Glossary Of Terms

Absolute Accuracy

Refers to the accuracy of a point related to the coordinates in the real world. Absolute Accuracy means that a point on a map should match its actual GPS coordinates.

Air Traffic Control (ATC)

A service provided by ground-based controllers who direct aircraft on the ground and through controlled airspace, and can provide advisory services to aircraft in non-controlled airspace.

Building Information Modelling (BIM)

A process for creating and managing information on a construction project that gives architects, engineers, and construction professionals the insight and tools to work more efficiently and effectively throughout the whole project lifecycle.

Civil Aviation Authority (CAA)

The statutory corporation which oversees and regulates all aspects of civil aviation in the United Kingdom.

Ground Control Point (GCP)

A physical marker on the ground that is used to keep a map geographically accurate. The location of a GCP is noted with an RTK (Real Time Kinematic) GPS (or other Global Navigation Satellite System) coordinate. This is a very accurate coordinate and allows the whole map to be aligned properly with the surrounding geographical area. Essentially, it makes sure that one point of the image is aligned with the precise GPS coordinate on the earth. This is very important if the map is going to be compared to older map data, overlaid over other remote imagery, or relied upon for survey-accurate results.

Green Leaf Index (GLI)

An indication of vegetative growth and development derived from RGB camera data.  It adjusts for the greenness and yellowness of a crop and is applicable to all growth stages.

Global Positioning System (GPS)

A “constellation” of approximately 30 satellites that orbit the Earth and make it possible for people with ground receivers to pinpoint their geographic location.

Infrared (IR)

Electromagnetic radiation or light with shorter wavelength (higher frequency) than near infrared.

Light Detection And Ranging (LIDAR)

A surveying method that measures distance to a target by illuminating it with pulsed laser light and detecting the reflections with a sensor.

Normalised Difference Vegetation Index (NVDI)

Quantifies the health of crops by measuring the difference between reflected Near IR and red light.  The chlorophyll in healthy crops results in more Near IR being reflected compared to other wavelengths but far less red light.  Crops that are stressed or dead reflect more red light but less Near IR.  NVDI is applicable to all growth stages.

Near IR (NIR)

A spectrum of light (electromagnetic radiation) that is slightly above the wavelength of visible light. The amount of NIR light reflected off a plant can be a good indicator of its health.


An aerial image corrected for topographic relief, camera tilt, and lens distortions such that the scale of the image is uniform throughout.

Permission for Commercial Operations (PfCO)

Approval bestowed by the CAA to enable a suitably qualified individual or company employee to operate drones for reward or gain.


The science of obtaining measurements from photographs, usually taken from the air.

Point Cloud

A collection of points or coordinates on an object’s surface and can be used to create a 3D model of the object. Point Clouds are often derived from photogrammetric and LIDAR data.

Relative Accuracy

Refers to how accurate a point on a map is to other points on the same map. This means that if two points on a map are X cm apart on the map, they should be X cm apart in the real world.


The level of detail on a map.  Resolution is often measured in cm/pixel, which means that for every pixel X amount of cm will be represented on the map.

Red Green Blue (RGB) Camera

The traditional type of camera. It takes a sample of Red, Green, and Blue light to create an image.

Real Time Kinematic (RTK)

A satellite navigation technique used to enhance the precision of data derived from satellite based positioning systems such as GPS. Essentially, the RTK receiver analyses the GPS radio signal together with data from an associated reference station to derive real-time corrections to its position resulting in centimetre level accuracy.

Visible Atmospherically Resistant Index (VARI)

Used to estimate the fraction of vegetation in an area based on data from an RGB camera.  It exhibits low sensitivity to atmospheric effects and can be used to analyse crops in all growth stages.

Visual NDVI

An indicator of green crop canopies derived from RGB camera data. It can be used to analyse crops in all growth stages.

Visual Line Of Sight (VLOS)

The CAA regulates that a drone must remain within unaided eyesight of the person flying it, except for sunglasses or prescription lenses (spectacles).

Unmanned Aerial Vehicle (UAV)

An aircraft piloted by remote control or on-board computers.  More commonly known as a drone but also referred to as a Remotely Piloted Aircraft System (RPAS), Small Unmanned Aircraft (SUA), Small Unmanned Surveillance Aircraft (SUSA) and Unmanned Aircraft System (UAS).