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Drone Jargon BusterDrone 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.
98 termsUpdated for 2026 CAA rulesPlain-English definitions
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. UK drone laws →
- 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. UK drone laws →
- 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. Our accreditations →
- 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. Measured surveys →
- 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. Measured surveys →
- 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. UK drone laws →
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. UK drone laws →
- 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. Our accreditations →
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. Measured surveys →
- 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. Building surveys →
- 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. UK drone laws →
- 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. Thermal surveys →
- 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. UK drone laws →
- 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. UK drone laws →
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. UK drone laws →
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. UK drone laws →
- 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. Measured surveys →
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. Roof surveys →
- 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. UK drone laws →
- 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”. Our accreditations →
- 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. UK drone laws →
- 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. Measured surveys →
- 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. UK drone laws →
- 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. Measured surveys →
- 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. RAAC surveys →
- 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. Our accreditations →
- Reality Capture
- The general term for recording existing conditions digitally through photogrammetry, LiDAR or laser scanning. Measured surveys →
- 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. UK drone laws →
- 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. Building surveys →
- Snagging
- Identifying defects in newly completed construction before handover. Aerial capture covers roofs, gutters and upper elevations that a ground-level snag list misses. Thermal snagging →
- 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. UK drone laws →
- Specific Category
- The middle regulatory category, covering operations beyond Open Category limits and requiring an Operational Authorisation. Most commercial survey work sits here. UK drone laws →
- 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. Thermal surveys →
- 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. Measured surveys →
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. UK drone laws →
- 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.
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