability.

This paper describes a new method for error model construction. Instead of the standard local slope analysis of the Allan variance, two major modifications are proposed: (1) the Direct Bound principle, i.e. finding an entire error model that generates analyzing tool values that tightly bound the analyzing tool values generated by the real data; (2) instead of using Allan variance as a unique analyzing tool, a variety of analyzing tools termed Direct Predictor (DP) types 0, 1, 2, and 3 are introduced. In the paper, a uniform structure of DPs is developed and their parameterization is extended. For a nominal model that consists of a Markov process with additive white noise, the analytical functions for DPs are presented (for infinite data length). The errors due to the final data length are analyzed. Using these results, a reliable optimization problem is presented to implement the Direct Bound approach. The flexibility of working with hard and soft bounds is introduced. The presented simulation results show that the proposed method is indeed efficient and provides satisfactory results for model parameter estimations. The paper concludes with a description of an entire engineering process to cover test design and its analysis.

In the late seventies and early eighties, Rafael devolved a very advanced (at the time) transfer alignment algorithm. This required the development of an entire infrastructure for navigation work: strapdown navigation equations, navigation error model, Kalman filter implementation, system level error model, inertial measurement unit, real-time, floating-point computer, test design, implementation and analysis. This paper tells the story of this enterprise, from the preliminary studies to successful operational deployment, by pointing out the different phases and lessons learned.