What is GNSS positioning? How is your position calculated? Explaining satellite-based positioning methods | NEXTY Electronics, a trading company for electronic components and semiconductors

What is GNSS positioning?

We use location information every day through smartphones, car navigation systems, etc., but do you know how location is calculated?
GNSS satellite positioning is used to calculate location, including on smartphones and car navigation systems.
In this column, we will introduce how to determine your location using GNSS satellites.
*For more information on GNSS satellites, please refer to the column "What is GNSS?"

What is GNSS?

Examples of connected devices for GNSS positioning - car navigation systems, smartphones

List of positioning methods using GNSS satellites

Positioning methods using GNSS satellites can be broadly divided into two types: "single-unit positioning" and "relative positioning."
Below is an overview of the most common positioning methods.
The next chapter will explain each positioning method in detail.
The key point is that you can use them depending on the required positioning accuracy.

Positioning method		overview	Position accuracy
Standalone positioning		A method of positioning using a single receiver *Used in car navigation systems, etc.	About 10m
Relative Positioning	Relative Positioning	A method of positioning using two or more receivers Errors can be reduced by determining the relative positional relationship See below for DGNSS positioning, RTK positioning, and network RTK positioning. Included in relative positioning	Approximately several meters
	DGNSS positioning	Combining one receiver with a known point (DGPS station) Positioning method The DGPS service using DGPS stations ended in 2019. Instead, it will continue to use correction information from geostationary satellites (MSAS in Japan).	Approximately several meters
	RTK positioning	Combining one receiver with a known point (reference station) Positioning method A reference station is required near the measurement point (if one does not exist, it must be installed).	A few centimeters
	network RTK positioning	Combining one receiver with multiple known points (electronic reference stations) Positioning method Receives location information from electronic reference stations established by the Geospatial Information Authority of Japan via the network and uses it as correction information	A few centimeters

What is standalone positioning?

Standalone positioning is, as the name suggests, a method of positioning using a single receiver with GNSS satellites.
This is the most familiar positioning method, used in car navigation systems, smartphones, etc.
The receiver acquires information from four or more satellites and calculates the position based on the acquired information.
The distance between the satellite and the receiver required for positioning is calculated based on the difference between the time the radio waves are sent and received.

What is relative positioning?

Relative positioning differs from single-unit positioning in that it uses two or more receivers to perform GNSS satellite positioning and handles relative position differences.
In relative positioning, just like single-unit positioning, the receiver calculates its position based on information from four or more satellites.
By treating positioning information relative to one another, inherent errors can be offset, improving accuracy.

What is DGNSS (Differential GNSS) positioning?

DGNSS positioning is different from standalone positioning in that it is a method of positioning that combines one receiver with a known point (DGPS station).
Position correction is performed based on correction information from DGPS stations, which are known points.
Originally, correction signals from DGPS stations on the ground were used, but with the cessation of DGPS station operations, correction information from geostationary satellites is now used instead.

What is RTK (Real-time kinematic) positioning?

RTK is a method of high-precision positioning based on correction information from reference stations installed on the ground.
The difference with DGNSS positioning is that the receiver's satellite positioning uses carrier wave phase (described below) instead of standalone positioning, which is expected to improve positioning accuracy.
Because it is necessary to receive correction information from a reference station, depending on the positioning environment, such as when signals from an existing reference station cannot be received, it may be necessary to install a reference station near the receiver.

What is network RTK positioning?

Network RTK positioning is a method of exchanging data between a reference station and a receiver via a server.
The receiver's positioning data is sent to the reference station, and correction information for the positioning data is sent from the reference station to the receiver.
Achieves high-precision positioning.
Unlike RTK, one of the advantages is that correction signals can be received through a server, eliminating the need to install a reference station.

What is carrier phase?

Carrier phasing is a method of improving positioning accuracy by improving the accuracy of the distance between the satellite and the receiver.
The distance between the satellite and the receiver required for positioning is measured as "number of wavelengths (N) + less than 1 wavelength."
Of these, the carrier wave phase refers to the part less than one wavelength, and by calculating the difference in distance from multiple satellites, it is possible to improve positioning accuracy.