EO/IR Payload Glossary: 25 Terms Every Buyer Should Know

Payload datasheets compress engineering into jargon. Here are the 25 terms that actually decide purchasing decisions, each defined in one breath.

• 25Terms that matter
• 4 groupsSensing, optics, control, workflow
• 3That filter datasheets fastest
• 1 breathPer definition

Sensing

EO — electro-optical, the visible-light channel. IR / LWIR — infrared, the 8–14 µm thermal band; why that band. Microbolometer — the uncooled thermal sensor type used on essentially all UAV payloads.

NETD — noise equivalent temperature difference, the smallest temperature difference the sensor resolves; lower is better, and the f-number beside it matters as much as the number. Pixel pitch — sensor element size; smaller pitch enables lighter optics, which is the 12 µm story.

Radiometric — calibrated per-pixel temperature measurement, as opposed to relative contrast. Starlight sensor — ultra-low-lux visible imaging that amplifies existing light. NIR illumination — an invisible near-infrared floodlight, typically 850 nm, for zero-light identification.

Cooled vs uncooled — cooled photon detectors reach finer sensitivity at the cost of mass, power and a cooldown wait; why drones chose microbolometers.

Optics and Range

Focal length — sets field of view and therefore range; the wide-versus-narrow trade. IFOV — instantaneous field of view, the angular size of one pixel, and the real resolution-at-distance metric.

Optical zoom — changes focal length, adds real detail. Digital zoom — crops and enlarges existing pixels, adds none. Hybrid zoom — the product of the two, which is legitimate shorthand and easy to misread.

DRI — detection, recognition and identification range thresholds, each needing roughly double the pixels of the previous; explained, including the two competing standards. LRF — laser rangefinder, for target distance and geolocation.

Germanium — the material thermal lenses are made from, since glass is opaque at 8–14 µm. f-number — aperture speed; a faster lens gathers more energy and NETD figures are often quoted at f/1.0.

Stabilisation and Control

3-axis gimbal — roll, pitch and yaw mechanical stabilisation; what each axis contributes. Pointing accuracy — how precisely the gimbal holds a command; ±0.01° class matters at zoom, and here is why in centimetres.

Drift — slow pointing wander over time, distinct from jitter. Jitter — high-frequency residual shake. Controllable range — how far each axis can be commanded, which decides whether the payload can point where you need it.

S.BUS / PWM / CAN / serial — the four common control interfaces, compared here. MAVLink gimbal protocol — the autopilot-standard pointing control, covered in ArduPilot and PX4 integration.

Boresight alignment — the factory calibration that makes a point in the thermal frame the same point in the visible frame.

Imaging Workflow

Palette — thermal colour mapping; white hot, black hot, ironbow compared. Isotherm — alarm colouring above or below set temperatures, automating the find. PiP — picture-in-picture thermal and visible display.

Gain modes — high gain gives fine resolution over a narrow temperature range; low gain gives a wide range for fire work. ONVIF — the network video standard for VMS integration; the guide. Glass-to-glass latency — sensor-to-screen delay, with budgets by mission.

AI tracking — onboard detection and click-to-track lock; how it actually works. Emissivity — how efficiently a surface radiates, and the largest source of wrong readings.

Term	One-line definition	Why it decides a purchase
NETD	Smallest resolvable temperature difference	Governs low-contrast detection
IFOV	Angular size of one pixel	The real resolution-at-distance figure
Optical zoom	Magnification that adds detail	The only zoom number that matters
Radiometric	Calibrated per-pixel temperature	Cannot be added later
Pointing accuracy	How precisely the gimbal holds aim	Caps usable zoom
DRI	Detection/recognition/identification ranges	Sets mission feasibility
Pixel pitch	Sensor element size	Indicates core generation and optics size

Related reading

• From NETD to DRI
• How Uncooled VOx Microbolometers Work
• How to Read a Thermal Payload Spec Sheet
• What Payload Buyers Should Ignore First
• DRI Ranges Explained
• Thermal Sensitivity (NETD) Explained
• Hybrid Zoom on UAV Cameras
• What ±0.01° Gimbal Accuracy Means at 1,000 Metres
• MV-2P — 640×512 thermal at 130 g
• OP-90A — zoom, thermal and ranging
• OP-125A — flagship EO/IR pod
• Power Line Inspection Drone Payloads

FAQ

Which three terms filter datasheets fastest?

Optical zoom factor, NETD with its f-number, and pointing accuracy. The first separates real reach from digital multiplication, the second tells you whether low-contrast findings will survive the noise floor under a stated aperture, and the third tells you whether high-magnification imagery will be usable at all. Two payloads that match on all three are genuinely comparable; two that match on headline resolution alone are not.

What is the difference between IFOV and resolution?

Resolution is the pixel count of the array; IFOV is the angular size that one pixel subtends, which depends on both pixel pitch and focal length. IFOV is the more useful figure because it directly determines how many pixels land on a target at a given distance — the quantity that governs detection and identification. Two payloads with the same resolution can have very different IFOV, and therefore very different real-world range.

Which terms describe things that cannot be changed after purchase?

Radiometric calibration, lens focal length on an integrated payload, and the link-specific variant. All three are factory configurations sealed into the unit — radiometry because it depends on per-core calibration data, the lens because it is built into a boresight-aligned assembly, and the variant because the video and control interfacing is hardware-level. Everything else can be adapted, replaced or worked around.

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