International audienceThis study presents a review of the state-of-the-art and a novel classification of current vision-based localisation techniques in unknown environments. Indeed, because of progresses made in computer vision, it is now possible to consider vision-based systems as promising navigation means that can complement traditional navigation sensors like global navigation satellite systems (GNSSs) and inertial navigation systems. This study aims to review techniques employing a camera as a localisation sensor, provide a classification of techniques and introduce schemes that exploit the use of video information within a multi-sensor system. In fact, a general model is needed to better compare existing techniques in order to decide which approach is appropriate and which are the innovation axes. In addition, existing classifications only consider techniques based on vision as a standalone tool and do not consider video as a sensor among others. The focus is addressed to scenarios where no a priori knowledge of the environment is provided. In fact, these scenarios are the most challenging since the system has to cope with objects as they appear in the scene without any prior information about their expected position
International audienceIonospheric scintillations are created by diffraction when the transmitted propagating waves encounter a medium made of irregular structures with variable refraction indexes. The recombination of the waves after propagation can be constructive or destructive and the resulting signal at output of the receiver antenna may present rapid variations of phase and amplitude. The carrier phase is traditionally tracked in the GNSS receivers using PLL, potentially aided by FLL. Phase Loops are known to be less robust than code tracking loops, and the GNSS receivers may thus suffer from phase tracking loss. This strongly impacts the positioning service availability, as well as the capability to demodulate the navigation message data, in situations where ionospheric scintillations affect the received signal. One thus has to implement innovative techniques and receiver architectures to provide robust carrier phase tracking. The aim of this paper is therefore to present the development of a GPS L1 phase tracking technique based on a Kalman Filter PLL [10] improving the tracking robustness in presence of ionospheric scintillations, and to present results of its performance using simulations. This paper is related to the paper presented at ION GNSS 2012 by C. Macabiau [1]
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.