Drone Survey and Inspection Glossary

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3D mapping and modelling: A service that surveys a land area or structure and produces an accurate 3D map or structural model of it, usually built from a point cloud captured by drone photogrammetry or laser scanning. See digital topographical surveying

A

A2 CofC: The A2 Certificate of Competency, a UK CAA qualification that lets a remote pilot fly certain drones closer to uninvolved people than the standard open category limits allow. See the team behind DTA
Accelerometer: A sensor that measures a drone's acceleration in a given direction, helping the flight controller hold a stable, level flight.
Acro mode: A manual flight control mode for experienced pilots that switches off automatic self levelling, allowing full control over the drone's attitude. Not used on DTA commercial survey and inspection flights.
Aerial photography: Photography taken from a camera mounted on a drone, an elevated mast, or a manned aircraft or helicopter. See construction media and project progress services
Aerial video and film: Video or film shot from a camera mounted on a drone, an elevated mast, or a manned aircraft or helicopter. See construction media and project progress services
AGL, AIP and ASL: Three ways of measuring drone altitude. Above Ground Level (AGL) is height above the ground directly below the drone, Above Initiation Point (AIP) is height above the take off point, and Above Sea Level (ASL) is height above mean sea level.
ATEX: The name commonly given to the two European directives that control equipment and workplaces where explosive atmospheres may occur. Equipment used near such atmospheres needs an ATEX rating. See the team behind DTA
Atti mode: Attitude mode, a flight control mode where the pilot manually controls pitch and roll while the flight controller holds altitude and heading automatically. Often used for aerial photography.
Autonomous flight: Flight in which the drone's own navigation system, using GPS, obstacle sensing or inertial navigation, controls the aircraft without constant manual input from the pilot.
Autopilot: Flight control software that flies a drone along a pre planned automated route, or holds it in a stationary hover at a set height. Used in many DTA surveying and inspection flights. See digital topographical surveying
AUV: An Autonomous Underwater Vehicle, a submersible craft that operates underwater without a person on board or a control tether.
AW (Aerial Work): One of the International Civil Aviation Organisation's three categories of civil aviation operation, covering activities such as photography, surveying, observation and patrol carried out from the air. See the team behind DTA
Axis: A plane of flight. Most drones are controlled across at least four axes, with six or more axes of sensing preferred for stability.

B

BIM: Building Information Model, a digital model of a building's physical and functional characteristics used as a shared reference through its design, construction and operating life. Drone measured building surveys are a common way to capture the data for a BIM. See measured building surveys
BVLOS: Beyond Visual Line of Sight, flying a drone further than the pilot can see and control unaided. UK operators need specific CAA permission to fly BVLOS; standard flights are limited to Visual Line of Sight. See the team behind DTA

C

CAA: The UK Civil Aviation Authority, the government body responsible for regulating the use of drones and all aircraft in UK airspace. See the team behind DTA
CAA Operational Authorisation: The CAA permission scheme for commercial and higher risk drone operations in the UK, held by an operator alongside remote pilot qualifications such as the GVC. It replaced the older Permission for Commercial Operation (PfCO) in 2021. See the team behind DTA
CAT (Commercial Air Transport): An aircraft operation that transports passengers, cargo or mail for payment, one of the three civil aviation categories defined by the International Civil Aviation Organisation alongside General Aviation and Aerial Work. See the team behind DTA
Commercial flight: Flying a drone for business purposes. In the UK this is regulated by the CAA and requires the operator to hold a CAA Operational Authorisation. See the team behind DTA

D

Drone: An uncrewed vehicle capable of programmed or autonomous operation. The term can describe a terrestrial, aerial or aquatic remote controlled system, though it is now most commonly used for an aerial one.
Drone chimney inspection: A visual inspection of a chimney or stack carried out by a drone in place of scaffolding, rope access or a cherry picker. See commercial drone inspection services
Drone fugitive methane gas survey: A survey of a land area, building or industrial site that measures fugitive methane gas levels at set points on a grid, using a sensor carried by the drone. See commercial drone inspection services
Drone inspection: An inspection of a structure or object carried out by a drone, typically using high resolution photography or video, and sometimes other sensors such as a thermal camera or a contact ultrasonic sensor. See commercial drone inspection services
Drone internal confined space inspection: The inspection of an internal confined space, such as a tank, vessel or duct, using a drone fitted with a protective cage and additional navigation systems for flying without GPS. See confined space drone inspections
Drone measured building survey: A measured building survey carried out with a drone, producing a point cloud from which an accurate, measurable 3D model of the building is generated. See measured building surveys
Drone roof inspection: A visual inspection of a roof carried out by drone, recording coverings, ridges, valleys, flashings and rainwater goods without routine work at height. See drone roof surveys
Drone survey: At DTA we reserve the word survey for work where height, width, depth or GPS location is measured, such as topographical surveying and 3D mapping, as distinct from a visual inspection. See digital topographical surveying
DSLR: A digital single lens reflex camera, which combines the optics and mechanism of a traditional single lens reflex camera with a digital imaging sensor rather than film. See construction media and project progress services
DSM (Digital Surface Model): A 3D model of the ground and everything on it, including buildings, structures and vegetation, generated from drone survey data. See digital topographical surveying
DTM (Digital Terrain Model): A 3D model of the bare ground surface with buildings, structures and vegetation removed, used for contours, drainage design and earthworks planning. See digital topographical surveying

E

EASA: The European Union Aviation Safety Agency, the body responsible for civil aviation safety regulation across the European Union. See the team behind DTA
Elevated MAST: A large mast, typically over 15 metres, raised and lowered pneumatically with a remote controlled pan tilt zoom camera on top, used for aerial photography and video where a drone is not suitable. See construction media and project progress services
Elevated MAST photography: Aerial photography captured using an elevated mast rather than a drone, for example in restricted airspace or where continuous ground level control is preferred. See construction media and project progress services
Elevated MAST video and film: Aerial video or film captured using an elevated mast rather than a drone. See construction media and project progress services

F

FAA: The United States Federal Aviation Administration, the body responsible for civil aviation regulation in the United States. See the team behind DTA
FPV: First person view, a feature that streams live video from the drone's camera to the pilot's controller or screen, giving the pilot the drone's own viewpoint during flight.
FRZ (Flight Restriction Zone): The controlled airspace around a licensed UK aerodrome where extra permission from air traffic control or the aerodrome is normally needed before flying a drone. See the team behind DTA

G

GA (General Aviation): The private, recreational and business flying component of aviation, one of the three civil aviation categories used by the International Civil Aviation Organisation. See the team behind DTA
GCP (Ground Control Point): A marked point on the ground with a known, surveyed location, visible in the drone's aerial photographs. Ground control points tie the survey data to real world coordinates and are needed for accurate mapping even where RTK is used. See digital topographical surveying
Gimbal: A motorised mounting that attaches a sensor, such as a camera or LiDAR unit, to a drone and holds it steady or points it in a chosen direction during flight. See construction media and project progress services
GNSS: Global Navigation Satellite System, the generic term for a satellite system used to measure a receiver's geographic location anywhere in the world. GPS and the Russian GLONASS system are both GNSS systems. See digital topographical surveying
GNSS receiver: An electronic device that receives and processes signals from a navigation satellite constellation to measure the accurate geographic location of points on the ground during a survey. See digital topographical surveying
GPS: The Global Positioning System, the United States' satellite navigation system and the GNSS system most people mean when they say GPS. See digital topographical surveying
GSD (Ground Sample Distance): The real world distance on the ground represented by one pixel in an aerial photograph. A smaller GSD means a higher resolution survey. GSD is related to flying height, so a lower flight gives a smaller GSD for a given camera. See digital topographical surveying
GVC (General VLOS Certificate): The UK remote pilot qualification most commercial drone operators hold to support their CAA Operational Authorisation for standard visual line of sight flights. See the team behind DTA

H

Headless mode: A flight mode where the drone always moves toward or away from the controller rather than relative to its own front and back, regardless of which way it is facing.
Hexacopter: A drone with six rotors, sometimes called a hex drone.
HSE: Two related abbreviations: the UK Health and Safety Executive, the government authority for workplace safety, and health, safety and environmental, the term used in company policies and job titles. See the team behind DTA
HSE-MS: A Health, Safety and Environmental Management System, the documented set of policies and procedures a company uses to manage risk across its operations. See the team behind DTA

I

ICAO: The International Civil Aviation Organisation, which defines civil aviation operations in three categories: General Aviation, Aerial Work and Commercial Air Transport. See the team behind DTA
IFR: Instrument Flight Rules, flying an aircraft using instrument readouts alone rather than visual reference to the ground. UK drone flights are currently conducted under Visual Flight Rules instead. See the team behind DTA
IMU: An Inertial Measurement Unit, an electronic module that measures angular velocity and acceleration, typically using accelerometers and gyroscopes. IMUs help a drone hold its attitude and navigate indoors where GPS does not work.
Inertial navigation system (INS): A system that calculates a drone's position from an initial GPS fix and then from accelerometer and motion sensor data when GPS is unreliable or unavailable, such as inside a building.

L

LiDAR: A method of measuring distance by illuminating a target with laser light and timing the reflection, used to build detailed 3D representations of the ground or a structure. LiDAR is used in surveying, archaeology and forestry as well as drone terrain following. See digital topographical surveying
LiPo battery: A lithium polymer battery, the type used in almost all drones because it is lighter than other rechargeable battery types for the same capacity.

M

mAh: Milliampere hour, the unit used to state a drone battery's electrical charge capacity. A higher mAh figure generally means a longer flight time, within the limits the airframe can carry.
Measured building survey (MBS): A survey where a laser scanner, a drone, or both together, measure a large number of points on a building's walls, roof and structural elements, creating a point cloud and an accurate, measurable 3D model. See measured building surveys
MTOM and MTOW: Maximum take off mass and maximum take off weight, the heaviest a drone is permitted to be, including its payload, at the point it takes off.
Multi-copter: A generic term for a drone with more than one rotor, covering quadcopters, hexacopters, octocopters and similar aircraft.

N

NAS: National Airspace System, a term, mostly used in the United States, for the network of airspace, air navigation facilities, procedures and regulations that governs a country's aviation. See the team behind DTA
NDVI: Normalized Difference Vegetation Index, a measure of vegetation health calculated from the difference between the near infrared and red light a plant reflects. Used in precision agriculture and estate land survey work to assess crop and vegetation condition. See digital topographical surveying
NEBOSH: The National Examination Board in Occupational Safety and Health, the UK body that sets qualifications and examinations for health and safety management. See the team behind DTA
No fly zone: An area where flying a drone is restricted by regulation, typically because of the risk to other aircraft, or because sensitive sites or activities are nearby. See the team behind DTA
NOTAM: A Notice to Airmen, a notice issued to pilots about the establishment, condition or change of an aeronautical facility, service, procedure or hazard, such as a temporary flight restriction. See the team behind DTA

O

Octocopter: A drone with eight rotors, giving extra lift and a level of redundancy if one motor fails during flight.
Orthomosaic: A single, geometrically corrected aerial image made by stitching together many overlapping photographs from a drone survey, with a uniform scale across the whole image like a map. See digital topographical surveying
OSC (Operational Safety Case): A set of safe operating procedures written by a drone operator and then submitted to, audited and approved by the CAA, which permits operations outside the standard limits, such as reduced distances from people or buildings, or BVLOS flight. See the team behind DTA

P

Payload: The additional weight a drone can carry beyond its own airframe and battery, such as a camera and gimbal.
PfCO: Permission for Commercial Operation, the CAA authorisation UK operators previously needed to fly drones commercially. It was replaced by the current CAA Operational Authorisation scheme in 2021. See the team behind DTA
Photogrammetry: The process of calculating measurements from photographs, particularly the precise position and elevation of points on the ground, used to build orthomosaics, point clouds and 3D models from drone imagery. See digital topographical surveying
PIC (Pilot in Command): The pilot responsible for, and in overall command of, a drone flight or operation, sometimes referred to as pilot in control. See the team behind DTA
Point cloud: A set of data points in space that together describe the surfaces of the land or an object. In the drone industry point clouds come from photogrammetry or LiDAR, and are used to build measurable 3D models for surveys and volume calculations. See digital topographical surveying
PPK (Post Processed Kinematic): A satellite positioning technique similar to RTK, where the correction data is applied to the drone's GPS log after the flight rather than in real time, improving position accuracy without needing a live radio link during flight. See digital topographical surveying
PPSM: Points per square metre, a measure of how dense the data points in a point cloud are. A higher PPSM figure generally means finer surveyed detail. See digital topographical surveying

Q

Quad-copter: A drone with four rotors, the most common configuration for commercial survey and inspection drones.

R

Radio controller: The handheld device used to fly a drone, typically with two joysticks controlling tilt, direction, take off and landing, and sometimes a built in screen for a first person view.
RAMS: A Risk Assessment and Method Statement, the documents that identify the risks on a specific site and set out how they will be managed. Every DTA project has a RAMS document supplied to the client and to personnel on site. See the team behind DTA
ROV / ROVER: A Remotely Operated Vehicle, a terrestrial or aquatic robotic vehicle used for inspection in places a person or an aerial drone cannot easily reach, such as a culvert or a submerged structure. See confined space drone inspections
RPAS: Remotely Piloted Aircraft System, a term favoured by aviation authorities that is broadly equivalent to UAS and often appears in regulatory and legal documents. See the team behind DTA
RTF: Ready to fly, a UAV supplied with all the basic equipment needed to fly it, such as a battery, charger and controller, requiring minimal assembly.
RTK: Real Time Kinematic, a satellite navigation technique that uses a fixed base receiver and a rover receiver together to sharply increase the precision of GPS position data during a survey. See digital topographical surveying

T

Telecommunication line of sight survey: A survey that confirms there is a direct, unobstructed path between two proposed locations for directional telecommunications or microwave dishes, carried out using a drone or an elevated mast. See digital topographical surveying
TOAL zone: A take off and landing zone, the area a drone operator clears and controls for launching and recovering the aircraft during a flight. See the team behind DTA
Topographical land survey: A survey that measures and records the exact location of natural and manmade features on an area of land, such as ground contours, boundaries, buildings, drainage, services and vegetation, delivered as a CAD plan. See digital topographical surveying
Transmitter: An electronic component that sends signals between the drone and the ground, either for control or for telemetry data.

U

UAS: An Unmanned Aircraft System, the whole system that makes a drone work, including the aircraft, ground control equipment, GPS module, transmission systems, camera, software and the remote pilot on the ground. See the team behind DTA
UAV: An Unmanned Aerial Vehicle, a device that can propel itself through the air without a pilot on board. Aerial drones and quadcopters are UAVs. See the team behind DTA
Ultrasonic sensor: Either a sensor that measures a drone's height above ground or distance from obstacles by reflecting sound waves, or a contact sensor pressed against a metal structure to measure thickness or detect fatigue and damage, often called a UT sensor. See commercial drone inspection services

V

VFR: Visual Flight Rules, flying an aircraft with visual reference to the ground, other aircraft and obstacles. UK drones must currently be flown under VFR unless operating under a BVLOS exemption. See the team behind DTA
VLOS: Visual Line of Sight, keeping the drone within the pilot's unaided sight at all times during flight, currently required in the UK at up to 500 metres unless a BVLOS exemption applies. See the team behind DTA
VTOL: Vertical Take Off and Landing. Fixed wing VTOL drones take off and land vertically like a helicopter before flying forward like a plane; multi rotor drones also take off and land vertically by design.

W

Waypoint control: Flying a drone along a series of pre programmed locations, typically GPS coordinates, rather than under continuous manual control.

Drone survey and inspection glossary

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