DATASET_CARD.md

Dataset Card: Heat-Assisted Detection and Ranging (HADAR) Inputs

Overview

This bundle supports ground-based long-wave infrared (LWIR) hyperspectral imaging for heat-assisted detection and ranging. It combines five scenes from the DARPA IH Dataset with a shared U.S. Standard Atmosphere (USSA) spectral pair: horizontal-path attenuation coefficients and a ten-angle downwelling-radiance basis.

The atmospheric products are a frozen copy of the data/ directory from Ozone-Cues (LWIR absorption-based ranging). All five IH captures are daylight, near-surface scenes. For clear-sky conditions with similar air temperatures, recent work on this problem finds that site-to-site differences in downwelling spectral features are small compared with other inversion errors, so the five cubes share one USSA atmosphere rather than a per-scene sounding.

The ENVI cubes are too large for GitHub. The image build fetches this same layout from the frozen Hugging Face dataset dccc2025/tmp_dataset_hadar and checks SHA256. That fetch is pinned to a commit (not a moving main branch) and is not a live scrape of Kitware.

Directory Layout

inputs/
├── DATASET_CARD.md
├── attenuation.npz
├── I_downwelling_res.npz
└── original_datasets/
    ├── IHTest_202104_Path26_Step2_LWHSI1_collect0_DistStA.{bsq,hdr}
    ├── IHTest_202104_Path27_Step25_LWHSI1_collect0_DistStA.{bsq,hdr}
    ├── IHTest_202204_Path2_Step1_LWHSI2_DistStA.{bsq,hdr}
    ├── IHTest_202204_Path13_Step9_LWHSI2_DistStA.{bsq,hdr}
    └── IHTest_202204_Path13_Step13_LWHSI2_DistStA.{bsq,hdr}

1. Hyperspectral Scenes (original_datasets/)

Five ENVI-format LWIR hyperspectral cubes (.bsq + .hdr) from the DARPA IH Dataset. Each pair is a band-sequential cube plus acquisition metadata. Headers record wavelength (µm) and a near-surface air temperature (kelvin). They do not record a radiance scale factor.

Scene stem	Acquisition time (UTC)	Lines	Samples	Bands
IHTest_202104_Path26_Step2_LWHSI1_collect0_DistStA	2021-04-20T23:13:02	260	1600	256
IHTest_202104_Path27_Step25_LWHSI1_collect0_DistStA	2021-04-21T03:24:47	260	1600	256
IHTest_202204_Path2_Step1_LWHSI2_DistStA	2022-04-20T21:14:29	480	1500	250
IHTest_202204_Path13_Step9_LWHSI2_DistStA	2022-04-22T23:00:35	480	1500	250
IHTest_202204_Path13_Step13_LWHSI2_DistStA	2022-04-22T23:09:03	480	1500	250

• Format: ENVI BSQ, 32-bit float (data type = 4).
• Wavelengths: Stored in each .hdr file; units are micrometers (µm).
• Distribution: Distribution Statement A (see scene headers).

Cube radiance units

The .bsq arrays are not already in (\mathrm{W,m^{-2},sr^{-1},\mu m^{-1}}). They are stored a factor of (10^{2}) high relative to physical spectral radiance. Convert with

[ L_{\lambda};[\mathrm{W,m^{-2},sr^{-1},\mu m^{-1}}] = 10^{-2},L_{\mathrm{bsq}}. ]

Use this scaled (L_{\lambda}) in any comparison to Planck (B_\lambda(T)) or to the bundled downwelling basis (which is already in physical units). Do not treat header temperature as the surface temperature map; it is local air temperature.

Source Citation

@InProceedings{Yellin_2024_WACV,
    author    = {Yellin, Florence and McCloskey, Scott and Hill, Cole and Smith, Eric and Clipp, Brian},
    title     = {Concurrent Band Selection and Traversability Estimation from Long-Wave Hyperspectral Imagery in Off-Road Settings},
    booktitle = {Proceedings of the IEEE/CVF Winter Conference on Applications of Computer Vision (WACV)},
    month     = {January},
    year      = {2024}
}

Dataset homepage: https://www.kitware.com/ihdataset/

2. Spectral Attenuation (attenuation.npz)

Frozen USSA horizontal-path spectral attenuation, copied from the Ozone-Cues data/ snapshot above. Not recomputed per scene.

Key	Shape	Description
attenuation	(256, 1)	Spectral attenuation coefficient α, in dB m⁻¹
lambda	(1, 256)	Wavelength grid paired with attenuation, in µm

Value range (α): approximately 2.8×10⁻⁴ to 1.4×10⁻² dB m⁻¹ over 7.98–13.05 µm.

Load example:

import numpy as np

data = np.load("attenuation.npz")
alpha = data["attenuation"]   # (256, 1), dB/m
lam_att = data["lambda"]      # (1, 256), µm

3. Downwelling-Radiance Basis (I_downwelling_res.npz)

Ten resampled USSA downwelling spectral radiance profiles, one per zenith angle, from the same Ozone-Cues data/ snapshot. These columns are a fixed angular basis for reflected hemispherical downwelling. They are already in physical radiance units.

Key	Shape	Description
lambda	(1, 256)	Wavelength grid, in µm (approximately 8.10–13.17 µm)
downwelling_res	(256, 10)	Downwelling spectral radiance at each angle, in W m⁻² sr⁻¹ µm⁻¹

Zenith angles (column order, degrees):

0, 30, 60, 70, 80, 82, 84, 86, 88, 89

Column k of downwelling_res corresponds to zenith angle k in the list above.

Load example:

import numpy as np

data = np.load("I_downwelling_res.npz")
lam = data["lambda"]                    # (1, 256), µm
I_down = data["downwelling_res"]        # (256, 10), W·m⁻²·sr⁻¹·µm⁻¹

Units and Conventions

Quantity	Symbol / key	Units
Wavelength	lambda	µm
Attenuation coefficient	attenuation (α)	dB m⁻¹
Downwelling spectral radiance	downwelling_res	W m⁻² sr⁻¹ µm⁻¹
Hyperspectral cube	ENVI .bsq	stored (10^{2}) high; (L=10^{-2}L_{\mathrm{bsq}}) in W m⁻² sr⁻¹ µm⁻¹
Header temperature	air temperature	K

Notes for Use

1. Wavelength alignment. LWHSI1 cubes have 256 bands starting near 8.06 µm. LWHSI2 cubes have 250 bands starting near 6.84 µm. The downwelling lambda grid is a 256-channel LWIR window and does not automatically match every scene. Interpolate or band-select every spectral product onto the scene wavelength grid before combining them.
2. Separate attenuation grid. attenuation.npz has its own lambda axis, offset from the downwelling grid. Resample attenuation onto the scene grid before using (\tau(d)=10^{-\alpha d/10}).
3. Shared atmosphere. One USSA attenuation cube and one ten-angle downwelling basis are used for all five scenes. This is a documented approximation for clear-sky, similar-temperature collections, not a claim that the real soundings were identical.
4. Downwelling basis. Treat the ten columns of downwelling_res as a fixed, ordered angular basis; do not permute them. They are not the delivered single-band texture map X.
5. Scene selection. IHTest_202104_Path27_Step25_LWHSI1_collect0_DistStA replaces the previous 202108 Path9 cube. Path9 had too little thermal-texture and range contrast (nearly flat X and d) to invert stably. Path27 is the same LWHSI1 camera family (260×1600×256) with more usable geometric texture and ranging contrast. This Path27 header does not include an air temperature field; use the solver fallback (default 290 K) unless you set path temperature another way.