GNSS Meaning in Surveying: Satellites and Receivers

What is the meaning of GNSS in surveying?

GNSS is the collective name for satellite-based positioning and navigation systems. A survey-grade GNSS receiver tracks signals from several constellations on more than one frequency and measures both the code and the carrier phase. On its own it fixes a position to a few metres; combined with corrections from a base station or network it reaches centimetres.

Which systems can be used over India?

GNSS control often comes before a scan for buried services on the same route; if so, calculate the survey cost for that part online.

India also runs GAGAN, a satellite-based augmentation system that improves the Global Positioning System for aviation. It helps navigation but is not a substitute for survey corrections.

How accurate is each way of using GNSS?

The method, not the satellites, decides the answer. A handheld or phone working alone on code measurements gives a few metres. Augmentation brings that nearer a metre. A GNSS survey with base-and-rover or network corrections, using the carrier phase, reaches 1–2 cm horizontally. That last step, which is how survey-grade DGPS works, turns a navigation fix into a boundary or design coordinate.

What limits a GNSS survey?

Mostly the sky view and the atmosphere, not the receiver. Understanding the meaning of GNSS in surveying is largely understanding these limits:

• Ionosphere: delays GPS signals and those of other systems by an amount that depends on frequency, which is why dual-frequency receivers can remove most of it.
• Troposphere: water vapour and air pressure add delay, larger at low elevation angles.
• Multipath: signals bouncing off walls, vehicles or water arrive late and bias the result.
• Satellite geometry: a high PDOP, satellites bunched in one part of the sky, weakens the fix.
• Obstruction: canopy and tall buildings cut satellites out altogether.

More constellations ease the last two problems: in a narrow lane a GPS-only receiver may see too few satellites, while a multi-system receiver often sees enough to fix.

A field example beside a glass building

Multipath shows up as points that will not sit still. A rover set up two metres from a glass-fronted office block in an industrial sector may report a fixed solution. Yet repeated occupations a minute apart scatter by three to five centimetres. Moved ten metres into open ground, the same receiver repeats within a centimetre. The building has not blocked the satellites; it has reflected them. Our crews therefore fix control away from façades, sheds and parked lorries. They carry positions into tight spots optically instead of accepting a fix that looks good on the screen but fails a repeat.

Mistakes people make with GNSS coordinates

Most are about labels and settings, not satellites.

• Recording a navigation fix from a phone as if it were a survey point.
• Leaving the antenna height at zero, so every level is off by the pole length.
• Storing points in latitude and longitude on one job and UTM on the next, without saying which.
• Setting too low an elevation mask, which lets noisy satellites near the horizon into the solution.

What travels with GNSS data in a Mezux deliverable

Coordinates never leave our office without their metadata. Each control report lists the constellations tracked, the method (RTK, network RTK or static), and the reference frame and zone. It also gives the geoid model used for heights and the residuals on check points. Field receivers output positions in the common NMEA 0183 format for logging and take corrections as RTCM messages, while ISO 17123-8 gives a field procedure for testing RTK equipment. India's own system, NavIC, is operated by ISRO; whether a receiver tracks it depends on the hardware.

Static or real time: which GNSS method when?

Real-time methods suit detail and stake-out; static sessions suit control that everything else will hang from. In a static survey two or more receivers record simultaneously for half an hour to several hours, and the data are processed afterwards, often against data from a reference station. The long sessions average out multipath and atmospheric effects, so static points make the backbone for a corridor or a large layout. Real-time work then fills in the hundreds of detail points between them in a fraction of the time. A typical Mezux route job uses both: a handful of static control pillars, then RTK or network RTK for everything else.

How GNSS fits with other survey methods

GNSS gives coordinates quickly in the open; optical instruments finish the job where the sky is blocked. We place GNSS control in open spots and carry it into courtyards, basements and dense lanes by total station, using the method in Total Station Traverse explained. Heights from GNSS are ellipsoidal, so levels for drains and plinths are checked against a benchmark; see the Mezux guide: Survey Benchmark (BM). The decision is set out in when you need a total station survey.

For control on your own site, ask for a quotation for your project.

Frequently asked questions

Is GNSS more accurate than GPS?

The physics is the same, but a receiver using several constellations sees more satellites than a GPS receiver alone. Better geometry then means faster, more reliable fixes.

Can a mobile phone do a GNSS survey?

A phone gives a few metres at best. Boundary and design work needs a survey receiver with corrections.

How do I book a GNSS or DGPS survey?

Share your location and the purpose of the DGPS (differential global positioning system) work; see booking a DGPS survey for what we need.

Does NavIC make a survey more accurate?

It adds satellites over India, which can help geometry in obstructed places. Centimetre accuracy still depends on carrier-phase corrections from a base or a network of ground-based reference stations.

What is an elevation mask?

A cut-off angle below which satellites are ignored. Signals close to the horizon pass through more atmosphere and suffer more multipath, so they are excluded.

Can GNSS work indoors or in basements?

No. Survey receivers need a direct view of the sky. Inside buildings, positions are carried in from outside by total station.

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