GPS satellite signals experiment a delay when they go through the atmosphere. One of the applications of GPS data processing is the extraction of atmospheric water vapour content from the tropospheric delay in the GPS measurements. Information about water vapour content in the air is useful as input for weather forecast models.

In order to demonstrate the capabilities of magicGNSS for weather prediction applications, we have set up a testbed to process 5 GPS stations in Madrid, Spain. The stations are called: gap1, igne, mad2, madr, and vill. The maximum distance between any pair of stations is around 50 km. The mad2 and madr stations share the same location, therefore their zenith tropospheric delays should be identical.

The near-real time station data is processed by the Precise Point Positioning (PPP) algorithm. The station data is processed automatically every hour using the new Scheduler in magicGNSS. The results are shown on the following live plots, updated 35 minutes after the hour. Time is UTC.

gap1 Zenith Tropo Delay

igne Zenith Tropo Delay

mad2 Zenith Tropo Delay

madr Zenith Tropo Delay

vill Zenith Tropo Delay

The Russian navigation system GLONASS seems to be in very good shape again. Since February 4, eighteen (18) satellites are continuously available for dual-frequency Precise Point Positioning (PPP). Now it is possible for example to monitor the behaviour of a very stable atomic clock connected to a GNSS receiver, using GLONASS measurements exclusively, without GPS.

We have processed in PPP data from the svtl station near Saint Petersburg in Russia. This station is connected to a hydrogen maser. Station measurements were taken during February 5. The GLONASS orbit and clock products needed for PPP have been generated internally and are available in magicGNSS. The following figure shows the resulting PPP pseudorange (code) and phase residuals, for the 18 GLONASS satellites.

Pseudorange (code) and phase residuals from PPP

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We have just released magicGNSS version 2.2 which incorporates a new version of the Precise Point Positioning algorithm (PPP). The new PPP is able to process the Russian satellite constellation GLONASS.

GLONASS satellite orbits and clocks needed as input by PPP have been calculated offline using the ODTS module of magicGNSS. GLONASS orbits and clocks are available starting January 1, 2010, with a latency of around 1 hour. The new PPP has three processing modes: GPS-only, GLONASS-only, and GPS+GLONASS. It is also possible to do GLONASS PPP by email.

magicGNSS/PPP with GLONASS was presented and demonstrated at the ION GNSS 2009 conference in Savannah, Georgia, USA. The title of our paper was Orbits and Clocks for GLONASS Precise-Point-Positioning.

Three new GLONASS satellites were launched last December 14. Their orbital slots or PRN numbers are: 01, 04, 05. Number 05 (R05) has been declared operational on January 10 (see the GLONASS constellation status).

Since version 2.0 magicGNSS is able to calculate GLONASS satellite orbits and clocks using the Orbit Determination & Time Synchronization algorithm (ODTS). 15 Russian satellites can currently be processed in ODTS, from a total of 16 operational ones (R19 cannot be processed because it only transmits in L1). The following plots show our GLONASS orbit and clock estimation accuracy (actually precision or internal consistency), from comparing overlapping ODTS arcs.

GLONASS orbit accuracy

GLONASS clock accuracy

The PTTI conference finished today. Here is our presentation. This is a photo of our booth at the Exhibition: