GPS vs GNSS in Surveying, Mapping, and Drone Applications
- Anvita Shrivastava
- 1 day ago
- 5 min read
The modern technologies of global navigation satellites have changed the approaches to positioning, surveying, mapping, GIS, and drone usage, as now it is possible to determine position precisely without using only traditional ground measurements. There are two names that are commonly mentioned in this industry: GPS and GNSS.
GPS stands for the Global Positioning System, which is the satellite navigation system provided by the USA. GNSS stands for the Global Navigation Satellite System, which is a more general term used for the set of satellite positioning systems including GPS, Galileo, GLONASS, and BeiDou.
It is important to distinguish GPS from GNSS when working with land surveying, UAV mapping, photogrammetry, GIS, LiDAR, construction, precision agriculture, etc.
What Is GPS?
GPS is a satellite navigation system that was created and is being maintained by the United States government. It includes several satellites that send time and location signals to GPS devices on Earth.
Using the time it takes for signals to reach the device, GPS calculates the user's position in terms of latitude, longitude, altitude, and accurate time.
The use of GPS is typical for:
Land surveys
Vehicle location
GIS data acquisition
Drone location
Construction staking
Asset mapping
Agriculture
Emergency management
Still, GPS is just one satellite navigation constellation, and it is important to remember this point when discussing modern positioning technologies.
What Is GNSS?
The acronym GNSS stands for Global Navigation Satellite System and denotes the entire set of satellite positioning systems. Modern GNSS receivers can work with signals of several different constellations as opposed to solely depending on GPS.
Major GNSS constellations are:
GPS - United States
GLONASS - Russia
Galileo - European Union
BeiDou - China
Additional satellite systems of various regions and augmentation systems may be supported by particular GNSS receivers as well.
Combining several constellations is likely to provide more visible satellites and enhance the satellite geometry and positioning performance in general.
GPS vs GNSS: Key Difference
The simplest way to understand the relationship is:
GPS is a GNSS system, but GNSS is not limited to GPS.
A GPS-only receiver primarily uses GPS satellites. A modern multi-constellation GNSS receiver can simultaneously process signals from GPS, Galileo, GLONASS, BeiDou, and potentially other supported systems.
Feature | GPS | GNSS |
Meaning | One satellite navigation system | General term for satellite navigation systems |
Main constellation | US GPS | GPS, Galileo, GLONASS, BeiDou, etc. |
Satellite availability | Limited to GPS | Multiple constellations |
Positioning reliability | Good | Generally higher with multi-constellation reception |
Surveying use | Common | Standard for high-accuracy applications |
Drone applications | Widely used | Increasingly common |
RTK support | Yes | Yes, depending on receiver and correction service |
Why GNSS Is Important in Surveying
Accuracy on the order of centimeters is required for modern surveying operations in applications like boundary surveys, construction layout, topography, and infrastructure development.
Modern GNSS receivers are capable of utilizing multiple satellite constellations and carrier-phase information to provide much better accuracy compared to traditional standalone navigation.
RTK GNSS
Real-Time Kinematic (RTK) positioning involves carrier-phase measurements and correction data from a base station or networks.
RTK positioning process usually involves the following steps:
Satellite systems send positioning signals.
The rover receiver receives satellite signals.
Base station or correction networks provide reference information.
Ambiguities in carrier phase measurements are resolved.
The receiver determines the corrected location, which may be accurate to centimeters under appropriate conditions.
Applications of RTK include:
Boundary surveys
Construction layout
Topography
Machine control
UAV ground control
Precision farming
PPK GNSS
The technique of Post-Processed Kinematic (PPK) involves the processing of the GNSS observation data obtained from a survey at a later stage.
PPK technology is especially beneficial in drone mapping since it allows recording GNSS data during the flight and later correction of its trajectory by means of reference data.
In contrast to RTK, PPK technology does not demand continuous correction throughout the course of the flight; however, it requires the GNSS observation data and reference information of high quality.
GNSS in Drone Mapping
GNSS has become an integral element of UAV photogrammetry.
A drone with a GNSS receiver can record the coordinates of the aircraft when acquiring aerial images. When integrated with RTK and PPK, the GNSS information can substantially enhance the georeferencing process of the aerial imagery.
Typical drone mapping workflow:
Mission planning → GNSS positioning → Image acquisition → RTK/PPK processing → Photogrammetry → Orthomosaic/DSM/DTM creation → Accuracy assessment
GPS vs GNSS for Drone Applications
While many consumer and commercial drones are called "GPS-positioning" ones, contemporary devices are able to track not one but several GNSS constellations.
Some of the benefits that a multi-GNSS system provides for drones for mapping are:
Greater Number of Satellites
The receiver that is able to observe several constellations has more satellites to observe than the receiver designed to track only the GPS constellation.
A greater number of satellite observations enhances accuracy and satellite geometry.
Greater Availability
Satellite signals may be partially blocked by buildings, terrain, trees, and other obstacles. Having the ability to track several constellations helps keep a sufficient number of usable satellites.
Enhanced Georeferencing
When GNSS positioning is used together with RTK and PPK, this technique will allow decreasing the necessity to use a great number of traditional ground control points.
Effective Mapping
The accurate positioning of the aircraft helps to integrate aerial photos into the photogrammetric processing pipeline more effectively.
GNSS vs GPS Accuracy
It is critical not to assume that GNSS will always be more accurate than GPS.
The accuracy of the positioning system depends on many parameters, such as:
Receiver's quality
Antenna type
Geometric configuration of the satellites
Frequency of signals
Correction type
Atmosphere condition
Multipath
Obstructions
Time of observation
Methodology of processing
A good GPS receiver will have better performance than a poor multi-constellation receiver.
That is why the number of satellite constellations is only one of the performance characteristics.
GPS and GNSS in GIS Mapping
GIS analysts rely on GNSS receivers to capture precise coordinates of field objects like:
Roads
Utility poles
Property borders
Pipeline networks
Structures
Drainage networks
Vegetation cover
Survey markers
Environmental sample collection points
The collected coordinates can subsequently be added to the GIS platform and saved in various formats, including GeoJSON, Shapefile, GeoPackage, GeoParquet, and checkpoints. GeoTIFF-based workflows.
It is worth considering that the choice of coordinate reference systems is essential. GNSS receivers tend to output geographic coordinates relative to a global reference frame, whereas GIS systems may utilize projective coordinate systems for a certain area.
GPS vs GNSS: Which Should You Use?
GPS might be good enough for basic navigation and positioning needs.
In professional work such as surveying, construction, mapping, LiDAR applications, and photogrammetry using drones, multi-constellation GNSS might be the right technology since today's receivers are capable of using observations from several satellite systems at once.
Nevertheless, the best option should be selected depending on various factors.
GPS and GNSS are closely connected but are not interchangeable terms. GPS is just one of the satellite navigation constellations, while GNSS includes a range of global satellite positioning systems.
Modern surveying, GIS, and UAV surveying technologies use multi-constellation GNSS receivers that give users the opportunity to work with data from different satellite constellations and use positioning methods like RTK and PPK.
In UAV photography, GNSS positioning may help to increase the quality of georeferencing and minimize control points in certain workflows. In land surveying and construction, RTK and other GNSS positioning methods allow collecting coordinates quickly and precisely.
Knowledge of the differences between GPS and GNSS can be useful for choosing appropriate positioning technology for developing surveying, GIS, mapping, LiDAR, and UAV workflows.
For more information or any GPS and GNSS questions, please don't hesitate to contact us at:
Email:
USA (HQ): (720) 702–4849
Comments