Detection · Recognition · Identification range for any electro-optical or thermal sensor

DRI Range Calculator

Describe a detector, a lens and a target; the tool returns the detection, recognition and identification range, and says which limit sets each one. Nothing in it is tied to a particular product.

This tool needs JavaScript to change the settings. The table below is the result for the default configuration.

Sensor

aWhat kind of sensor?

bDetector

Array width (px)Array height (px)

Pixel pitch (µm)

Fill from a common formatFill from a common pitch

cLens focal length

Add a focal length (mm)

Quick add

dOptional detail

f-numberNETD (mK)

Targets

Custom

Name

Height (m)Width (m)

Task and conditions

Probability of success

Sensor height above ground

Or type a height (m)

Atmosphere

Apply horizon limitApply atmospheric limitApply diffraction limit

Model settings

These change how the model works rather than what you are measuring. The defaults are the usual conventions; every one of them is stated on the result so a reader knows what they are looking at.

Criteria convention

Critical dimension

Horizon refraction model

d [km] = k (√h_sensor + √h_target). 3.57 is the true geometric horizon; 3.86 adds the standard optical and infrared refraction (k ≈ 7/6) and is the right default here; 4.12 is the 4/3-earth radar convention and is optimistic for an imaging sensor.

ΔT₀ (K)Threshold ×NETD

Contrast thresholdAirlight Lair / Lbg

ΔT₀ and the ×NETD threshold drive thermal bands; the contrast threshold and airlight ratio drive SWIR, NIR, visible and intensified bands. Both thresholds are scaled by the task’s cycle count as a first-order stand-in for MRTD and MRC rising with spatial frequency — replace them with measured curves before using this for anything contractual.

σ base (km⁻¹)σ × for LWIR

σ presets are visible-band extinction coefficients. Published field data puts LWIR range in category-II fog at roughly four times MWIR, which would correspond to an LWIR multiplier well below 1 in the fog presets. The default is left at 1.00 because band-resolved coefficients need MODTRAN-class data; set it deliberately rather than inheriting a guess.

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Full matrix

Sensor	Band	f mm	Resolution cyc/mrad	Detect km	Recognise km	Identify km	Limited by
NATO standard target · 2,3 × 2,3 m
LWIR 640×512 · 12 µm	LWIR	150	6,25	11,3	4,79	2,4	Horizon
Human · 1,8 × 0,5 m
LWIR 640×512 · 12 µm	LWIR	150	6,25	7,91	1,98	0,988	Sensor

Resolution is given in cycles per milliradian because that is the one quantity a sampled array and an intensifier tube can be compared on — for an array it is f / (2 × pitch), for a tube it is f × lp/mm. Ranges use 1.5 / 6 / 12 pixels — 0.75 / 3 / 6 cycles at 50% probability.

Full matrix

Optics summary

The same answer under other conventions

All calculations run in your browser. Nothing is sent to Inventra.

This tool uses a geometric Johnson-criteria model with an NVESD target transfer probability function, optional Beer–Lambert atmospheric attenuation, a diffraction ceiling and a refracted-horizon limit. It is not TRM4, NV-IPM or STANAG 4347 — those are measurement-based models and are licensed or export-controlled. Real performance depends on target contrast, background clutter, scene temperature, operator training and the atmosphere on the day.

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