26 Dec High quality GNSS with various positioning techniques
Autonomous mode is a basic method of GNSS positioning, also known as standalone, absolute or SINGLE mode for Position, Velocity, Time (PVT) calculation. While using this method, the PVT (navigation solution) is obtained without usage of any external data (sources of augmentation or correction).
So, autonomous GNSS does not depend on receiving data via secondary data channels, and from this point of view, is reliable and more accessible.
SBAS mode allows improved the performance of GNSS receivers by regional Satellite Based Augmentation Systems (WAAS, EGNOS, GAGAN, MSAS, SDCM and other SBAS-compatible services).
PPP mode is a high accurate positioning mode. Current version of RTCM-SSR corrections supports so-called floating PPP, i.e. PPP with float ambiguities. The typical convergence time is between 20-35 minutes. PPP mode requires the use of dual-frequency measurements for estimation ionospheric delay, thus the use of dual-frequency antennas is a must for using PPP mode. The PPP convergence time depends on the quality of SSR corrections, satellite geometry, atmospheric conditions. The current version of RTCM SC-104 standard supports only GPS and GLONASS navigation systems.
RTK rover mode is a differential positioning mode that requires a set of measurements received from the reference station (base station). Building the differences of measurements between the rover receiver and the reference station allows the rover receiver to effectively decrease the influence of the delays associated with ionosphere and troposphere as well as to get rid of the error related to satellite clocks. The position accuracy achievable by the receiver(s) depends on the baseline length, quality of GNSS measurements received from the reference station, atmospheric conditions, multipath environment etc.
RTK base mode assumes generation of GNSS measurements along with information about coordinates of the reference station and antenna type. In RTK base mode, the reference station generates the following RTCM messages: MSM7, 1005/1006, 1007/1008, 1230.