What is the accuracy difference between Fixed and Float RTK?

Fixed RTK typically delivers ±8 mm horizontal and ±15 mm vertical accuracy. Float RTK carries ±300–1000 mm of positioning error depending on baseline length and atmospheric conditions.

Why does my RTK show Fixed but coordinates are still wrong?

Common causes are a datum mismatch (wrong coordinate system), an incorrect geoid model applied to elevation, or an antenna height entry error.

How do I know if multipath is affecting my survey?

Multipath typically shows as unstable repeated measurements — the same physical point measured three times gives results differing by 20–50 mm rather than the expected ±8 mm.

Can I survey during ionospheric storms?

RTK accuracy degrades during geomagnetic storms (Kp index above 5). For precision engineering or cadastral surveys, postpone sessions until the Kp index drops below 3.

What is the maximum reliable CORS baseline for centimetre accuracy?

Most CORS networks guarantee ±10–20 mm horizontal accuracy within 50 km of the nearest reference station. Beyond 70 km, deploy a self‑deployed base station within 15 km of the survey area.

APEKS FAQ | Understanding CORS: The Technology Behind Precise RTK Positioning

2025-08-22

Understanding CORS: The Technology Behind Precise RTK Positioning

If you're interested in high-precision positioning or RTK surveying, you may have heard of CORS (Continuous Operational Reference System). But what exactly is it, and how does it improve positioning accuracy? This article will explain CORS in a simple and intuitive way.

What is CORS?

CORS stands for Continuous Operational Reference System.

Think of it as a nationwide network of GNSS base stations that operate 24/7, providing high-precision positioning services. By purchasing an account, users can access the network anytime for accurate location data.

How Does CORS Work?

Most modern CORS networks use the VRS (Virtual Reference Station) algorithm.

The core idea is that instead of relying on a single base station, the system combines data from multiple stations. This allows it to correct for various systematic errors, including:

Atmospheric refraction
Ionospheric delay
Clock biases
Satellite orbit errors

Limitations of Traditional RTK

In traditional RTK surveying, accuracy depends heavily on the distance (D) between the rover and the base station.
The formula is usually:

±1 cm + 1 ppm × D

This means that the farther away the rover is from the base station, the larger the error.

How CORS Solves the Accuracy Problem

CORS performs network-wide calculations and creates a virtual base station right next to the rover, making the “1 ppm × D” term nearly zero.

The result: centimeter-level accuracy anywhere within the coverage area.

Other CORS Services

Besides high-precision RTK, CORS also provides pseudorange differential corrections, offering sub-meter positioning accuracy.

This enables precise positioning for vehicles, ships, and even smartphones.

Conclusion

CORS has made high-precision positioning easier and more reliable.

For professional surveyors, it ensures efficiency and measurement accuracy.
For general applications, such as smart transportation and navigation, it enables sub-meter positioning precision.

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