GPR Glossary: Radar, GNSS and Utility Survey Terms

What does this GPR glossary cover?

It defines the words that appear in GPR reports, land survey drawings, revenue papers and utility coordination meetings in India, from A-scan to WGS84. Twenty-five terms have their own page with a worked example; the rest are defined in a line or two below, grouped by subject so related words sit together.

Clients often meet these words for the first time in a quotation or a drawing legend. A site engineer may know a killa but not a hyperbola; a GIS team may know a shapefile but not a khewat. The aim is plain definitions that are technically right, with the state named wherever land-record terms differ from one state to another.

A–Z index of term pages

Each link below opens a full page on that term.

A — A-scan · Active vs passive locating · As-built drawing

B — B-scan · Benchmark (BM)

C — C-scan and depth slice · CORS network in India

D — Depth of penetration · Dielectric constant

E — Easting and northing

G — GNSS · GPR hyperbola

J — Jamabandi

K — Khasra and killa numbers

M — Migration

R — RTK survey

S — Shapefile vs KMZ · Sonde

T — Tolerance zone · Total station traverse · Two-way travel time

U — Utility conflict matrix · UTM zones of India

V — Vacuum excavation

W — WGS84 datum

GPR and radar terms

These describe how ground penetrating radar (GPR) records, displays and processes its data. GPR is a geophysical survey method that sends electromagnetic waves into the ground and builds images from the echoes. Most confusion about depth comes from three of them, travel time, velocity and permittivity, so start there if a report's depth figures puzzle you.

• A-scan: one recorded trace of amplitude against time at a single antenna position (see: A-Scan in GPR).
• Antenna frequency: the centre frequency of a radar antenna, from about 100 MHz to 2.6 GHz in common use. Lower bands reach deeper; high frequency bands resolve smaller, shallower objects.
• Attenuation: the loss of radar energy as it travels, driven mainly by electrical conductivity. Wet clay and salty ground lose signal fastest.
• B-scan: the vertical image built from traces recorded along a line, with distance across and time or depth down.
• Background removal: a filter that subtracts the average trace from a section to suppress flat ringing; used carelessly it also deletes real horizontal layers.
• C-scan / depth slice: a plan-view map of reflection strength at one depth, cut from a grid of closely spaced lines.
• Common midpoint (CMP): a velocity test in which the two antennas are moved apart symmetrically about one point; the change in arrival time gives the ground velocity.
• Dewow: a filter that strips the slow, low-frequency drift from the start of each trace before other processing.
• Dielectric constant: relative permittivity of the ground, the property that sets radar speed; see: Dielectric Constant (Relative Permittivity) in GPR.
• Depth of penetration: how deep usable echoes still come from, controlled by frequency, soil conductivity and target size.
• Gain: amplification that increases with recording time so a faint deep return signal can be seen; too much of it turns noise into false targets.
• Hyperbola: the arch a pipe, cable, stone or other buried object draws on a section when the line crosses it, with the object at the apex.
• Migration: processing that collapses arches to points and restores sloping layers to their true angle, using the measured velocity.
• Polarity: whether a reflection starts with a positive or negative swing. Metal and water-filled pipes show one polarity, air-filled ducts and voids the other.
• Radargram: any displayed radar image; in everyday use, a B-scan.
• Resolution: the smallest gap at which two objects appear separate. Vertically it is roughly a quarter of the wavelength, so higher frequencies see finer detail.
• Ringing: repeated echoes that continue below a reflector, typical under metal or when the antenna is poorly coupled to the ground.
• Time window: how many nanoseconds the receiving antenna listens after each pulse; together with velocity it sets the deepest point displayed.
• Time zero: the instant on each trace that corresponds to the ground surface, aligned during processing.
• Two-way travel time: the round-trip time of a pulse to a reflector and back, the quantity radar measures; our Two-Way Travel Time (GPR) guide converts it to depth.
• Velocity: speed of the pulse in the ground: 0.3 m/ns divided by the square root of relative permittivity, found by fitting hyperbolas.

GNSS and survey terms

These cover satellite positioning, levelling and the coordinate systems in which drawings are delivered. In India almost every modern survey ends up on WGS84 and a UTM zone, so those two are worth reading first.

• Auto level: an optical level whose compensator keeps the line of sight horizontal; it carries heights from a benchmark to new points.
• Base station: a GNSS receiver set on a point of known coordinates that supplies corrections to one or more rovers.
• Benchmark (BM): a permanent mark of known height, the starting value for levelling.
• CORS: continuously operating reference stations; Survey of India runs a national network that streams corrections.
• Datum: the reference to which coordinates or heights are tied, such as WGS84 for position or mean sea level for height.
• DGPS: differential GPS, correcting a receiver with data from a reference on a known point. In Indian contracts the term often covers base-and-rover carrier-phase work.
• Easting and northing: grid coordinates in metres east and north of a projection's origin.
• Ellipsoidal height: height above the reference ellipsoid, which is what GNSS measures; it differs from height above sea level by the geoid separation.
• Fixed and float: status of an RTK solution: fixed when carrier ambiguities are resolved and accuracy is centimetric, float when they are not.
• Geoid: the level surface that best matches mean sea level, used as the reference for orthometric heights.
• GNSS: the family of satellite positioning systems, GPS, GLONASS, Galileo, BeiDou and regional ones such as NavIC.
• Ground control point (GCP): a surveyed target visible in drone images that ties the photogrammetric model to real coordinates.
• NTRIP: the protocol that streams GNSS corrections over the internet, so a rover can work from a network over mobile data.
• PDOP: position dilution of precision, a number describing satellite geometry; lower values mean a stronger fix.
• Reduced level (RL): the height of a point above the adopted datum, as written on level sheets and drawings.
• RTK: real time kinematic positioning, centimetre fixes in the field from carrier-phase corrections.
• Static survey: GNSS observation over a long session, processed afterwards; the most accurate way to fix primary control.
• Total station: an electronic instrument measuring angles and distances; ours measure distance to 5 mm + 3 ppm.
• Traverse: a chain of stations fixed by angles and distances, closed on known points so its error can be checked.
• UTM zone: one of the 6-degree strips of the Universal Transverse Mercator grid; India spans zones 42N to 47N.
• WGS84: the global datum and ellipsoid used by GPS, and the basis of most coordinates delivered today.

Land record terms in Haryana, Punjab and Uttar Pradesh

Revenue vocabulary differs by state, so each definition below says where it applies. Haryana and Punjab share a system rooted in the Punjab Land Revenue Act, 1887 and the consolidation of holdings; Uttar Pradesh uses different names for similar records. Official copies always come from the revenue department, and a private survey drawing does not replace official demarcation.

• Abadi / lal dora: the old residential core of a village inside the lal dora line, traditionally kept out of detailed ownership records in Haryana and Delhi.
• Bigha: a traditional area unit whose size changes from state to state and sometimes district to district, so always confirm the local value.
• Fard / nakal: a certified copy of a jamabandi entry, issued by the revenue office.
• Gata number: the plot number used in Uttar Pradesh village records.
• Intkal (mutation): the revenue entry that changes the recorded owner after a sale, inheritance or partition, once sanctioned by a revenue officer.
• Jamabandi: the record of rights for agricultural land in Haryana and Punjab, prepared by the patwari.
• Kanal: one-eighth of an acre, 20 marla or about 5,445 sq ft, in Haryana and Punjab revenue measure.
• Karam: the linear unit in Haryana and Punjab field measurement, normally 5.5 ft; some older settlements used a shorter karam.
• Khasra: the number of a field on the village map, used in every revenue record that mentions it.
• Khatauni: in Haryana and Punjab, the cultivation holding number inside the jamabandi; in Uttar Pradesh, the name of the record of rights itself.
• Khewat: the ownership holding number in a Haryana or Punjab jamabandi.
• Killa: in consolidated villages, a field of about one acre within a rectangle, written as rectangle//killa.
• Marla: one-twentieth of a kanal; in Haryana and Punjab revenue measure 9 square karam, or 272.25 sq ft.
• Murabba / mustatil: the 25-acre rectangle of 25 killas laid out during consolidation of holdings.
• Nishandehi: official demarcation of boundaries on the ground by revenue staff, working from the records.
• Patwari: the village revenue official who keeps the jamabandi and village map; the equivalent post in Uttar Pradesh is the lekhpal.
• Shajra: the village revenue map (shajra kishtwar). Shajra nasab, a different document, is the family tree of the owners.
• Tatima: a supplementary sketch showing how a field was divided into new numbers.

Utility practice and SUE terms

These are the words of damage prevention, utility detection and coordination, from first record search to the final as-built. Several come from US and UK practice and are used on Indian projects in the same sense.

• As-built drawing: the measured record of a service as it was laid, with depths, pits and crossings.
• ASCE 38: the American Society of Civil Engineers guideline for investigating and documenting existing utilities, currently ASCE 38-22, which defines quality levels D to A.
• Call Before u Dig: the Department of Telecommunications app that connects excavating agencies with owners of underground assets.
• Colour code: the marking colours for services. The US APWA code uses red for power, orange for communication, yellow for gas and oil, blue for drinking water and green for sewers; India has no single national code.
• Direct connection: clipping a locator transmitter to a metallic pipe, cable sheath or tracer wire, with an earth stake to complete the circuit.
• Electromagnetic locator: a receiver that detects the magnetic field around a conductor carrying current, either already present or applied by a transmitter.
• HDD: horizontal directional drilling: a steered pilot bore, then reaming and pullback of the pipe or duct, without an open trench.
• Active and passive locating: following a signal you apply yourself, or listening for fields already on the line.
• Quality level (QL): the reliability grade of utility information: QL-D from records, QL-C from surface features, QL-B from geophysics, QL-A from exposure. Our SUE quality levels A–D for Indian projects guide explains each.
• Signal clamp: a coupler placed round a cable to induce the transmitter signal into that cable alone.
• Sonde: a small transmitter pushed or drilled through a line so it can be traced from the surface.
• SUE: subsurface utility engineering: managing the risk of underground utilities through records, locating, exposure and documentation.
• Shapefile and KMZ: two common formats for delivering mapped utility lines, one for GIS analysis and one for viewing.
• Tolerance zone: the hand-dig strip either side of a marked service.
• Tracer wire: a copper wire laid with plastic pipes or ducts so they can be located by direct connection.
• Trial pit: an excavation dug by hand or machine to expose and measure a service.
• Utility conflict matrix: the register of clashes between a design and existing services, with the agreed fix for each.
• Vacuum excavation: exposing a service with an air or water lance and suction, the usual way to reach QL-A.

Glossary at a glance

Four groups, each tied to a different stage of a project.

Radar terms are easiest to follow beside an image; the Mezux guide: B-Scan in GPR shows how a section is read.

How to use these terms with a survey brief

Name the deliverable, the coordinate system and the confidence you need, and most misunderstandings disappear. Take a brief that says "GPR survey to QL-B, depths stated with velocity, coordinates in WGS84 / UTM 43N, as-built style drawing in DWG and KMZ". It leaves little room for argument later. For land, quote the village, khasra or rectangle//killa numbers and attach a recent jamabandi copy.

If a word you need is missing from this GPR glossary, tell us and we will add it. To turn a brief into a priced scope, get a written quote for your project.

Frequently asked questions

How deep can GPR see?

It depends on antenna frequency and soil: a few metres for utility antennas in good ground, much less in wet clay. For the details, read GPR Depth of Penetration.

Where can I see real radar images?

We keep labelled scans from many soils and sites; see: GPR Radargram Library.

Are the land record terms the same in every state?

No. Haryana and Punjab share terms such as jamabandi, khewat and killa; Uttar Pradesh uses khatauni and gata numbers, and other states differ again.

What is the difference between SUE and a GPR survey?

GPR is one tool used to detect and map services. SUE is the whole process of researching, locating, exposing and documenting buried services to a stated quality level.

Why do survey drawings mention WGS84 and UTM?

WGS84 is the datum behind GNSS coordinates and UTM turns them into metre grids; both must be stated so coordinates can be reused.

Can you add a term that is missing?

Yes. Send us the word and where you met it, and we will add a definition.

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