Sparse sampling of signal innovations

Sparse sampling of continuous-time sparse signals is addressed. In particular, it is shown that sampling at the rate of innovation is possible, in some sense applying Occam's razor to the sampling of sparse signals. The noisy case is analyzed and solved, proposing methods reaching the optimal performance given by the Cramer-Rao bounds. Finally, a number of applications have been discussed where sparsity can be taken advantage of. The comprehensive coverage given in this article should lead to further research in sparse sampling, as well as new applications. One main application to use the theory presented in this article is ultra-wide band (UWB) communications

Corsica SLR Positioning Campaigns (2002 and 2005) for Satellite Altimeter Calibration Missions

International audienceThe French Transportable Laser Ranging System (FTLRS) was deployed in the calibration site of satellite radar altimeters in Corsica over the 2002 and 2005 campaigns. The paper describes the different steps of SLR data processing. The average arcs RMS obtained are about 1-2 cm for Lageos-1&-2, Starlette and Stella satellites; it is shown that the best results of satellite orbits determination and geocentric positioning are obtained with Eigen-Grace03s gravity model. The difference of FTLRS absolute 3D positioning, between 2002 and 2005, of about 7.7 mm (i.e., 2.6 mm/yr) is less than residual errors of ITRF2005 velocities (of about 4.3 mm/yr)

The Role of Laser Ranging for Calibrating Jason-1 : the Corsica Tracking Campaign

Marine Geodesy, v. 27, n. 1-2, p. 333-340, Special Issue on Jason-1 Calibration/Validation, 2004. http://dx.doi.org/10.1080/01490410490476272International audienc

Recent advances in the determination of a high spatial resolution geopotential model using chronometric geodesy

International audienceThis work aims to evaluate the contribution of optical atomic clocks in the determination of the geopotential at high spatial resolution. The quality of the geopotential reconstruction is evaluated by comparing solutions computed from synthetic gravimetric data, combined or not with synthetic clock data. Our synthetic tests are performed in a French area with a moderate relief, which leads to variations of the gravitational field over a range of spatial scales. We show that adding few clock data into a gravimetric network permits to reduce the reconstruction bias significantly and to improve the standard deviation by a factor 3. Optimization of a clock data network with a genetic algorithm is also investigated

Satellite Laser Ranging

International audienc

Geocenter motion measured by DORIS and SLR and geophysical expectations

Journal of Geodesy, v. 80, n. 8-11, p. 637-648, 2006. http://dx.doi.org/10.1007/s00190-006-0079-zInternational audienc

Analysis of C21 and S21 time series over long periods of time from SLR data

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Single-Frequency Receivers as Permanent Stations in GNSS Networks: Precision and Accuracy of Positioning in Mixed Networks

Continuous Operating Reference Stations (CORSs) are widely used for many purposes including precise positioning, mapping and monitoring. These architectures are composed of a control centre and a number of permanent stations consisting of geodetic antennas and dual frequency receivers. This infrastructure is costly due to the instruments used and has the additional disadvantage in that inter-station distances between CORSs, that are often too high if a single-frequency receiver acts as a rover. This study focuses on the usefulness of permanent single-frequency stations in order to increase density of existing CORSs for monitoring purposes. In this connection, some innovative GNSS networks composed of geodetic and mass-market L1 receivers have been developed and tested, analyzing the performance of rover positioning in terms of quality, accuracy and reliability in real time. Some tests have been carried out considering different types of receivers (geodetic and mass market) and antennas (patch and geodetic), in real-time mode. The results obtained show that with a "classical" network (where the mean inter-station distances between CORSs are about 40 km) an accuracy of about 5 cm can be achieved after fixing the phase ambiguity with a mass-market L1 receiver acting as rover. In addition, the Time-To-Fix period is very short, being less than 2 min. Despite the obvious fact that increased inter-station distance leads to reduced accuracy, the degree of precision obtainable remains useful for many applications, such as mobile mapping and traffic control. In short, the experiments under examination performed with low-cost GNSS receivers will be useful for many types of applications (landslide monitoring, traffic control), especially where the inter-station distances of permanent GNSS stations are around 40 km