Difference Between GPS and DGPS: Accuracy and When to Use

What is the difference between GPS and DGPS?

A GPS receiver takes its position from the satellites with nothing to check it against, so a few metres of error is normal. DGPS, the differential global positioning system, parks a reference station receiver over a point of known position, learns the error there and passes the fix to the measuring receiver. Survey-grade work then comes within a centimetre or two, using the same satellites and GPS signals.

The gap matters because a plot boundary, culvert level or pipeline crossing cannot be built to "somewhere within four metres". A phone finds a site but cannot fix where a wall should stand.

Strictly, GPS is the United States global positioning system. Receivers today also track GLONASS, Galileo, BeiDou and India's NavIC, together called GNSS, as our Mezux guide: GNSS Explained for Surveyors describes. On Indian sites, "GPS" still means a standalone receiver and "DGPS" a corrected one, and this article follows that usage.

GPS vs DGPS at a glance

For a rough idea of plot size from a phone or a map, check the area on a map first. When the answer has to hold up, book a corrected survey.

Where does ordinary GPS error come from?

Error comes from satellite clocks and orbits, from signal delay in the ionosphere and lower atmosphere, from reflections off buildings, and from the receiver itself. US government performance pages put the worst-case signal-in-space range error within 7.8 m at 95% confidence. A good single-frequency receiver manages roughly 2.2 m horizontally 95% of the time¹, and Indian towns are often worse.

• Clock, orbit and atmosphere: broadcast timing errors plus ionospheric delay, the largest natural error, and tropospheric delay from humidity.
• Multipath: signals bouncing off walls, water tanks and vehicles.
• Poor geometry: satellites bunched in one part of the sky magnify small errors.

How does a differential correction remove that error?

The base station, set on surveyed coordinates, compares the satellite position with the true one and sends the gap to the rover, which subtracts it. Both receivers see the same satellites through nearly the same air, so most error cancels. That is how DGPS works.

The correction can travel live by radio or mobile data, or both receivers' raw data can be processed together later. Live work suits plot corners and stake-out, while static sessions suit main control. The field method and deliverables are on our service page if you want to learn about DGPS survey as a booked job.

Real-time or post-processed?

Both routes are differential and differ only in when the arithmetic happens. Real time gives a corrected coordinate in seconds for hunting a buried pillar. Post-processing logs raw files and combines them afterwards, so a dropped radio link loses nothing. Large jobs use static sessions for main control and real time for the detail.

Cancellation weakens with distance, so surveyors keep the GPS receiver on the rover close to its base for accurate satellite based positioning, or switch to a network of reference stations.

DGPS, RTK and CORS: how do they relate?

Classic DGPS corrects the coarse code and gives sub-metre results, while RTK uses the finer carrier phase and gives centimetres. CORS is a network of permanent stations that can supply either. A quoted "DGPS survey" in India is normally run in RTK or static carrier-phase mode, which is why centimetres are promised.

Survey of India runs a national CORS network of ground based reference stations. Its note describes real-time network RTK at ±3 cm, stations typically 60–70 km apart, round-the-clock RTCM corrections, and daily to yearly subscriptions, so a user needs only a rover². A network rover depends on mobile data, so remote routes still use a private base and radio. For the layout and access, see: CORS Network in India.

Coordinates come out on WGS 84 and are normally converted to UTM for drawing. The mainland spans zones 42N to 47N, with Delhi NCR in 43N, and a drawing that mixes zones or grids often explains a "wrong survey" complaint.

Which one should you use for your job?

Use plain GPS to find and roughly measure a site, and DGPS whenever a position or level will be built on, registered, paid for or argued over.

• Rough field size before a visit: phone GPS is enough.
• Plot corners before a sale or bank loan: DGPS, with a drawing and coordinate list.
• Drone or topographic ground control, and long alignments: DGPS in static or RTK mode along the route.
• Dense trees or tall buildings: DGPS control in the open, then a total station under cover.

Which GPS and DGPS beliefs cause trouble on site?

Five beliefs about standalone GPS, DGPS and RTK keep causing trouble on site.

• "My phone says 3 m, so the point is within 3 m": the figure is an optimistic estimate at a lower confidence than surveyors use.
• "More satellites means survey accuracy": without a correction, shared atmospheric error stays.
• "DGPS heights are sea-level levels": they sit above the ellipsoid and need a geoid model or benchmark tie.
• "A fixed solution is always right": heavy multipath can give a fix wrong by decimetres, caught by a check shot.
• "Corrected coordinates suit any drawing": only if datum and projection match.

What does a DGPS survey cost with Mezux Touch?

A plot up to 1 acre starts from ₹12,000, and plots of 1–5 acres are ₹2,500 per acre with a ₹12,000 minimum. Control points along a route are ₹3,000 each, GST extra, and you pay the amount set down in our written quotation.

Four base-and-rover sets belong to the company. For Delhi NCR the crew arrives on the booking day or within 1 working day. Other states are handled by the team member who lives there, starting at once or one working day later at most. Mobilisation or travel, where applicable, is a separate quoted line. About three working days after fieldwork you receive Excel or CSV coordinates, a DWG and PDF drawing and, where useful, a KMZ. Unsure whether you need the corrected version? Tell us the job and get expert advice on your site for your project; sometimes the honest reply is that a phone is enough.

Sources

1. GPS.gov (US government), “GPS Accuracy”, performance page. gps.gov
2. Survey of India, “Note on RTK and CORS”. surveyofindia.gov.in

Frequently asked questions

Does DGPS beat GPS on accuracy?

Yes, by a wide margin. On its own a receiver strays by a few metres, whereas a survey-grade differential pair holds about 1–2 cm horizontally and 2–3 cm vertically.

Is RTK the same as DGPS?

RTK is the carrier-phase form of differential positioning and gives centimetre results; classic code DGPS gives sub-metre results. For the method in detail, read more on RTK (Real Time Kinematic) Survey.

Can DGPS cope under tree cover or among tall buildings?

Poorly, because signals are blocked or reflected and fixes take longer or go wrong. Surveyors fix control in the open and finish covered areas with a total station.

Can a mobile phone become a DGPS?

Some phones accept corrections and improve to around a metre in good conditions, but they are not survey instruments and do not give reliable levels.

What is a safe distance between rover and base?

Accuracy slowly worsens with distance; surveyors keep the rover within a few kilometres of its base for detail work, or use a network of reference stations.

What is differential GPS accuracy for height?

About 2–3 cm vertically on survey-grade equipment, roughly half as good as horizontal, because satellite geometry is weaker in the vertical.

Written by Saniya Parveen · Technically reviewed by Rahul Rai · Updated 8 November 2026