Welcome Galileo-FOC FM4!

May 25th, 2015 by Guillermo Tobías

After its launch back on March 27 , Galileo-FOC FM4 (GSAT0204) started transmitting on May 21th at about 11:32 UTC, being tracked at that time by the International GNSS Service Multi-GNSS Experiment tracking station in Windhoek, Namibia with PRN E22 (http://gpsworld.com/newest-galileo-satellites-now-transmitting/).

As for the previous FOC satellites, a magicODTS scenario has been configured using MGEX station data for May 23rd and May 24th, and setting WTZR as reference station.

The obtained results are below. Satellite code-phase and carrier-phase residuals:

The following plot shows the Galileo-FOC FM4 apparent clock estimation w.r.t WTZR station:

Following you can find the GPS and Galileo clock stability:

From the above results it seems as the IOT for Galileo-FOC FM4 is running quite smoothly,  let’s hope Galileo-FOC FM3 starts transmitting soon too!

Congratulations to ESA and the Galileo project!!

Second FOC Galileo satellite already processed by magicGNSS!

March 20th, 2015 by Guillermo Tobías

As mentioned in a recent article by GPS World (http://gpsworld.com/galileo-6-signals-acquired/), “On March 17, some stations participating in the International GNSS Service Multi-GNSS Experiment acquired E1 and E5a signals from Galileo 6 (FOC-FM2, GSAT0202). The satellite is using pseudorandom noise code E14.”

Analysing the RINEX data collected by the MGEX network, it seems that at least one clock correction (between 2015/03/19 00:40:00 and 02:00:00 UTC ) has been applied to the on-board atomic clock.

A magicODTS scenario has been configured using MGEX stations and removing all data for E14 prior to that apparent clock correction. The obtained results are below.

Satellite code-phase and carrier-phase residuals:

E14 apparent clock estimation w.r.t WTZZ station:

Apparent satellite clock stability:

Not enough data has yet been collected (roughly 24 hours of data) in order to perform a consisteny analysis, but the initial estimation shows an apparent clock behaviour for FOC-2 satellite which is in line with the expected performances from the Galileo satellites.

These are great news for the Galileo project!!

 

Multi-GNSS Precise Point Positioning

January 8th, 2015 by

We have just released magicGNSS version 5.5 which incorporates a new version of the Precise Point Positioning algorithm (PPP). The new PPP is able to process GPS, GLONASS and GALILEO.

Multi-GNSS precise satellite orbits and clocks needed as input by PPP are computed beforehand using magicGNSS‘ ODTS module. Multi-GNSS orbits and clocks are available starting January 1, 2014, with a latency of around 1 day. The new PPP has the following processing modes: GPS-only, GLONASS-only, GPS+GLONASS, GALILEO-only, GPS+GALILEO, and GPS+GALILEO+GLONASS. It is also possible to use the PPP service by email.

magicGNSS/PPP with MULTI-GNSS support  was presented and demonstrated at the ION GNSS 2014 conference in Tampa, Florida, USA. The title of our paper was “magicGNSS‘ Real-Time POD and PPP MULTI-GNSS Service”.

About station icons

January 8th, 2015 by

Just a quick explanation about the meaning of station icons in magicGNSS:

GPS+GLONASS core station

GPS core station

deselectedDeselected station

reference_clockReference clock (in ODTS)

GPS+GLONASS user station with precise coordinates

GPS+GLONASS user station (or rover) with approximate coordinates

GPS user station with precise coordinates

GPS user station (or rover) with approximate coordinates

GPS+GLONASS public station with precise coordinates

GPS+GLONASS public station with approximate coordinates

GPS public station with precise coordinates

GPS public station with approximate coordinates

Multi-GNSS core station

Multi-GNSS user station with precise coordinates

Multi-GNSS user station with approximate coordinates

First Galileo-only PPP with IOV + FOC-1 satellite

December 11th, 2014 by Guillermo Tobías

It has been over one week now since Galileo FM5 started transmitting. The early results obtained with magicGNSS when processing the data collected by IGS’ MGEX network (http://igs.org/mgex/) during November 29th and 30th were quite preliminar, as they showed what seemed to be corrections being applied to the on-board atomic clock.

The results obtained when processing more recent data (from December 5th to December 9th, as it can be seen in the figure below), show a much more stable clock behaviour for FM5 satellite, which may lead to conclude that the apparent clock corrections have been successfully performed.

Based on this assumption, 2 consecutive 4-day long ODTS arcs have been executed with a 24 hour delay between them, and the overlap for the Galileo satellites, both for the orbit and the clock estimates, has been computed. The results presented below show that the orbit and clock consistency for all the Galileo satellites (both the IOV and the FM5), are in the same order of magnitude.

Galileo clocks consistency:

Galileo orbit consistency:

Despite the fact that the orbit and clock determination accuracy for FM5 can still be improved given the comparison with respect to the results obtained for the IOV satellites, the estimates can be considered accurate enough for thinking about using them for High Accuracy Positioning purposes.

In this regard, a Galileo-only PPP (3 IOV satellites transmitting in more that one frequency + FM5) has been run for LLAG station using as reference products the aforementioned estimates.

This GPS+Galileo MGEX station is located in the Canary Islands, and during December 6th the 3 usable IOV satellites ( PRNs E11, E12 and E19) and FM5 (PRN E18) satellite were visible over that station for around 2 hours, which allowed the computation of a Galileo-only PPP solution for LLAG station.

The estimated station coordinates were compared with the reference ones, which had been previously computed by means of a 24-hour long batch PPP using IGS reference products. The comparison shows that the Galileo-only PPP solution error is at the centimetric level. However, these results are quite optimistic due to the fact that the PPP estimated a single position based on a 2-hour data batch. In this regard we intend to perform a sequential Galileo-only PPP in order to obtain more realistic results about the positioning performances that could be achieved in a Real-Time environment.

Although this analysis can still be understood as a proof-of-concept, the presented results show the feasibility for using E18 satellite for High Accuracy, which can be considered as great news for the GNSS community!

Let’s hope that FM6 satellite follows the same path as FM5 so that it brings benefit for the GNSS community and in particular for High Accuracy purposes.