Digital phase-locked loop (DPLL) and Kalman filter both have been widely used as the clock tracking and

clock correction schemes for the similar structure and properties.

The satellite

clock correction is calculated based on parameters transmitted in the satellite navigation message.

The accuracies of orbit and

clock correction products and error models to be used in determination have significant importance on the point positioning accuracies to be achieved in PPP method.

To achieve better curve fitting, here, we design the "satellite-clock-aided curve fitting" strategy which applies the satellite

clock correction. First, we extract the high-precision satellite clock information from the International GNSS Service (IGS) clock file.

Car clockers are so blatant that they openly advertise their "car

clock correction" services on the internet.

Caption: Figure 4: RTS

clock correction and prediction result (PRN 08, January 18, 2016).

The REFSV field contains the satellite

clock correction. The software obtains this information in one of two different ways, depending upon the OEM receiver board in use.

We introduced Kalman filter (Strang and Borre, 1997) in the final phase of data processing for dynamic recursive estimation of set of unknown parameters--site coordinates, correction to initial ambiguities and actual receiver

clock correction.

Tender issueThis EXPRO+ procurement is part of the NAVISP Programme under Elelment 1 Work Plan 2017.The object of the activity is to design develop and validate/verified a GNSS space receiver capable to perform on board precise orbit determination (P2OD) in real time using precise GNSS orbit and

clock corrections provided either by Geostationary satellites (thus allowing on board autonomy w.r.t to ground stations).

Clock corrections are given as offsets to the Broadcast Ephemeris satellite

clock corrections (http://igs.org/rts/products).

Where [[DELTA].sub.C] contains various

clock corrections, r is a vector from the barycentre to the telescope, [??] is a unit vector pointing from the barycentre to the pulsar, c is the speed of light, d is the distance to the pulsar, D is the interstellar dispersion constant,/is the radio frequency, [A.sub.E[?]] is the Einstein delay comprised of the gravitational red shift and time dilation, [[DELTA].sub.S[?]] is the Shapiro delay characterising the curvature of space time near the Sun and [[DELTA].sub.A[?]] is the aberration delay as a result of the Earth's rotation (Bell, J.F., 1996; Kaspi V.M; Lorimer D., 2008)

The StarFire system uses a network of more than 50 GPS reference stations around the world to compute GPS-satellite orbit and

clock corrections. These corrections are broadcast via three geosynchronous satellites to the GPS receiver, enabling precise real-time navigation without the need for a ground base station.