UK Drone Laws

Drone Jargon Buster: Drone Survey and Construction Terms Explained

This drone jargon buster explains the terminology, abbreviations and acronyms used in drone surveying and the wider construction industry, from BVLOS, GSD and A2 CofC through to point clouds, orthomosaics and digital twins. Each entry gives a plain-English definition plus a note on how the term is used on site, so you can read a survey quote, specification or deliverables list without needing a translator.

We keep this page updated as CAA rules and survey technology change. If there’s a term you use that we haven’t covered, email us using the details at the bottom of the page and we’ll add it.

A

A1, A2, A3
The three sub-categories of the Open Category, now given plain-English names by the CAA: Over People (A1), Near People (A2) and Far from People (A3). Which one you can fly in depends on the drone's class mark and the pilot's qualification.
A2 CofC
A2 Certificate of Competency. A CAA-recognised qualification allowing a remote pilot to fly closer to uninvolved people in the A2 sub-category. A UK2-class drone can operate as close as 5 metres to uninvolved people in low-speed mode when the pilot holds an A2 CofC.
AAIB
Air Accidents Investigation Branch. The UK body that investigates civil aviation accidents, including those involving unmanned aircraft.
AGL
Above Ground Level. Height measured from the ground directly beneath the aircraft. The UK Open Category limit is 120m AGL.
AMSL
Above Mean Sea Level. Height measured from sea level, used in aviation charts and airspace descriptions rather than for drone height limits.
ANO
Air Navigation Order. The principal piece of UK aviation legislation governing how aircraft, including drones, may be flown.
ARPAS-UK
Association of Remotely Piloted Aircraft Systems UK. The UK trade association for the commercial drone industry.
As-Built
A drawing or model recording what was actually constructed, as opposed to what was designed. Drone surveys are frequently used to produce as-built records for verification against design.
Assembly of People
A gathering where individuals cannot move away to avoid a falling drone. Flying over an assembly is prohibited in the Open Category.
ATC
Air Traffic Control. The service that manages aircraft movements. Drone operations inside controlled airspace usually require ATC permission.
ATTI
Attitude Mode. A flight mode in which the aircraft holds altitude but not position, so it drifts with the wind. Used when satellite positioning is degraded, typically close to large structures.
Atypical Air Environment
Airspace where manned aircraft are very unlikely to be encountered, such as immediately alongside a building, bridge or wind turbine. Commonly used to justify lower-risk BVLOS inspection work.
ATZ
Aerodrome Traffic Zone. Protected airspace around an aerodrome, typically 2 or 2.5 nautical miles in radius up to 2,000ft.

B

BIM
Building Information Modelling. A shared digital model of a building's geometry and data. Drone-derived point clouds and meshes are often imported into BIM workflows.
Building Safety Act 2022
UK legislation introducing stricter duties for higher-risk buildings, including the requirement to maintain accurate building information throughout the lifecycle.
BVLOS
Beyond Visual Line of Sight. Flying where the remote pilot cannot see the aircraft unaided. BVLOS operations require an Operational Authorisation obtained through UK SORA.

C

CAA
Civil Aviation Authority. The UK regulator for all aviation, including drones.
CAP
Civil Aviation Publication. CAA guidance documents. The ones that matter most to drone work are CAP 722 (UAS policy and guidance), CAP 2320 (the Drone and Model Aircraft Code) and CAP 2606 (the PDRA01 operations manual template).
CDM 2015
Construction (Design and Management) Regulations 2015. The regulations governing health and safety duties on UK construction projects. Drone surveys are often specified as a way of discharging the duty to avoid working at height.
Certified Category
The highest-risk regulatory category, used for operations comparable to manned aviation, such as carrying passengers. Almost no survey work falls into it.
Class Marking (UK0 to UK6)
The UK product standard labelling system for drones, covering performance and reliability, geo-awareness, Remote ID and flashing lights. From 1 January 2026, all drones placed on the UK market carry a UK class mark, with existing EU C-class marks recognised as the equivalent UK class until 31 December 2027.
Congested Area
An area substantially used for residential, commercial, industrial or recreational purposes. Survey work in congested areas normally sits in the Specific Category.
Contours
Lines joining points of equal elevation on a survey drawing, generated from drone-derived terrain models at a specified interval.
CSCS Card
Construction Skills Certification Scheme card. Proof of site safety training, routinely required before a pilot is allowed onto a live construction site.

D

DEM
Digital Elevation Model. A general term for a raster model of surface heights, covering both DSM and DTM outputs.
Digital Twin
A geometrically accurate digital replica of a building or asset, kept current through repeat capture, and used for inspection, planning and maintenance without revisiting site.
Dilapidations
An assessment of a property's condition against lease obligations. Aerial imagery is used to evidence roof and high-level defects that cannot be seen from the ground.
Drone and Model Aircraft Code
The CAA's plain-English rulebook (CAP 2320) for Open Category flying, covering height limits, distances from people and where flying is prohibited.
DSM
Digital Surface Model. A height model of everything the sensor sees, including roofs, plant and vegetation.
DTM
Digital Terrain Model. A height model of the bare ground with buildings and vegetation removed. This is what most topographical drawings are built from.

E

Emissivity
A material's efficiency at emitting infrared radiation. Setting it correctly is essential for accurate temperature readings in a thermal survey.
EVLOS
Extended Visual Line of Sight. Operating with trained observers maintaining visual contact with the aircraft on the remote pilot's behalf.

F

Flight Log
The record of each flight, including aircraft, pilot, duration and location. Required evidence of currency and compliance under an Operational Authorisation.
Flyer ID
The CAA identifier issued after passing the online theory test. From 1 January 2026 a Flyer ID is required for drones and model aircraft weighing 100g or more.
FPV
First Person View. Flying using the live video feed from the aircraft rather than direct visual contact.
FRZ
Flight Restriction Zone. The protected airspace around a UK aerodrome, extending from the ATZ boundary plus runway protection zones. Permission from the aerodrome is needed before flying inside it.

G

GCP
Ground Control Point. A marked target on the ground with a precisely surveyed coordinate, used to georeference a photogrammetric model and verify its accuracy.
Geo-awareness
A drone function that warns the pilot when the aircraft approaches restricted airspace, and a requirement of the UK class marking standards.
Georeferencing
Tying survey data to a real-world coordinate system so it aligns with existing site drawings and mapping.
GIS
Geographic Information System. Software for storing, analysing and displaying spatially referenced data.
GNSS
Global Navigation Satellite System. The umbrella term covering GPS, GLONASS, Galileo and BeiDou. More accurate than “GPS” when describing a drone's positioning.
Golden Thread
The requirement under the Building Safety Act to hold accurate, accessible building information for higher-risk buildings across their lifecycle.
GPS
Global Positioning System. The US satellite constellation, and the term most commonly used in place of GNSS.
GSD
Ground Sample Distance. The real-world size of one image pixel, usually expressed in mm per pixel. It determines the smallest defect a survey can resolve, so it is the single most useful number in a survey specification.
GVC
General Visual Line of Sight Certificate. The standard remote pilot qualification for Specific Category operations, required before an operator can apply for an Operational Authorisation.

H

HSE
Health and Safety Executive. The UK regulator for workplace health and safety, including work at height.

I

IMU
Inertial Measurement Unit. The accelerometer and gyroscope package that senses the aircraft's orientation and motion.

K

KML / KMZ
File formats for geographic data, widely used to share flight areas, site boundaries and survey extents in mapping software.

L

LAS / LAZ
The standard open file formats for point cloud data. LAZ is the compressed version of LAS.
Legacy Drone
A drone without a UK or EU class mark, subject to weight-based rather than class-based rules during the transition period.
LiDAR
Light Detection and Ranging. A sensor that measures distance with laser pulses. It captures ground beneath vegetation, which photogrammetry cannot, but costs more to fly and process.
LOD
Level of Detail, also used as Level of Development. The agreed richness of a model deliverable, which should be set before capture rather than after.

M

MEWP
Mobile Elevating Work Platform. A cherry picker or scissor lift used to reach height. Drone inspection is usually specified as the safer and cheaper alternative, avoiding road closures, ground loading checks and operator access training.
MOR
Mandatory Occurrence Report. The formal report submitted to the CAA following a safety-related event.
MTOM
Maximum Take-Off Mass. The total mass of the aircraft including batteries and payload. It determines which class and sub-category rules apply.

N

NATS
The UK's main air navigation service provider, responsible for controlling airspace and providing air traffic services.
NDT
Non-Destructive Testing. Inspection that does not damage the asset. Thermal and visual drone surveys are a form of it.
NOTAM
Notice to Airmen. A notice giving essential information about airspace hazards or restrictions, which should be checked as part of pre-flight planning.

O

Open Category
The lowest-risk regulatory category, requiring no CAA authorisation but subject to strict limits on height, proximity to people and aircraft class.
Operational Authorisation
The CAA permission that allows Specific Category operations. It is issued to the UAS operator rather than an individual pilot, is normally valid for 12 months, and permits only the operations written into the accompanying operations manual. This is the correct term for what many clients still call a “drone licence”.
Operations Manual
The document setting out an operator's procedures, aircraft, emergency responses and limitations. It underpins the Operational Authorisation and should be requested when procuring a survey.
Operator ID
The registration number issued to whoever is responsible for the drone, displayed on the aircraft. Required for drones of 100g or more with a camera, or 250g or more without one.
Orthomosaic
A composite aerial image corrected for lens distortion and terrain so that scale is consistent throughout, allowing measurements to be taken directly from it. Often called an orthophoto or ortho.
OSGB36 / OSTN15
The Ordnance Survey national grid datum and transformation used to align survey data with UK mapping.

P

Payload
The sensor or equipment the aircraft carries, such as an RGB camera, thermal camera or LiDAR unit.
PDRA01
Pre-Defined Risk Assessment 01. The standard route to an Operational Authorisation, covering VLOS flying with drones between 250g and 25kg, subject to a 120m ceiling, a 50m buffer from uninvolved people reducing to 30m for take-off and landing, and a 500m maximum range from the remote pilot.
Permit to Work
A formal written authorisation to carry out specified work in a controlled area, often required before flying on operational or industrial sites.
Photogrammetry
The technique of deriving measurements and 3D geometry from overlapping photographs. The basis of most drone survey deliverables.
PIC
Pilot in Command. The person responsible for the safe conduct of the flight, referred to in UK drone regulation as the remote pilot.
Point Cloud
A dense set of measured 3D points representing a surface, produced by photogrammetry or LiDAR and used to generate elevations, sections and models in CAD.
PPE
Personal Protective Equipment. Site-standard safety wear, which drone crews are expected to hold and use like any other contractor.

R

RAAC
Reinforced Autoclaved Aerated Concrete. A lightweight concrete used in roof planks between the 1950s and 1990s, now known to deteriorate. Aerial inspection is used to assess roof condition and locate panels without loading the structure.
RAMS
Risk Assessment and Method Statement. The combined document explaining the hazards of a job and the safe system of work for carrying it out. Most sites require RAMS before a drone crew is allowed to mobilise, and a site-specific set should be produced for every survey rather than a generic template.
Reality Capture
The general term for recording existing conditions digitally through photogrammetry, LiDAR or laser scanning.
Remote ID
Broadcast identification, effectively a digital number plate transmitting the operator ID, serial number and position during flight. Mandatory for UK1, UK2, UK3, UK5 and UK6 class drones from 1 January 2026, and for legacy and UK0 drones of 100g or more with a camera from 1 January 2028.
Remote Pilot
The individual operating the flight controls. The current legal term, replacing older references to the drone pilot and operator as one and the same.
RGB
Red, Green, Blue. Standard visible-light imagery, as distinct from thermal or multispectral capture.
RICS
Royal Institution of Chartered Surveyors. The professional body for surveyors, whose standards govern many building survey deliverables.
RPAS
Remotely Piloted Aircraft System. An alternative term for UAS, more common in aviation and defence than in UK regulation.
RTK
Real-Time Kinematic. A satellite correction technique giving centimetre-level positioning in flight, reducing or removing the need for ground control points.

S

SAIL
Specific Assurance and Integrity Level. The risk score from 1 to 6 assigned to an operation under SORA, with complexity and cost rising as the score increases.
Schedule of Condition
A dated photographic record of a property's condition at a point in time, used to evidence pre-existing defects before works begin or a lease is signed.
Snagging
Identifying defects in newly completed construction before handover. Aerial capture covers roofs, gutters and upper elevations that a ground-level snag list misses.
SORA
Specific Operations Risk Assessment. UK SORA is the bespoke risk assessment route to an Operational Authorisation for operations beyond PDRA01, and it replaced the Operating Safety Case method on 23 April 2025.
Specific Category
The middle regulatory category, covering operations beyond Open Category limits and requiring an Operational Authorisation. Most commercial survey work sits here.
SUA
Small Unmanned Aircraft. An unmanned aircraft of 20kg or less, the term used in the Air Navigation Order.

T

Thermography
Thermal imaging. Surveying with an infrared sensor to detect heat loss, moisture ingress, flat roof saturation and faulty solar panel cells.
Tie Point
A feature identified across multiple overlapping images, used by photogrammetry software to align them into one model.
Topographical Survey
A measured survey recording levels, features and boundaries across a site, supplied as a CAD drawing for design work.

U

UAS
Unmanned Aircraft System. The aircraft plus its control equipment. The term used throughout UK regulation.
UAS Operator
The person or organisation legally responsible for the drone and its operations, and the holder of the Operational Authorisation. This is usually the company, not the pilot.
UAV
Unmanned Aerial Vehicle. The aircraft itself. Still widely used commercially, though UAS is the correct regulatory term.
Uninvolved Person
Anyone not participating in or briefed on the drone operation. Separation distances in the regulations are measured from these people.

V

VLOS
Visual Line of Sight. Flying where the remote pilot can see the aircraft unaided at all times, normally taken as up to 500m horizontally.
Volumetric Survey
Measuring the volume of a stockpile, void or excavation from a 3D survey model, typically for material reconciliation or earthworks valuation.

W

Waypoint
A pre-programmed coordinate in an automated flight plan, used to make repeat surveys of the same site directly comparable.
WGS84
The global coordinate system used by GNSS, which must be transformed to OSGB36 for UK site drawings.
Working at Height Regulations 2005
The regulations requiring employers to avoid work at height where reasonably practicable. The legal basis for most of the case for drone inspection over scaffold, ladders and MEWPs.

Busting the Industry Jargon