# Ozone Cues Mitigate Reflected Downwelling Radiance in LWIR Absorption-Based Ranging Source: [Ozone Cues Mitigate Reflected Downwelling Radiance in LWIR Absorption-Based Ranging]() Collection index: [llms.txt]() Data updated: 2026-03-04T05:00:05.078Z Authors: Unay Dorken Gallastegi, Wentao Shangguan, Vaibhav Choudhary, Akshay Agarwal, Hoover Rueda-Chac\\'on, Martin J. Stevens, Vivek K Goyal Published: 2026-02-27T19:46:17.000Z ## Abstract Passive long-wave infrared (LWIR) absorption-based ranging relies on atmospheric absorption to estimate distances to objects from their emitted thermal radiation. First demonstrated decades ago for objects much hotter than the air and recently extended to scenes with low temperature variations, this ranging has depended on reflected radiance being negligible. Downwelling radiance is especially problematic, sometimes causing large inaccuracies. In two new ranging methods, we use characteristic features from ozone absorption to estimate the contribution of reflected downwelling radiance. The quadspectral method gives a simple closed-form range estimate from four narrowband measurements, two at a water vapor absorption line and two at an ozone absorption line. The hyperspectral method uses a broader spectral range to improve accuracy while also providing estimates of temperature, emissivity profiles, and contributions of downwelling from a collection of zenith angles. Experimental results demonstrate improved ranging accuracy, in one case reducing error from over 100 m when reflected light is not modeled to 6.8 m with the quadspectral method and 1.2 m with the hyperspectral method. ## Recorded benchmark results A research result applies to its stated dataset, split, metric and evaluation configuration. Compare like-for-like settings, preserve the metric's unit and direction, and distinguish paper-reported results from independent reproduction. The best result recorded here is not a claim of exhaustive, current global coverage. - [Passive Ranging on DARPA Invisible Headlights Foreground tree (20 x 40 representative patch)](): Passive Ranging; DARPA Invisible Headlights Foreground tree (20 x 40 representative patch); Mean Distance (m): 83.67. - [Passive Ranging on DARPA Invisible Headlights Grass (20 x 40 representative patch)](): Passive Ranging; DARPA Invisible Headlights Grass (20 x 40 representative patch); Mean Distance (m): 39.73. - [Passive Ranging on DARPA Invisible Headlights Background forest patch (20 x 40 representative patch)](): Passive Ranging; DARPA Invisible Headlights Background forest patch (20 x 40 representative patch); Mean Distance: 194.52. ## Original sources and implementation [Original paper]() [PDF]()