Modern surveying relies heavily on precise positioning. If it’s a building project, land survey, mining operation, highway development, GIS mapping, or infrastructure project, accurate information about location is crucial for making informed decisions. Satellite-based technologies like GNSS and DGPS have made surveying more efficient and more accurate than many conventional methods.
Yet, GNSS and DGPS are typically viewed as the same technology, although they have distinct meanings and uses. GNSS (Global Navigation Satellite System) is a broad term used to describe satellite positioning systems that utilize constellations like GPS, GLONASS, Galileo, and BeiDou. DGPS (Differential Global Positioning System) is a correction process that enhances GPS positioning using information from a recognized reference station.
So, GNSS vs DGPS: which is the better surveying technology? The answer is contingent on the accuracy requirements, project work environment, correction technique, equipment, and budget. Let’s examine the major distinctions and decide which method is the best in the current world of surveying.
What Is GNSS?
GNSS is the abbreviation for Global Navigation Satellite System and refers to satellite-based positioning technology.
Modern GNSS receivers are able to receive signals from several satellite constellations, such as:
- GPS – United States
- GLONASS – Russia
- Galileo – European Union
- BeiDou – China
Utilizing signals from different constellations can increase the availability of satellites and the reliability of positioning. Professional GNSS receivers are also able to accommodate multiple frequencies and correction services, such as RTK.
GNSS surveying is extensively employed for land surveys, topographic mapping, construction, mining, roads, agriculture, GIS, and infrastructure development.
What Is DGPS?
DGPS is short for Differential Global Positioning System. This is a method to increase the accuracy of GPS positioning.
In a typical DGPS configuration, a reference station is set up at a predetermined site. It receives signals from satellites, analyzes position errors, and then sends correction data to the receiver of a rover. The rover uses these corrections to improve its location.
The most basic procedure is:
Satellite signals → Reference Station → Correction Information → Rover → Improved Position
DGPS is often used to perform GIS mapping, asset mapping, field data collection, utility surveys, And other applications that require better positioning than standalone GPS.
GNSS vs DGPS: Key Difference
The easiest way to comprehend the difference is:
GNSS is a satellite positioning system, and DGPS provides a means for increasing GPS positioning accuracy.
GNSS can be used in conjunction with correction technologies like RTK. DGPS specifically utilizes data for differential correction.
So, they aren’t always directly competing. A professional GNSS receiver could actually utilize differential and RTK correction data in order to offer extremely precise positioning.
GNSS vs DGPS Accuracy
Accuracy is among the most important aspects in surveying.
A standard standalone GNSS receiver could offer metre-level positioning, based on the device and the conditions. Professional multi-frequency GNSS receivers that make use of RTK corrections are able to achieve centimetre-level accuracy in the right conditions.
DGPS increases the accuracy of traditional GPS by using differential corrections. However, its accuracy is dependent on the receiver, reference station, correction source, distance between the rover’s location and the reference station, satellite visibility, and environmental conditions.
Accuracy is also affected by:
- Amount of visible satellites
- Satellite geometry
- Surface conditions
- Multipath interference
- Trees and buildings
- Quality of the antenna and receiver
- Correction-data quality
For precision construction and engineering surveys, RTK GNSS is generally preferable.
GNSS vs DGPS Comparison
| Feature | GNSS | DGPS |
| Full Form | Global Navigation Satellite System | Differential Global Positioning System |
| Basic Purpose | Satellite-based positioning | Improved GPS positioning |
| Satellite Support | Multiple constellations | Primarily GPS-based |
| Accuracy | Can reach centimetre-level accuracy using RTK | Better than standalone GPS |
| RTK Support | Common in professional-grade receivers | Different from traditional RTK |
| Main Uses | Construction, surveying, and mapping | GIS, mapping, and field data collection |
| Flexibility | High | Application-specific |
Is Better for Land Surveying?
To conduct professional land surveys, using a modern multi-frequency GNSS receiver with RTK capabilities is usually the most versatile choice.
GNSS equipment is able to track several satellite constellations and receive correction data that provides highly precise coordinates. It is particularly helpful for:
- Boundary surveys
- Topographic surveys
- Construction layout
- Highway and road surveys
- Control point establishment
- Utility mapping
- Land development
The main benefit of GNSS technology is that it doesn’t require a direct line of sight between each measured point. This makes it more efficient for areas with large open spaces.
But GNSS may not perform effectively when satellite signals are inaccessible due to dense trees, tall buildings, tunnels, or underground areas. In such cases, surveyors can combine GNSS with a total station or other surveying equipment.
Advantages of GNSS Surveying
1. Multiple Satellite Constellations
Modern GNSS receivers are able to track several satellite systems, which means they have greater satellite availability and flexibility in positioning.
2. High Productivity
GNSS can assist surveyors in collecting coordinates in a short time over vast areas without needing an exact line of sight between each point.
3. RTK Capability
Professional RTK GNSS receivers can provide centimetre-level precision in the field under suitable conditions.
4. Wide Range of Applications
GNSS can be used for land surveying, construction, mapping, mining, roads, agriculture, and infrastructure development.
5. Advanced Features
Modern receivers are equipped with features like multi-frequency tracking, IMU tilt compensation, wireless connectivity, and integrated surveying software.
Advantages of DGPS
DGPS can be useful in various applications.
Improved positioning: Differential corrections can increase accuracy compared with standalone GPS.
GIS and mapping: DGPS can be helpful in collecting geographic data and mapping assets.
Field data collection: It can assist in determining the position of roads, utilities, infrastructure, and other field features.
Practical solution: For applications that don’t require centimetre-level RTK precision, DGPS can provide an efficient positioning solution.
GNSS vs DGPS vs RTK
These three terms can be difficult to understand, which is why it’s essential to be aware of:
- GNSS: Satellite-based positioning using one or more satellite constellations.
- DGPS: Differential correction technique employed to enhance GPS positioning.
- RTK GNSS: High-precision GNSS positioning using carrier-phase correction data.
For engineering and surveying applications that require high precision, RTK GNSS is often the preferred choice.
How to Choose the Right Surveying Equipment
Before buying a GNSS receiver or DGPS equipment, think about the following aspects:
Required Accuracy
Consider whether your project requires decimetre-level, metre-level, or centimetre-level positioning.
Satellite Support
For professional surveys, look for receivers that can work with multiple constellations and frequencies.
Correction Options
Make sure that the device is compatible with network RTK, UHF radio, cellular corrections, and base-rover configurations.
Field Software
Surveying software should support functions like stakeout, mapping, coordinate management, data export, and field calculations.
Durability and Battery
For harsh field conditions, tough construction and long-lasting batteries are essential.
Technical Support
Training, calibration, software support, replacement parts, and after-sales service are crucial for long-term equipment efficiency.
Applications of GNSS and DGPS
Both of these technologies are utilized in various industries.
Construction
Site positioning, measurement, grading, and positioning.
Highway and Road Construction
Topographic surveying, alignment, control points, and construction layout.
GIS and Mapping
Collection of geographical data and asset mapping.
Mining
Mine surveys, stockpile measurements, and machine positioning.
Agriculture
Field mapping, machine guidance, and precision agriculture.
Land Development
Boundary surveys, topographic surveys, and site planning.
Frequently Asked Questions
1. What’s the distinction between GNSS and DGPS?
GNSS is a broad satellite-based positioning technology that can use various satellite constellations. DGPS refers to a correction method that enhances GPS positioning by using data from an existing reference station.
2. Is GNSS more precise than DGPS?
GNSS and DGPS aren’t directly comparable since one is the satellite positioning system, while the other is a correction approach. A high-end RTK GNSS receiver has the ability to achieve centimetre-level accuracy under suitable conditions.
3. Which one is more suitable for land surveying: GNSS or DGPS?
For professional land surveying, a multi-frequency RTK GNSS receiver is typically more adaptable because it is able to support various satellite constellations And high-precision positioning.
4. Could GNSS be used to conduct RTK surveying?
Yes. Professional GNSS receivers are able to use RTK correction information to achieve centimetre-level positioning accuracy when satellite visibility and suitable correction services are available.
5. What exactly is the purpose of a GNSS receiver?
A GNSS receiver is used to calculate geographical positions in applications like land surveying, construction, GIS mapping, mining, roads, agriculture, and infrastructure development.
6. Are DGPS systems still in use today?
Yes. DGPS can be beneficial for GIS mapping, asset collection, environmental surveys, and other situations where enhanced positioning is required but the high precision of RTK is not necessary.
Conclusion:
The contrast between GNSS and DGPS isn’t just about deciding between one type of technology and another. GNSS is a broad satellite positioning technology, while DGPS is a differential correction technique designed to enhance GPS positioning.
For simple mapping and field-based data gathering, DGPS can be an efficient solution. For professional land surveying, construction, infrastructure, and engineering projects, a multi-frequency RTK GNSS receiver typically offers greater flexibility, efficiency, and accuracy.