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3. Signals of GNSS

This chapter discusses the Global Navigation Satellite Systems (GNSS) and their operational principles, highlighting the various signals transmitted by satellites, the advantages and disadvantages of GNSS technology, and the types of GNSS receivers available. The chapter explores surveying techniques using GNSS, including static, kinematic, and real-time kinematic methods, along with their respective pros and cons. Additionally, the role of augmentation systems like WAAS and MSAS in enhancing GNSS accuracy is outlined.

Sections

Signals of GNSS

This section explains the key signals used in the Global Navigation Satellite System (GNSS), including L1, L2, and L5 frequencies, and their applications in both military and civilian contexts.

3.4.4 Section Overview

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Advantages and disadvantages of GNSS

This section outlines the key advantages and disadvantages of Global Navigation Satellite Systems (GNSS), emphasizing their benefits in navigation and positioning, as well as their limitations in various environments.

3.4.5 Section Overview

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3.4.5.1 Advantages

GNSS provides a range of advantages, including ease of navigation, global availability, and independence from weather and visibility conditions.

3.4.5.2 Disadvantages

This section highlights the key disadvantages of GNSS technology.

Types of GNSS receivers

This section details the various types of GNSS receivers, including their applications and accuracy levels.

3.4.6 Section Overview

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3.4.6.1 Navigation receivers

Navigation receivers are devices used for various applications including personal and vehicular navigation, offering varying degrees of positional accuracy.

3.4.6.2 Surveying receivers

Surveying receivers are specialized GNSS devices designed to achieve high accuracy for various surveying applications.

3.4.6.3 Geodetic receivers

Geodetic receivers are advanced GNSS devices designed for high-precision applications, using multiple frequency signals to achieve centimeter-level accuracy.

3.4.6.3.1 Code phase receivers

Code phase receivers utilize GNSS P- or C/A-code signals for navigation and positioning, allowing them to determine location without prior knowledge of coordinates.

3.4.6.3.2 Carrier phase receivers

Carrier phase receivers utilize GNSS signals to provide precise positioning through direct measurement of the signal phase changes.

Working of a GNSS

This section explains the operational principles of Global Navigation Satellite Systems (GNSS), focusing on how satellites use signals to determine accurate locations through trilateration.

3.4.7 Section Overview

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3.4.7.1 Trilateration

Trilateration is a positioning method used by GNSS systems that determines the location of a receiver based on distances from multiple satellites.

GNSS surveying techniques

This section discusses various GNSS surveying techniques, particularly focusing on static, rapid static, kinematic, and real-time kinematic approaches.

3.4.8 Section Overview

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3.4.8.1 Static surveying

Static surveying is a GNSS technique that ensures high accuracy by continuously collecting data over a set period at defined locations.

3.4.8.2 Rapid static surveying

Rapid static surveying is an efficient GNSS surveying method that allows for quick and accurate measurements, particularly suitable for short-range applications.

3.4.8.3 Kinematic surveying

Kinematic surveying involves using differential carrier phase tracking to obtain precise location data for surveying applications.

3.4.8.4 Stop and go kinematic surveying

This section discusses the stop and go kinematic surveying technique used in GNSS, focusing on its methodology and applications.

3.4.8.5 Real-time kinematic (RTK) surveying

RTK surveying is a technique that allows for real-time, highly accurate positioning using GNSS data by employing a stationary base station and one or more roving receivers.

3.4.8.6 Pseudo-kinematic surveying

Pseudo-kinematic surveying combines static and kinematic techniques to effectively collect GNSS data in challenging environments.

3.4.8.7 Differential GNSS (DGNSS) surveying

Differential GNSS (DGNSS) surveying enhances the accuracy of standard GNSS by using two GNSS units: a reference (known location) and a rover (unknown location) to calculate differential corrections.

Other satellite-based augmentation systems (SBAS)

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3.4.9 Section Overview

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3.4.9.1 Wide Area Augmentation System (WAAS) survey

The Wide Area Augmentation System (WAAS) significantly improves GPS accuracy and reliability for navigation by providing correction signals.

3.4.9.2 MSAS Japan

The MSAS (MTSAT Satellite-based Augmentation System) enhances the accuracy and reliability of GPS signals in Japan.

Learning Objectives

  • GNSS operates using various signals (L1, L2, L5) to provide navigation data.

  • Different types of GNSS receivers are suitable for various applications such as navigation, surveying, and geodesy.

  • The positioning accuracy of GNSS depends on multiple factors including satellite visibility, and the use of correction techniques can significantly improve precision.

Key Concepts

Pseudo Random Code (PRC)

A random sequence sent from GNSS satellites, allowing synchronization between satellites and receivers.

Trilateration

The method used by GNSS receivers to calculate their position based on the distances from three or more satellites.

Differential GNSS (DGNSS)

Technique using corrections from a stationary reference station to improve the accuracy of GNSS measurements.

Real-Time Kinematic (RTK)

A surveying method that provides high-precision positioning in real-time using carrier phase measurements.

Practice Exercises

Total Questions

2

Estimated Time

4 min

Passing Score

70%

Instructions

  • Read each question carefully
  • You can use hints if you need help
  • Complete all questions before submitting
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