l. Introduce of PPP（Precise Point Positioning）

Currently, Real-Time Kinematic (RTK) and Precise Point Positioning (PPP) technologies are the most widely and deeply researched technologies for high-precision positioning based on GNSS. RTK technology offers high accuracy, fast convergence, and good dynamic performance. However, it is limited by factors such as baseline length and network availability, and it can be relatively expensive. On the other hand, PPP technology, although slower in convergence compared to RTK, only requires a single receiver for positioning, is not limited by the operational range, and has lower costs. Furthermore, with continuous technological advancements, the accuracy level of PPP has reached a comparable level to RTK. Therefore, PPP has become the preferred choice for high-precision positioning in non-differential environments.
      
Gintec has implemented Unicore's PPP GAP technology, which reutilizes the UM980 board's high-precision, full-system and full-frequency observation data. Through various combinations of observation data, the convergence time of PPP is accelerated by 50%. After the PPP ambiguity is resolved, if a satellite loses lock, this technology can repair cycle slips for all satellites by utilizing unique ionospheric and tropospheric error models after satellite signalsrecover,achieving single-epoch ambiguity convergence. This significantly reduces the time required for ambiguity re-convergence,  improving the availability of PPP.

After continuous testing and upgrading, Gintec's G40 receiver currently supports the two latest PPP technologies in the world, namely BDS PPP and Galileo Has, and both are freely available to all users. The differences between these two technologies are as follows:

1. BDS PPP (BeiDou Satellite System Precise Point Positioning): It is achieved through the broadcast of the BDS-3 satellite system, covering China and its surrounding regions. The convergence time for this technology is 10-15 minutes, providing sub-meter-level accuracy.

2. Galieo Has, achieved through the broadcast of Galileo E6-B satellites, offers two kinds of service:
(1)Within Europe: horizontal accuracy＜ 20cm, vertical accuracy＜ 40cm, convergence time＜ 100s.
(2)Global coverage: horizontal accuracy＜ 20cm, vertical accuracy＜ 40cm, convergence time＜ 300s.

In addition, by using PPP-RTK technology, the G40 receiver can maintain high-precision positioning through PPP after the RTK correction has failed, and with RTK after the PPP precision data has failed. Moreover, RTK can speed up PPP, and PPP can also speed up RTK ambiguity fixing. All subsequent kinds of RTK produced by the Gintec team (such as G40P) will also retain this feature.

ll. Operation Guide

Before using the PPP function, ensure that：
a）the device firmware version is 1.0.240322.1 or later.
b）the board firmware version is  R4.10Build11833 or later.

i. When there is no differential data
1. Connect to the WEBUI, open "Enable BDS" and "BDS PPP" or "Enable GALILEO" and "GALILEO HAS".

2. Place the instrument in an open field to receive the satellite signal, and wait 10-20 minutes until it gets "PPP FIXED". Now you can start using it.

ii. When there is differential data
1.Connect to the WEBUI, open "Enable BDS" and "BDS PPP" or "Enable GALILEO" and "GALILEO HAS".
2.Please set up the rover and get to work as you would for a normal surveying operation. 
3.When you lose the differential data from the base station or CORS in some special circumstances (e.g. the radio signal received interference), G40 will jump directly from Fixed state to PPPFIXED state, so you can continue to work without interference.

Note: In the whole process, it is necessary to ensure the host can always receive the satellite signal normally, otherwise the convergence may need to be re-performed after the loss of the signal.

Written by:   Jenny Ye                                                                    Translated by: Madelyn Ma                                                                  Proofread by: Wyatt Bai