DP-filter Smooth Technology: Pass to Pass Solution for Agricultural Guidance Systems

GNSS receivers operating in the single-point autonomous mode offer a horizontal accuracy of around 1.5 meters. While this might sound precise, it often experiences significant drift due to pseudorange accuracy inconsistencies and a lack of correction inputs during positioning calculations. In specific applications, like agricultural guidance systems, it isn't the absolute accuracy that counts but the relative precision across continuous epochs and adjacent paths. Discontinuities, even minor ones, can be highly problematic for users.


Enter ComNav Technology's DP-filter, a state-of-the-art smoothing filter algorithm that leverages carrier phase, delta-carrier phase, pseudorange, and Doppler observations. This article dives into the DP-filter's technical underpinnings, configuration, tested results, and its potential application scenarios.


Fig. 1 Pass to Pass

1. Technical Introduction

Carrier phases offer superior accuracy, reduced noise, and increased resistance to multipath effects. Drawing from these advantages, the DP-filter refines relative positioning precision, ensuring smooth and consistent outcomes unaffected by pseudorange inaccuracies. When engaged, this filter delivers consistent position error and assures a smooth (pass to pass) accuracy within the sub-meter to centimeter range.

2. Smooth Mode configuration

Here shows how to enable the Smooth mode for SinoGNSS K8 series OEM modules.


2.1. Activating the Smooth Mode

● Enable the feature: Begin by sending the command `Set smoothedpvt on`. This instruction activates the smooth mode.

●Save the configuration: Once you've activated the mode, make sure you save the configuration. Do this by sending the command `Saveconfig`.


Fig. 2 Activating the Smooth Mode

Note: If you wish to deactivate the Smooth Mode later on, simply send the command `set smoothedpvt off`.


2.2. Verifying the Smooth Mode Activation

To check if your OEM board is operating in the smooth mode:

● Output the `GPGGA` message.

● In the displayed message, inspect the solution status. If it reads `E,1`. Moreover, the differential age value should be `99`. It indicates that the board is in smooth mode.

For instance, the message should resemble the following format: 

`$GPGGA,000359.00,3125.4999742,N,12136.9969461,E,1,07,2.5,10.4541,M,11.371,M,99,00 00*4C`


Fig. 3 Verifying the Smooth Mode Activation

3. Test Results

ComNav Technology conducted tests on the DP-filter smoothing function of the K803 Lite module. The results provided insights into the DP-filter smooth function's performance and applications.


3.1. Test Methodology

- Environment: The test was done at roof of ComNav Technology's building to minimize interference from obstacles.


Fig. 4 Testing route on Google Earth map

- Procedure:

  - The GNSS modules and antenna were installed on a trolley.

  - The trolley was pushed repeatedly along a straight line in a consistent direction.

  - The accuracy of the K803 Lite was measured by comparing its multiple trajectories and contrasting with RTK trajectories.


Fig. 5 Testing route


3.2. Test Findings:

- This test simulated conditions in areas without BDS-2 coverage.

- The pass-to-pass accuracy for the K803 single-frequency was about 15cm.

- No significant track deviation was observed across 31 laps.

- The final trajectory deviation from the RTK track was 10cm.


Fig. 6 Test trajectory of K803 Lite (K803 Lite-Red,RTK-blue)

Note: As DP-filter provides relative positioning result, we shifted the trajectory based on the start location of RTK, for better check DP-filter performance.

4. Application Scenarios of the DP-filter

The DP-filter is particularly valuable in scenarios requiring high relative position precision and consistent performance. One such application is in agricultural guidance systems. Ensuring a tractor or harvester remains on a consistent path, unaffected by GNSS drifts, can translate to substantial savings and increased operational efficiency for farmers.


Fig. 7 Precision Agriculture


Reduced GNSS Drifts: Tractors, harvesters, and other agricultural machinery equipped with DP-filter can benefit from reduced GNSS drifts. GNSS drifts, a common challenge, can cause machinery to deviate from its designated path, leading to uneven seeding or wasteful overlaps during crop treatment. By ensuring that these machines adhere to a consistent trajectory, the DP-filter can significantly reduce operational inefficiencies.

Substantial Savings: Precision agriculture, with the help of tools like the DP-filter, can translate into considerable cost savings for farmers. Fewer resources are wasted, there's reduced wear and tear on machinery due to fewer unnecessary passes, and crops can be managed more effectively, leading to higher yields.

Optimized Resource Use: When machinery follows the exact path without deviations, there's optimal utilization of water, fertilizers, and other inputs, which not only saves costs but also promotes sustainable farming practices.

5. Conclusion

SinoGNSS K-series OEM boards provide reliable pass-to-pass performance, making it a low cost GNSS module for applications especially for precision agriculture, as it requires no correction input and internet access. For more information of our GNSS modules/GNSS boards/GNSS receivers, you can visit our website by this link:




About ComNav Technology

ComNav Technology is the major provider of GNSS OEM boards, receivers and high precision positioning solutions, encompassing product development, and marketing. Its technology and products have already been applied in a wide range of fields such as surveying, construction, machine control, agriculture, intelligent transportation, precise timing, deformation monitoring, and unmanned system. With its experienced team and innovational spirit, ComNav Technology is always trying best to provide reliable and competitive products to global customers. ComNav Technology has been listed on the Shanghai Stock Exchange (Science and Technology Board), securities :ComNav Technology (Compass Navigation), Stock code: 688592.

About SinoGNSS®

SinoGNSS® is the official trademark of ComNav Technology Ltd., registered in People’s Republic of China, EU, USA and Canada. All other trademarks are the property of their respective owners.


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