# Absorption-Based, Passive Range Imaging from Hyperspectral Thermal Measurements Source: [Absorption-Based, Passive Range Imaging from Hyperspectral Thermal Measurements]() Collection index: [llms.txt]() Data updated: 2026-03-13T05:00:04.336Z Authors: Unay Dorken Gallastegi, Hoover Rueda-Chacon, Martin J. Stevens, Vivek K Goyal Published: 2023-08-10T18:35:22.000Z ## Abstract Passive hyperspectral longwave infrared measurements are remarkably informative about the surroundings. Remote object material and temperature determine the spectrum of thermal radiance, and range, air temperature, and gas concentrations determine how this spectrum is modified by propagation to the sensor. We introduce a passive range imaging method based on computationally separating these phenomena. Previous methods assume hot and highly emitting objects; ranging is more challenging when objects' temperatures do not deviate greatly from air temperature. Our method jointly estimates range and intrinsic object properties, with explicit consideration of air emission, though reflected light is assumed negligible. Inversion being underdetermined is mitigated by using a parametric model of atmospheric absorption and regularizing for smooth emissivity estimates. To assess where our estimate is likely accurate, we introduce a technique to detect which scene pixels are significantly influenced by reflected downwelling. Monte Carlo simulations demonstrate the importance of regularization, temperature differentials, and availability of many spectral bands. We apply our method to longwave infrared (8--13 $\\mu$m) hyperspectral image data acquired from natural scenes with no active illumination. Range features from 15m to 150m are recovered, with good qualitative match to lidar data for pixels classified as having negligible reflected downwelling. ## 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 Range Imaging on 20 x 40 patches Background forest (experimental)](): Passive Range Imaging; 20 x 40 patches Background forest (experimental); Mean Distance (m): 162.3. - [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): 76. - [Passive Range Imaging on Patches 20 x 40 Grass (experimental)](): Passive Range Imaging; Patches 20 x 40 Grass (experimental); Mean Distance (m): 48.5. - [Passive Range Imaging on 20 x 40 patches Foreground tree (experimental)](): Passive Range Imaging; 20 x 40 patches Foreground tree (experimental); Mean Distance (m): 76. - [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: 162.3. - [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): 48.5. ## Original sources and implementation [Original paper]() [PDF]()