Why and how does the tilt compensation RTK solution works?
Min Chen, Tersus GNSS      15 December, 2022

As we know, the position measured by the conventional GNSS receiver is not directly at the target point but at the antenna phase center. The receiver is usually mounted on a pole that needs to be levelled with a circular bubble in RTK surveys. The target position is calculated by subtracting the phase center offset (PCO) and the length of the pole. Although the results are automatically calculated by the software, it takes time to level the pole, and there will be human errors affecting accuracy. Moreover, the pole cannot be centered at some hidden points. So this method limits productivity and accuracy.  

Then came the traditional receiver with tilt measurement, which can measure a point at an angle instead of centering the pole. Its principle is to use the internal electronic compass to calculate the angle and orientation. According to the length of the measuring rod, the ground target point's actual coordinates can be calculated. This method improves measurement efficiency to some extent, but it also has some disadvantages.

The accuracy is not very high:
◆ the calibration steps are complex and time-consuming.
 it’s easily disturbed by magnetic fields.
◆ it is not possible to support the measurement of large angles, which usually can only reach about 15 degrees.

The new RTK Tilt Compensation technology for the Tersus Oscar Receiver perfectly solves all of the above drawbacks.

The Oscar receiver uses an industrial-grade IMU designed specifically for measurement applications and integrates high-precision MEMS sensor to obtain 3D orientation and acceleration in real-time.

Then, with the length of the pole, the phase center coordinate of the receiver is reduced to the target position of the rod tip in real-time through GNSS/INS fusion algorithm. The user only needs to turn on the machine to set the pole height correctly, and the subsequent measurement can be conducted at any angle.

We summarized some characteristics of the Oscar tilt compensation solution as follows.

◆ High precision
The Oscar receiver equipped with a built-in high-precision self-developed board BX40C, which supports multiple constellations and multiple frequencies to improve the continuity and reliability of the RTK solution even in harsh environments. With the high-precision industrial-grade  IMU, the tilt compensation accuracy of 30 degrees can be within 2cm.

◆ Calibration free
The internal IMU is free from magnetic interference, and the efficient GNSS/INS fusion algorithm makes the Oscar tilt function can be quickly and automatically calibrated when turned on.

◆ Support Large Angle
OSCAR receiver has no measurement angle limit. According to our tests, the tilt can normally work under an angle of 60 degrees, and the accuracy is about 2cm.

◆ Long-time tilt enabled
The tilt of other receivers on the market usually become disabled after a few seconds of rest and need to be recalibration, while the tilt enabled status of the Oscar receiver can be maintained for a long time. At an angle of 60 degrees, Oscar tilt can be stationary for 4 minutes without failure. The smaller the Angle, the longer the retention time.

◆ High efficiency
Because Oscar's tilt function is free of calibration, hard to fail and so on. In the actual measurement process, the measurement efficiency has been greatly improved. Compared with the traditional RTK measurement, the efficiency can be increased by about 50%.

◆ Widely used
OSCAR's excellent tilt measurement not only revolutionizes applications such as topology measurement but also allows point cloud data to be collected for use in applications such as 3D modelling. 

About Tersus GNSS Inc.


Tersus GNSS is a leading Global Navigation Satellite System (GNSS) solution provider. Our offerings and services aim to make centimeter-precision positioning affordable for large-scale deployment.

Founded in 2014, we have been pioneers in design and development GNSS RTK products to better cater to the industry’s needs. Our portfolios cover GNSS RTK & PPK OEM boards, David GNSS Receiver, Oscar GNSS Receiver, MatrixRTK [GNSS CORS Systems] and inertial navigation systems.

Designed for ease of use, our solutions support multi-GNSS and provide flexible interfaces for a variety of applications, such as UAVs, surveying, mapping, precision agriculture, lane-level navigation, construction engineering, and deformation monitoring.

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