What Is DGPS? Differential GPS Explained Simply (2026)
DGPS (Differential GPS) improves standard GPS accuracy from 5–15 metres down to 0.5–3 metres by applying real-time corrections from a reference station at a known location. The reference station measures the GPS error at its fixed position and broadcasts that error correction to nearby receivers. DGPS is widely used in marine navigation, GIS data collection, and asset tracking where sub-metre accuracy is needed but centimetre precision is not required. For survey applications requiring centimetre accuracy — construction stakeout, cadastral boundary, and precision infrastructure — RTK (Real-Time Kinematic) is the correct technology. DGPS and RTK are both differential positioning methods; RTK simply resolves the carrier-phase ambiguity that DGPS does not.
In This Guide
1. What Is DGPS?
DGPS stands for Differential GPS. It is a positioning technique that uses a second, stationary GPS receiver — called a reference station or base station — to measure and correct GPS errors in real time.
The Core Problem It Solves
Standard GPS receivers calculate position by measuring the time signals take to travel from satellites to the receiver. Errors creep in from several sources: atmospheric delays as signals pass through the ionosphere and troposphere, small inaccuracies in satellite orbits and clocks, and multipath reflections off nearby surfaces. These errors are largely correlated in space — two receivers close to each other experience almost identical errors at the same moment.
The DGPS Solution
A reference station placed at a precisely known location continuously measures these errors. It knows exactly where it should be. By comparing where GPS says it is to where it actually is, it calculates the error in real time. That error correction is then broadcast to nearby receivers — the GPS rovers. When a rover applies the correction, most of the shared error cancels out, and accuracy improves from 5–15 metres to 0.5–3 metres.
Note: "DGPS" technically refers to GPS-only differential correction. The modern equivalent covering all constellations (GPS, GLONASS, BeiDou, Galileo) is called DGNSS. In practice, the terms are used interchangeably in the industry.
2. How DGPS Works
DGPS Correction Process — 4 Steps
Reference Station Measures GPS Error
A reference station receiver is placed at a surveyed control monument whose coordinates are precisely known. It continuously tracks GPS satellites and compares the position it calculates from GPS signals to its true known position. The difference is the GPS error at that location and moment.
Error Correction Is Calculated and Encoded
The reference station calculates pseudorange corrections for each GPS satellite it can see. These corrections account for atmospheric delays, satellite clock errors, and orbit errors as they exist at that moment. The corrections are formatted as RTCM messages — the standard data format for differential corrections.
Corrections Are Broadcast to Rovers
The reference station transmits its corrections in real time. Broadcast methods include: UHF radio (short to medium range, up to 100+ km for high-power stations), internet via NTRIP (CORS network delivery), satellite broadcast (SBAS systems like WAAS in North America, EGNOS in Europe, MSAS in Japan), and dedicated marine radio beacons (used by coast guard networks for maritime DGPS).
Rover Applies Corrections and Improves Position
The rover receiver receives the corrections and applies them to its own GPS observations. The shared atmospheric and satellite errors cancel out, leaving a significantly more accurate position. The closer the rover is to the reference station, the more similar their errors are, and the more effectively the correction improves accuracy.
3. DGPS vs Standard GPS: Accuracy Comparison
DGPS closes the accuracy gap between consumer GPS and professional survey-grade equipment. The table below shows the key performance differences.
| Parameter | Standard GPS | DGPS |
|---|---|---|
| Horizontal accuracy | 5–15 metres | 0.5–3 metres |
| Vertical accuracy | 10–20 metres | 1–5 metres |
| Requires reference station | No | Yes |
| Requires data link | No | Yes (radio, internet, or satellite) |
| Real-time correction | No | Yes |
| Works offline | Yes | Reference station required |
| Typical applications | Navigation, tracking, mapping | GIS, marine, asset survey |
| Cost | Low (single receiver) | Medium (receiver + correction source) |
For most navigation, fleet tracking, and coarse GIS work, DGPS accuracy is sufficient. For applications requiring better than 0.5 metres — engineering survey, cadastral boundary, construction stakeout — RTK provides the required centimetre-level accuracy that DGPS cannot achieve.
4. DGPS vs RTK: When to Use Which
DGPS and RTK are both differential positioning techniques — both use a reference station to correct GPS errors. The fundamental difference is in which part of the GPS signal they use for positioning.
DGPS uses pseudorange measurements — the code-based timing signal. Pseudorange measurements have an inherent noise floor of about 0.3–1 metre, which limits DGPS accuracy to that same range regardless of how good the corrections are.
RTK uses carrier-phase measurements — the actual wavelength of the GPS signal (approximately 19 cm for L1). By resolving the integer number of wavelengths between satellite and receiver (called integer ambiguity resolution), RTK achieves millimetre-level measurement noise. Combined with differential corrections, this delivers ±8–15 mm horizontal accuracy in Fixed solution.
When DGPS Is Sufficient
- Marine navigation and harbour manoeuvring
- GIS data collection for utility asset mapping
- Fleet tracking and vehicle positioning
- Aerial photography ground control (where ±1 metre is acceptable)
- Environmental boundary surveys (wetland mapping, shoreline tracking)
- Agriculture guidance systems (row guidance, not precision stakeout)
When RTK Is Required
- Construction stakeout (column positions, road alignment, drainage)
- Cadastral and property boundary survey
- Engineering control and as-built documentation
- Precision agriculture pile and foundation stakeout
- Any application where tolerance is tighter than 0.3 metres
APEKS receivers support both modes: DGPS/DGNSS mode for sub-metre applications and full RTK Fixed mode for centimetre-level survey work — on the same hardware.
5. Types of DGPS Systems
Not all DGPS correction sources are the same. The main types:
1. Local DGPS / Local Base Station
A user-deployed reference station transmits corrections directly to nearby rovers via UHF radio. Range: typically 10–50 km. Accuracy: best available (short baseline, fresh corrections). Used in: remote surveying, construction, mining, precision agriculture.
2. CORS Network / NTRIP
A national or commercial network of permanently installed reference stations delivers corrections via the internet (NTRIP protocol). Coverage: national or regional. Accuracy: 0.1–1 metre for DGPS, ±8 mm for RTK. Examples: InaCORS (Indonesia), IBGE-RBMC (Brazil), TrigNet (South Africa).
3. SBAS (Satellite-Based Augmentation System)
Geostationary satellites broadcast corrections covering continental areas. No receiver subscription needed. Systems: WAAS (North America), EGNOS (Europe), MSAS (Japan), GAGAN (India), SDCM (Russia). Accuracy: typically 1–3 metres. No subscription required — corrections received directly via satellite. Latency is higher than local DGPS.
4. Maritime DGPS Beacons
Coast guard stations in many countries broadcast DGPS corrections on 283.5–325 kHz radio frequencies for free marine use. Range: 200–300 km. Accuracy: 1–5 metres. Widely used in commercial shipping and coastal survey.
6. DGPS Applications
DGPS is the appropriate technology choice for applications where sub-metre accuracy is needed but centimetre precision is not justified by the application or budget.
Marine Navigation
Harbour approach, vessel docking, dredge positioning, and coastal survey all benefit from DGPS. The 0.5–3 m accuracy window is adequate for safe navigation in most maritime contexts.
GIS and Asset Mapping
Utility companies mapping underground cables, pipes, and poles across large areas use DGPS/DGNSS for efficient data collection where position tolerance of 0.5–2 m is acceptable.
Fleet and Logistics Tracking
Construction site vehicle tracking, port container management, and agricultural machine guidance use DGPS for cost-effective sub-metre positioning without the infrastructure overhead of RTK.
Environmental Monitoring
Shoreline change mapping, flood boundary delineation, and forestry survey use DGNSS for rapid, sub-metre data capture across large areas.
Note on Modern Receivers
Most modern professional GNSS receivers — including all APEKS models — support both DGPS and RTK modes on the same hardware. You do not need separate equipment for DGPS and RTK applications.
7. Limitations of DGPS
Cause: DGPS is fundamentally limited by pseudorange measurement noise. Even with perfect corrections, the noise floor of code-based ranging prevents sub-decimetre accuracy.
Fix: For applications requiring better than 0.3 m — construction stakeout, cadastral survey, engineering control — upgrade to RTK mode. Modern APEKS receivers support RTK on the same hardware; no equipment change required, only a correction source capable of delivering carrier-phase corrections (RTCM 3.x from a CORS network or local base).
Cause: Atmospheric conditions differ between the reference station and rover at longer distances. The corrections broadcast by the reference station become less representative of conditions at the rover location as baseline increases.
Fix: Use a reference station within 20–30 km for best DGPS accuracy. SBAS corrections (WAAS, EGNOS) provide a continental average that may be less accurate than a nearby local station but require no infrastructure.
Cause: DGPS corrections are valid for a limited time. Atmospheric conditions change, and a correction computed 10 seconds ago may not reflect current conditions accurately. High latency in the correction delivery (slow radio link, overloaded NTRIP caster) makes corrections stale.
Fix: Use a correction source with low latency — local UHF radio base provides fresh corrections every second. For NTRIP delivery, confirm differential age is below 3–5 seconds at the rover. Maritime DGPS beacons may have higher latency (5–10 seconds) — adequate for vessel navigation but not for dynamic positioning applications.
8. FAQ
Is DGPS the same as GPS?
No. Standard GPS is a single receiver calculating position from satellite signals alone, with accuracy of 5–15 metres. DGPS adds a reference station that measures GPS errors at a known location and broadcasts corrections to nearby rovers, improving accuracy to 0.5–3 metres. DGPS requires two receivers and a correction data link; standard GPS requires only a single receiver.
What is the difference between DGPS and RTK?
Both are differential positioning methods using a reference station. DGPS uses code-based pseudorange measurements, limiting accuracy to 0.5–3 metres. RTK uses carrier-phase measurements and resolves integer ambiguities, achieving ±8–15 mm accuracy in Fixed solution. RTK requires more processing and a higher-quality correction signal (carrier-phase RTCM 3.x), but delivers orders of magnitude better accuracy for survey applications.
Do I need special equipment for DGPS?
Any GNSS receiver that supports differential correction input can use DGPS. Most professional survey receivers — including all APEKS models — support both DGPS and RTK modes on the same hardware. For SBAS DGPS (WAAS/EGNOS), no additional infrastructure is needed — corrections arrive via satellite directly. For local base or CORS DGPS, you need a correction source and a data link (radio or internet).
Can DGPS work without the internet?
Yes. DGPS corrections can be delivered via UHF radio from a local base station, via satellite (SBAS systems like WAAS or EGNOS), or via dedicated maritime radio beacons — none of these require internet. NTRIP delivery via internet is one option, not the only option. For remote areas without internet, a local UHF base station or SBAS provides DGPS corrections without any connectivity requirement.
What accuracy can I expect from DGPS in practice?
With a local CORS or base station within 20 km, expect 0.3–1 metre horizontal accuracy under open sky. SBAS systems (WAAS, EGNOS) typically deliver 1–3 metres. Maritime DGPS beacons deliver 1–5 metres at coastal ranges. Accuracy degrades with baseline distance and is affected by sky obstruction, atmospheric activity, and correction latency. For better than 0.3 metres, RTK is required.
DGPS MODE AND RTK MODE. ONE RECEIVER.
APEKS receivers support both DGPS/DGNSS sub-metre mode and full RTK Fixed mode at ±8 mm — on the same 1408-channel hardware. Start with DGPS for GIS and asset mapping. Switch to RTK for construction and survey. No equipment change.
View APEKS GNSS Receivers →References and Further Reading
- RTCM Standard 10403.3 — Differential GNSS Services
- ISO 17123-8:2015 — Field Procedures for GNSS RTK
- FAA WAAS Performance Standard, 2020
- EGNOS Service Definition Document, EUSPA 2023
- APEKS APS1 Handheld RTK Datasheet, 2026
- ApekSurv Field Software User Guide, 2026