GPS – who, what, where?

Digital Skipper |27/07, 2021

What is GPS
You've all heard it mentioned more times than you care to admit, but what What is GPS?

GPS stands for Global Positioning System and is run by the US government. The system was originally called Navstar GPS. It is operated by the United States Space Force (USSF). The GPS system is a satellite-based radio navigation system (RNSS) and is one of the Global Navigation Satellite Systems (GNSS). Several different systems accumulate together to form GNSS which will be discussed later...

GPS, which currently consists of several active orbital satellites, mostly uses nth satellite navigation system in the world, and simply put, GPS is a navigation system consisting of satellites, receivers and complex calculations to determine location, speed (velocity), and time data. The satellites are positioned and orbit on such that there are usually always at least 6 satellites in view, although this is not possible 100% of the time.
At least 3 satellites are required to provide a position fix, as the location is determined using Trilateration. This differs from triangulation, as trilateration only measures distance, not angles.

First; Trilateration

While only three satellites are required for a position determination, a fourth is used to "validate " data from the other three and improve accuracy. The distance is calculated by measuring the time it takes for the signal to arrive from the satellite by the GPS receiver using the following equation: Time delay of signal * Speed of light = Distance

Of course, for this to be possibly, the GPS receiver must have an internal clock as a way to measure time delay. Unfortunately, the satellites have high precision atomic clocks, while the GPS receivers like your cell phone do not. In the first approximations from the three satellites, the time shift/displacement would be considered zero, but the fourth satellite provides an additional distance measurement, which in turn makes is it possible to calculate an exact time delay. An advantage of this is that the GPS receiver's times are extremely accurate, meaning that when the time is "last on" it will not slip off the time fix. Four satellite position fixes are much more accurate than three satellite fixes.
The fourth satellite can also is used to move the position fix from a 2-dimensional, to a 3-dimensional fix, which gives an equivalent value.

What is GNSS?

strong>
A term that you often see when you look at GPS devices are GNSS. The Global Navigation Satellite System (GNSS) is a combination of several satellite positioning systems. This system includes international systems such as GPS (USA), GLONASS (Russia), Galileo (EU), BeiDou (China), IRNSS (India) and QZSS (Japan).

Äeven if you can see GPS is often mentioned on Because it is the most common system and the most well-known acronym, GPS is part of GNSS. So, what does this mean in terms of receivers and devices?

GPS receivers/devices are different from GNSS receivers/devices. A GPS receiver only works with satellites on The GPS system, while GNSS receivers can work with one or more of the above systems, GPS and GLONASS are the most common.

Typically, GNSS units will always be more accurate on; due to the fact that there are more satellites in view, resulting in greater position and time accuracy. But GNSS units are more expensive and the hardware used is different. GNSS works on a larger frequency range than GPS.

Satellite navigation systems can suffer from several problems that can hinder performance. The main culprits for this are:
Physical obstacles. These are the biggest problem for satellite navigation systems. Mountains, forests, tall buildings can all cause obstacles to the signals, which can result in reflection and signal blocking leading to inaccuracies and miscalculations.
Miscalculations.
Some devices may not have properly configured or maintained hardware, which means that there are numerical errors and accuracy errors, although this is rare.
Bad weather conditions such as storm clouds and solar storms can affect these systems. Ionospheric drift is a major contributor to satellite navigation errors, but this can vary depending on; the density and the time of around the clock.
Satellite entertainment. Occasionally, satellites may be maneuvered or taken offline for maintenance, which may temporarily cause incorrect data. This is more of a problem with independent systems like GPS or GLONASS, rather GNSS.
Artificial/artificial disturbances. Devices such as jammers and rogue devices can cause problems for satellite navigation systems. The current advanced generation of satellite navigation system signals is much less susceptible to interference with better signal protection.
What does this mean for my boat?
Position system is crucial for the safety and operation of a boat. There are twoå main guidance points for having a GPS on board.
Safety
Navigation with other devices on board
GPS data can be a lifesaver when you're out and about; the sea. A main reason for having GPS data is in case of emergency when you need to contact the Coast Guard with your VHF. The VHF can receive position data and use DSC (Digital Selective Calling), which is then sent to the Coast Guard, giving them an accurate position determination for you and your boat. This is a life-saving function and is considered a must on; a båt.

Another reason to have GPS onå your boat is designed for navigation in poor conditions or a dangerous scenario. If the conditions are bad, or you have to navigate home via at night, a GPS unit or chartplotter with GPS function can prove its worth. In addition to this, specific locations can be saved as waypoints. Routes can be created with the help of waypoints. These routes can then be followed by an on-board autopilot, creating a semi-autonomous navigation system. I say semi-autonomous because there are potential hazards such as other boats and rocks that require manual input, as the autopilot alone cannot avoid these.

A less common but excellent reason to use; nda a GPS är alarm. Some GPS/chartplotters give you the ability to set alarms such as anchor alarms. An anchor arm can be set up as a virtual fence around your boat on; a certain distance. Should your boat or anchor drift out of this "barrier", an alarm will sound and display a warning message.
How do our products relate to this?
strong
GPS units are available as both NMEA 0183 and NMEA 2000 products. A common scenario is that the boat has an existing legacy NMEA 0183 GPS, but a NMEA 2000 network complete with MFDs/chartplotters for displaying data. This is our NGW-1 Bi -Directional conversion gateway enters. The NGW-1 will convert the NMEA 0183 sentences sent from your GPS to NMEA 2000 PGN for all devices in your N2K network to see. This is a much more cost-effective solution than replacing your 0183 GPS with a new NMEA 2000 unit.

With technology advancing very quickly, on-board computers and trådlö said devices such as the iPad's regular på a båt. Thankfully, we offer a solution to bring your data to both. If you want NMEA 2000 data from your network to be sent to a PC application such as Maxsea Time Zero, or our own NMEA Reader software, then är NGT-1 NMEA 2000 Gateway the perfect solution. The unit can receive all available PGNs at the moment and transfer this to a NMEA 2000 PC application. Since this device is bi-directional, you can also send NMEA 2000 PGN from the PC application back to the network. Actisense W2K-1 the product you choose här. Our gateway is connected to your NMEA 2000 network so that it can receive any NMEA 2000 PGN. This device can be connected to a peripheral via Wi-Fi, allowing data to be sent and received. Since most mobile apps use NMEA 0183 as the data format, W2K-1 can be used with them because it contains the same conversion engine as NGW-1. Common applications such as OpenCPN and Navionics have been tried and tested with our three gateways.