FIGURE 1 The current GNSS augmentation technologies.
ANALYSIS OF GNSS AUGMENTATION GOALS AND OBJECTS
The goal of GNSS augmentation is to meet the improved performance requirements of the high-level user. GNSS navigation performance requirements defined by the International Civil Aviation Organization (ICAO) and the Radio Technical Commission for Aeronautics (RTCA) are shown in Tables 3 and 4.
The above tables show that the accuracy, integrity, continuity, and availability requirements are different in different flight phases. The accuracy requirement can be met easily, but the integrity, continuity, and availability requirements are stringent and cannot be provided by the current GNSS.
In addition, some high-level users have required decimeter and centimeter positioning accuracy, and these requirements cannot be provided by the current GNSS either.
The objects of augmentation are to allow the basic GNSS, including GPSII, modernized GPS, GLONASS, Galileo, COMPASS regional system and GPSIII, modernized GLONASS, Galileo+, and COMPASS global system, to meet positioning, navigation, and timing service requirements.
The constellation, user range error (URE) performance, and integrity monitoring performance are different for different GNSS and for their different construction stages. So the accuracy, integrity, continuity, and availability performance are at different levels (Table 5).
The goals of augmentation show the accuracy requirements of augmentation can be divided into two classes: 1 m level and <1 m level (including decimeter