The Prediction of Geocentric Corrections during Communication Link Outages in PPP

Abstract

The International GNSS Service (IGS) real-time service (RTS) provides access to real-time precise products. State-Space Representation (SSR) products are disseminated through the Internet using the Networked Transport of the RTCM (Radio Technical Commission for Maritime Services) via the Internet Protocol (NTRIP). However, communication outages caused by a loss of the communication link during ephemeris changes can occur. Unfortunately, any break in providing orbit and clock corrections affects the possibility to perform precise point positioning. To eliminate this problem, various methods have been developed and presented in the literature. The solution proposed by the authors is to directly predict geocentric corrections. This manuscript presents the results and analysis of geocentric correction predictions under two scenarios: the first between the IODE (issue of data ephemeris) value change and the second where prediction must be done for epochs containing a change in IODE ephemeris. In this case, the prediction uses data from a previous message. The Root Mean Square (RMS) values calculated based on the differences between the true correction values and the predicted geocentric corrections using a linear function, a second-degree polynomial and a constant value do not differ significantly. The numerical results show that, in most cases, maintaining the constant value of the last registered SSR correction is the best option.

Keywords: GNSS; SSR orbit corrections; prediction.

Figure 1

The interpretation of space-state representation (SSR) orbit corrections.

Figure 2

Time series of the geocentric corrections δP of DOY 99, GPS 13.

Figure 3

Time series of the geocentric corrections δP of DOY 85, GPS 28.

Figure 4

Time series of the geocentric corrections δP of DOY 102, GPS 30.

Figure 5

The results of the δX geocentric correction extrapolation (GPS G13) for a 70 min data-stream—the time series of orbit corrections refer to an out-of-date navigation message.

Figure 6

The results of the δY geocentric correction extrapolation (GPS G13) for a 70 min data-stream—the time series of the orbit corrections refer to an out-of-date navigation message.

Figure 7

The results of the δZ geocentric correction extrapolation (GPS G13) for a 70 min data-stream—the time series of the orbit corrections refer to an out-of-date navigation message.

Figure 8

The results of the δX geocentric correction extrapolation (GPS G13) for a 15 min data-stream—The time series of the orbit corrections refer to an out-of-date navigation message.

Figure 9

The results of the δY geocentric correction extrapolation (GPS G13) for a 15 min data-stream—The time series of the orbit corrections refer to an out-of-date navigation message.

Figure 10

The results of the δZ geocentric corrections extrapolation (GPS G13) for a 15 min data-stream—the time series of the orbit corrections refer to an out-of-date navigation message.

Figure 11

The results of the δX geocentric correction extrapolation (GPS G28) for a 60-min data-stream between each issue of data ephemeris (IODE).

Figure 12

The results of δY geocentric correction extrapolation (GPS G28) for a 60-min data-stream between each IODE.

Figure 13

The results of the δZ geocentric correction extrapolation (GPS G28) for a 60-min data-stream between each IODE.

Figure 14

The results of the δX geocentric correction extrapolation (GPS G28) for a 15-min data-stream between each IODE.

Figure 15

The results of the δY geocentric correction extrapolation (GPS G28) for a 15-min data-stream between each IODE.

Figure 16

The results of the δZ geocentric correction extrapolation (GPS G28) for a 15-min data-stream between each IODE.

Figure 17

Influence of degrading orbital corrections on PPP results.