Why GNSS Positioning Errors Occur and How Correction Technologies Improve Accuracy in Real Applications

Diagram showing GNSS signal transmission from satellites to a ground receiver with labeled error sources such as atmospheric delay and multipath.

Global Navigation Satellite Systems (GNSS) enable positioning by calculating distances between user receivers and satellites. While the theoretical process is straightforward, real-world environments introduce multiple sources of error that reduce accuracy. Understanding these error mechanisms—and how correction systems compensate for them—is essential for applications requiring reliable positioning.

Why GNSS Positioning Is Not Always Accurate

GNSS signals travel approximately 20,000 km from satellites to Earth. During this transmission, the signals are affected by atmospheric conditions, environmental obstructions, and receiver limitations. As a result, raw positioning accuracy typically ranges within several meters.

Key Factors Causing GNSS Errors:

1.Satellite Geometry

The relative distribution of satellites affects the quality of the positioning solution. Poor geometry increases dilution of precision (DOP), reducing accuracy.

2. Atmospheric Delay

Signals passing through the ionosphere and troposphere experience speed variations, introducing distance estimation errors.

3. Multipath Effects

Signals may reflect off buildings, water, or terrain before reaching the receiver, creating distorted or delayed measurements.

4.Receiver Noise

Hardware limitations, algorithm performance, and antenna characteristics also contribute to measurement deviation.

These factors collectively lead to positioning offsets, even when satellites are functioning normally.

Graphic categorizing GNSS errors into satellite, atmospheric, environmental, and receiver-related sources.

Types of GNSS Errors

GNSS errors are typically categorized into:

● Satellite-related errors (20%–40%)

Orbit prediction deviations and satellite clock drift.

● Propagation errors (20%–30%)

Atmospheric effects such as ionospheric and tropospheric delay.

● Environmental errors (20%–30%)

Multipath, signal blockage, and surrounding terrain or urban structures.

● Receiver-related errors

Antenna performance, internal noise, and data processing strategies.

Understanding these categories helps determine which correction method is required in each application.

How Correction Technologies Minimize GNSS Errors

To restore high-precision positioning, GNSS systems integrate correction models and reference stations that compensate for deviations caused during signal transmission.

1. SBAS (Satellite-Based Augmentation System)

Provides wide-area corrections via geostationary satellites.
Suitable for aviation, general navigation, and medium-accuracy applications.

2.PPP (Precise Point Positioning)

Uses precise satellite orbit and clock corrections.
Provides decimeter-level accuracy without local base stations.
Ideal for marine operations, surveying, and high-precision mapping where stable performance is required.

3.RTK (Real-Time Kinematic)

Uses a local reference station to deliver real-time correction data, enabling centimeter-level accuracy.
Widely used in agriculture, UAVs, robotics, and engineering applications requiring rapid convergence and high stability.

A comparison of these methods shows that each correction solution offers different levels of accuracy and convergence time. Selecting the appropriate approach depends on environmental constraints and performance requirements.

How to Choose the Most Suitable Correction Method

Different application scenarios require different levels of precision:

● Navigation and general positioning: SBAS provides a balance of coverage and accuracy.

● High-precision tasks such as surveying and inspection: RTK delivers fast, centimeter-level results.

● Large-scale or remote operations: PPP offers stable accuracy without reliance on local base stations.

● Robotics, autonomous vehicles, and precision agriculture: RTK or network RTK services remain the preferred choice due to real-time performance.

By understanding the origin of positioning errors and selecting an appropriate correction system, GNSS accuracy can be improved significantly to meet the needs of advanced applications.

Why GNSS Positioning Becomes Inaccurate and How Correction Methods Restore Precision