K803 Lite (L1) GNSS Module DP-filter Smooth Function Test Report

ComNav Technology conducted a simple test on the DP-filter smoothing function of the K803 Lite (L1) module. This report introduces the DP-filter smooth positioning performance of K803 Lite (L1) based on the theoretical basis and test results, aiming to help users have a clear knowledge of DP-filter smooth function and related applications.

    1 Theoretical Basis

1.1 DP-filter smooth function

The DP-filter smooth algorithm is based on the raw data of GNSS signal carrier phase and Doppler observations. When receiving and measuring the carrier phase, the GNSS receiver is measuring the rate of phase change at the same time, which is also called Doppler frequency shift. Using this observation, it is easy to achieve high velocity accuracy via the double-difference technique and also avoid the difficulty of determining the integer ambiguity.

 

Theoretically, the velocity accuracy of the moving carriers calculated via Doppler frequency shift can reach 1cm/s, which is ideal for some dynamic applications. Benefit from the DP-filter smooth algorithm, the K803 Lite(L1) module largely reduces the sudden position jumps, providing a smooth and relatively accurate positioning trajectory without GNSS correction data input (single-point positioning mode).

  

1.2 Pass-to-pass Accuracy

Pass-to-pass accuracy is a relatively positioning accuracy instead of the absolute accuracy, which is mostly used in agriculture. The GNSS navigation system should keep the distance between passes at a certain value, so as to ensure the high land utilization rate without wasting related resources. So the pass-to-pass accuracy plays an important role in evaluating the performance of GNSS devices used in agricultural applications.

 

Fig. 1 Pass to pass

 

Pass-to-pass error is based on the position offset between the desired track spacing and the actual track spacing calculated by GNSS receivers. Over a 15-minute time window, 95% of the pass-to-pass error of K803 Lite (L1) is within 12cm, and the overall error value is within 15cm.
With the help of the DP-filter smooth algorithm, the relative accuracy of K803 Lite (L1) between 2 consecutive epochs is within 1cm in single point positioning mode. For longer periods like 15-30 min, the pass-to-pass accuracy can be kept within 15cm in 95% of the cases.

 

Fig. 2 & Fig. 3 Pass-to-pass accuracy of K803 Lite (L1) Module

 

   

    2 Test Plan

2.1 Test Environment

To avoid the influence of obstacles, the test was conducted on the roof of ComNav Technology building. The DP-filter smooth testing route is shown in Fig. 4.

 

Fig. 4 Testing route on Google Earth map

 

2.2 Test Device

Table 1: Test device information

Device Model	Manufacture	Serial Number	Firmware
K803 Lite (L1) GNSS Module	ComNav Technology	09000053	600A9_a27

 

2.3 Test Method

Install the GNSS boards and antenna on a trolley, the same antenna is connected to K803 Lite (L1) module and other comparison GNSS modules through the power splitter. Push the trolley several times along the same straight line and the same direction on the roof of the company and record the positioning data.

 

Fig. 5 Test Scene

(1)   By comparing the coincidence of multiple trajectories on the straight line to analyze the pass-to-pass accuracy of K803 Lite (L1).

(2)   By comparing the coincidence of DP-filter trajectories and RTK trajectories to analyze the overall accuracy of K803 Lite (L1).

 

The test was conducted for two rounds,

1st round	full constellation tracking	pushed the trolley for 17 laps
2nd round	masked BDS-2 tracking	pushed the trolley for 31 laps

  

 

    3 Test Result

Since the single point accuracy of DP-filter positioning is within 1m. In order to facilitate trajectory comparison and analysis, the following test results have moved the starting point of the DP-filter data to the starting point of RTK data.

  

3.1 Full-constellation Positioning

In the first round of test, the K803 Lite (L1) is able to track GPS, GLONASS, BDS-2, BDS-3 and Galileo.
As shown in Fig. 6 & Fig. 7, the pass-to-pass accuracy of K803 Lite (L1) is about 10cm. There is no obvious track deviation within 17 laps.
In the end, the trajectory deviated from the RTK track by 5cm.

 

 

Fig. 6 & Fig. 7  Round1 test trajectory, K803Lite (L1)-Red, RTK-Green

 

3.2 Masked BDS-2 Positioning

In order to simulate the tracking situation in areas not covered by BDS-2, the BDS-2 satellites of the K803 Lite (L1) module were masked in the second round of testing.
As shown in Fig. 8 & Fig. 9, the pass-to-pass accuracy of K803 single-frequency is about 15cm, which also included the human error when pushing the trolly. There is no obvious track deviation within 31 laps.
In the end, the trajectory deviated from the RTK track by 10cm.

 

Fig. 8 & Fig. 9 Round2 test trajectory, K803Lite (L1)-Red, RTK-Green

 

    4 Conclusion

About ComNav Technology 

ComNav Technology develops and manufactures GNSS OEM boards and receivers for high precision positioning demanded applications. Its technology already been used in a wide range of applications such as surveying, construction, machine control, agriculture, intelligent transportation, precise timing, deformation monitoring, unmanned system. With a team dedicated for the GNSS technology, ComNav Technology is trying its best to supply reliable and competitive products to worldwide customers. ComNav Technology has been listed on the Shanghai Stock Exchange (Science and Technology Board), securities :ComNav Technology (Compass Navigation), Stock code: 688592.

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