The Rate Of TEC Index (ROTI) is a commonly used measure of ionospheric activity. ROTI values have been computed every 5 min for the year 2012, for 10 receivers at latitudes from 59°to 79°North. We present the results in geomagnetic coordinates, showing that elevated ROTI values occur mainly in the cusp and nightside auroral oval regions. Elevated ROTI values are more common in the cusp, but in the nightside auroral oval they are stronger. To investigate the relation to positioning errors, receiver coordinates were computed using the GIPSY software, for the same receivers and time resolution. We found that there is a strong positive correlation between Precise Point Positioning (PPP) error and ROTI for receivers that are affected by space weather. The 3D position error increases exponentially with increasing ROTI. A statistical analysis presents also the risk of having several satellites observing enhanced ROTI values simultaneously, showing that this risk is greater at high latitudes.
<p><em>Where</em> is a software package developed by the Norwegian Mapping Authority (NMA). The software will provide a useful contribution to the International Terrestrial Reference Frame, by analysis of data from Very-long-baseline Interferometry (VLBI) and Satellite Laser Ranging (SLR).</p><div><em>Where</em> is written in Python, and is taking advantage of well-tested code like the SOFA and IERS libraries. The architecture is easily maintainable and extendable. Python makes it easy to write, and utilizes external libraries written in faster languages.</div><div>&#160;</div><div>Both the NMA and the Instituto Geografico Nacional, Spain, are in a test phase of deliveries of VLBI analysis results to the IVS with the <em>Where</em> software. After some improvements of the software, we will also deliver analysis results to the ILRS. Our goal is to receive full status as operational analysis center for both VLBI and SLR, and to contribute to ITRF2020.</div><div>&#160;</div><div>Sharing and cooperating with other institutions is made possible by making <em>Where</em> an open source project on GitHub.</div>
The Galileo High Accuracy Service (HAS) is currently in its testing phase, in which actual corrections are transmitted along with standard dummy messages. The dissemination of Precise Point Positioning (PPP) corrections is performed using an innovative scheme based on a Reed–Solomon code, which allows the reconstruction of the original navigation message from a subset of received pages. This approach introduces robustness to the reception process and aims at reducing the Time-to-Retrieve Data (TTRD); that is, the time to retrieve the HAS message. This study investigated the HAS demodulation performance considering Galileo signals collected at high latitudes. In particular, a Galileo E6-capable receiver was mounted on a vessel sailing from Bergen to Kirkenes, Norway, and reaching up to 71 degrees North. The trajectory of the vessel was at the border of the Galileo HAS service area and high-latitudes impact reception conditions, potentially leading to poor satellite geometries. Three months of data from January to March 2021 were analyzed, considering several metrics including Bit Error Rate (BER), Page Error Rate (PER), and TTRD. The analysis shows that the Reed–Solomon scheme adopted for data dissemination is also effective at high-latitudes, with daily PER below one percent and mean TTRD in the order of eight seconds when three satellites are broadcasting valid HAS corrections. Lower values of the TTRD are achieved with an increased number of satellites. These values are significantly lower than the update rate of the corrections broadcast by the Galileo HAS.
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