How to choose a GNSS receiver suitable for slope monitoring?

The stability of slopes is a key factor affecting the driving safety and maintenance costs of highways. Slope monitoring is crucial for ensuring geological safety along highways, requiring the ability to obtain relevant data in real-time, accurately, and stably.Global Navigation Satellite System (GNSS) technology has become the mainstream technical means in the field of slope deformation monitoring due to its outstanding advantages of high precision, all-weather and continuous monitoring.In this paper, we will combine the main principles of GNSS technology to deeply analyze the actual needs of highway slope monitoring, and formulate a reasonable GNSS terminal selection strategy.

1、Principles of GNSS and Its Application in Slope Monitoring

GNSSreceivers mainly rely on high-precision real-time dynamic positioning technology (RTK) or carrier phase difference technology, which can achieve real-time deformation monitoring at the sub-centimeter level, so as to meet the accurate grasp of slope displacement and deformation rate. Compared with traditional measurement methods, GNSS monitoring has the advantages of no line of sight, continuous data and a high degree of automation, which is suitable for monitoring complex environments and remote areas.

Taking the NJ-iot610 GNSS receiver as an example, its multi-frequency and multi-mode technology can receive multi-system and multi-frequency signals such as GPS and Beidou at the same time, which significantly improves the accuracy, reliability and anti-interference ability of positioning. In slope monitoring, GNSS technology can provide high-precision positioning data, detect small deformationsof slope in time, and provide key data support for slope stability assessment and early warning.

2、Demand Analysis for GNSS Receivers in Slope Monitoring

（1）High-precision positioning

Slope deformation is usually in the order of millimeters to centimeters, which requires GNSS equipment to have high-precision real-time positioning capabilities, and the commonly used RTK technology to achieve sub-centimeter-level precision positioning accuracy needs to achieve plane accuracy of ±(2.5 1×10⁻ ⁶×D) mm, and elevation accuracy of ±(5 1×10⁻ ⁶×D) mm, to meet the needs of high-precision displacement monitoring.

（2）Multi-system and multi-frequency compatibility

In order to ensure that more than 6 satellites can be continuously locked in the environment of mountains on both sides of the slope, it must support GPS (L1/L2/L5), Beidou (B1/B2/B3), GLONASS (L1/L2) and Galileo (E1/E5a/E5b) and other multi-system and multi-frequency signal reception.

（3）Intelligent anti-interference ability

Complex electromagnetic interference such as on-board radar and mobile base stations in highway environments. GNSS receivers need to be equipped with anti-multipath algorithms (such as narrow correlation technology) and electromagnetic filtering functions to effectively deal with complex electromagnetic interference and ensure the accuracy and reliability of positioning data.

（4）Stable data transmission

Slope monitoring needs to obtain data in real time, and the GNSS receiver should support redundant transmission of dual-SIM 4G/5G networks, with breakpoint resumable transmission and local storage functions. This not only ensures the real-time upload of data, but also stores data in the event of a network failure, and continues to transmit it after the network is restored, ensuring the integrity and continuity of monitoring data.

（5）Industrial-grade protection design

The geological monitoring environment is harsh, and the GNSS receiver needs to have IP68 protection level, adapt to the working temperature range of -40°C~ 75°C, and have a built-in lightning protection module with 15kV air discharge protection to ensure the stable operation of the equipment under various harsh conditions.

（6）Expand integration capabilities

Equipped with RS485, CAN bus, IO trigger and other interfaces, it supports an integrated monitoring system with inclinometer, rain gauge, crack meter and other sensors.

3、Selection of GNSS Receivers（NJ-iot601）

（1）Introduction to the equipment that can add 4G GNSS displacement receiver:
Nengjia's GNSS displacement receiver is a high-precision, low-power displacement monitoring device, which integrates satellite antennas, GNSS boards, 4G communication modules and SIM cards, and adopts an integrated design to simplify on-site installation and construction. The device integrates advanced GNSS positioning technology and stable 4G communication technology, which can obtain the displacement data of the monitored target in real time and accurately, and quickly upload it to the background monitoring system through the 4G network.

The device supports remote configuration and firmware upgrade, has a built-in 6-axis attitude angle sensor, has an automatic calibration function, and is suitable for the access of various sensors such as meteorology, environment, and water conditions, and is widely used in geological disaster monitoring, engineering safety monitoring and other fields. It provides reliable data support for geological disaster early warning, building structure safety monitoring, mining monitoring and many other fields.

（2）Performance characteristics

Remote configuration and management:Support remote modification of upload frequency, firmware upgrade, power supply status and terminal equipment status calling, reducing on-site construction and maintenance costs.

Low-power design:The average power consumption of the whole machine is within 2W, which is suitable for long-term field monitoring to reduce energy consumption and equipment replacement frequency.

Multi-sensor access:support the access of meteorological, environmental, water condition and other sensors, and expand the monitoring function.

Battery status monitoring:real-time monitoring of the remaining power and charging and discharging of the external battery, and transmit the data to the background, so as to understand the battery status in time and ensure the continuous operation of the equipment.

High-precision positioning:plane accuracy ± (2.5 1×10⁻⁶×D) mm, elevation accuracy ± (5 1×10⁻⁶×D) mm, to meet the requirements of high-precision displacement monitoring, to provide accurate deformation data.

Automatic calibration:Built-in 6-axis attitude angle sensor, automatic calibration after power-on to ensure measurement accuracy.

（3）NengjiaGNSS cloud platform

The GNSS cloud platform is a cloud-based intelligent system designed for high-precision displacement monitoring and geological disaster early warning, integrating multi-mode satellite signal reception, AI solution model and digital twin technology to build a three-level architecture of "perception layer-cloud layer-application layer", supporting millimeter-level displacement monitoring, multi-source data fusion and three-dimensional dynamic simulation. Its core calculates three-dimensional coordinates in real time through satellite signals such as Beidou/GPS, and establishes disaster prediction models based on meteorological and geological sensor data, which are applied to slope stability analysis, water conservancy engineering safety monitoring and other fields, and supports the hybrid deployment of private cloud and public cloud to achieve hierarchical data management.

1.Remotely upgrade the firmware through the 4G network to ensure the continuous update of device performance and security.

2.Support real-time remote monitoring, users can check the status of the equipment at any time to ensure the accuracy of displacement data.

3.Support remote modification of upload frequency, power supply status and terminal equipment status calling, reducing on-site construction and maintenance costs.

4.Support the access of meteorological, environmental, water condition and other sensors, and expand the monitoring function.

5.The average power consumption of the whole machine is within 2W, which is suitable for long-term field monitoring.

6.Real-time monitoring of the remaining power and charging and discharging of the external battery.

Slope and geological monitoring have high requirements for the accuracy, reliability and stability of GNSS receivers. Combined with the principle of GNSS technology, the receiver suitable for monitoring should have multi-frequency and multi-mode, high-precision RTK positioning, strong anti-interference and multi-path rejection capabilities, and support stable real-time data transmission and long-term outdoor use. Through reasonable selection, the construction of a slope deformation monitoring system based on GNSS can effectively improve the early warning ability of geological disasters along the highway and ensure traffic safety and stable operation of the project.