These days any vessel undertaking an ocean or coastal navigation passage would almost certainly be using a marine GPS which would be interfaced with other electronic devices such as Radar, Automatic Identification Systems (AIS) and Digital Selective Calling (DSC) marine radios.
A marine Global Positioning System (GPS) works by utilizing a network of satellites to determine the precise location of a GPS receiver on a vessel. Here’s a breakdown of how a marine GPS works:
- Satellite Constellation:
- The GPS system consists of a constellation of satellites orbiting the Earth. As of my last knowledge update in January 2022, the GPS constellation includes at least 24 satellites, distributed across multiple orbital planes.
- Satellite Signals:
- Each GPS satellite broadcasts signals containing information about its location and the current time. These signals are transmitted using radio waves in the microwave frequency range.
- GPS Receiver:
- A GPS receiver is a device on the vessel that picks up signals from multiple GPS satellites. The receiver contains a specialized chipset that processes these signals.
- Trilateration:
- The GPS receiver uses a process called trilateration to determine its precise location. Trilateration involves measuring the distance from the receiver to at least three satellites in the GPS constellation.
- Calculation of Position:
- The GPS receiver calculates its position by analysing the time it took for the signals to travel from the satellites to the receiver. Since the signals travel at the speed of light, the GPS receiver can use the time delay to calculate the distance to each satellite.
- Satellite Geometry:
- The accuracy of the GPS position is influenced by the geometry of the satellites in view. A better satellite geometry (wider separation between satellites) generally results in more accurate position calculations.
- Correction Signals (Optional):
- In some marine applications, especially those requiring high precision, correction signals may be used. These correction signals provide additional data to enhance the accuracy of the GPS position.
- Display and Navigation:
- The calculated position information is then displayed on a navigation device, such as a chart plotter or GPS chart plotter, showing the vessel’s latitude, longitude. The display may also show other information like speed, course, and time.
- Integration with Navigation Systems:
- GPS receivers on marine vessels are often integrated into broader navigation systems. These systems may include additional sensors, such as radar, sonar, electronic charts, Automatic Identification Systems (AIS) and Digital Selective Calling (DSC) marine radios providing a comprehensive navigation solution.
- Updates and Real-Time Positioning:
- The GPS receiver continuously updates the vessel’s position in real-time as long as it has a clear line of sight to a sufficient number of GPS satellites.
- Redundancy and Reliability:
- GPS systems are designed with redundancy to ensure reliability. Even if some satellites are unavailable due to maintenance or other issues, the system can still provide accurate positioning.
It’s important to note that while GPS is a powerful and widely used navigation tool, it does have limitations. Factors such as signal blockage by tall buildings or natural obstacles, atmospheric conditions, and intentional interference can affect the accuracy of GPS readings. Additionally, advancements in technology may have occurred since my last update in January 2022. Always refer to the latest information and user manuals for the most accurate and up-to-date details on GPS technology.
For more Coastal Navigation information please go to our website at: Coastal Navigation..It’s Easy
For Coastal Navigation course enrolments please use this link: Coastal Navigation Enrolments