The quality analysis of GNSS satellite positioning data
Focused on the Beidou satellite system (BDS), dual satellite system (GPS/GLONASS) and three satellite system (BDS/GPS/GLONASS), the parameters influencing the quality of static and real-time dynamic positioning date of the GNSS systems, such as the multipath effect, ionospheric delay, data utilization rate and signal-to-noise ratio, number of satellites and accuracy factor PDOP value, have been comparatively analyzed in this paper. The results of tests have shown that compared to the single satellite system BDS the average multipath errors (mp1 and mp2) of multi satellite system fusion decreased by 18 and 8% respectively, due to the increase in the number of visible satellites in multi-satellite fusion, it is possible to compensate each other to a certain extent, thus weakening the influence of the multipath effect on the positioning results. When the cut-off angle is greater than 40°, the single system cannot meet the need of navigation and positioning, however having more visible satellites than the single system it is possible for multi satellite system fusion to maintain lower and more stable PDOP value for high precision positioning services.
A Comparative Analysis of the Response of GNSS Receivers under Vertical and Horizontal L1/E1 Chirp Jamming
Jamming is becoming a serious threat to various users of global navigation satellite systems (GNSS). Therefore, live monitoring tests are required to estimate the sensitivity range of GNSS receivers under jamming. This study analyses the response of some mass-market and professional-grade receivers to intentional interferences based on different 3D jammer positions. First, the vertical jamming was investigated, followed by a horizontal experiment where the receivers were placed at three locations while the jammer was moving within a triangular area. The aim was to determine a fingerprint of the influence of the L1/E1 chirp jammer on receivers used in the research. The results show that low-cost receivers are much more susceptible to interference, while the latest generation of GNSS geodetic receivers are much more resilient. It is encouraging that positioning in the presence of jamming could be achieved on a larger scale, especially by using professional receivers. An attempt to position the jammer will be left for trials when a more frequency stable device is applied.
Solution Hybrid Selection with Ultra-long Oligonucleotides for Massively Parallel Targeted Sequencing
Targeting genomic loci by massively parallel sequencing requires new methods to enrich templates to be sequenced. We developed a capture method that uses biotinylated RNA 'baits' to fish targets out of a 'pond' of DNA fragments. The RNA is transcribed from PCR-amplified oligodeoxynucleotides originally synthesized on a microarray, generating sufficient bait for multiple captures at concentrations high enough to drive the hybridization. We tested this method with 170-mer baits that target >15,000 coding exons (2.5 Mb) and four regions (1.7 Mb total) using Illumina sequencing as read-out. About 90% of uniquely aligning bases fell on or near bait sequence; up to 50% lay on exons proper. The uniformity was such that ∼60% of target bases in the exonic 'catch', and ∼80% in the regional catch, had at least half the mean coverage. One lane of Illumina sequence was sufficient to call high-confidence genotypes for 89% of the targeted exon space.