Quantification of Urban Thermal Infrared Anisotropy at the TRISHNA Scale (60 m) from Airborne Measurements
Abstract
The upcoming TRISHNA satellite mission will provide land surface temperature measurements at unprecedented spatial (60 m) and temporal (2-3 days) resolutions, crucial for the study of urban climate. However, its wide scan (±34°) introduces challenges due to directional anisotropy in the brightness temperature, particularly in complex 3D urban landscapes. While several studies have highlighted the strong impact of directional effects on thermal infrared (TIR) measurements over urban areas at city, kilometric and canyon scales, none have investigated these effects at TRISHNA's spatial resolution and angular configuration. This study utilises airborne TIR data to quantify the directional effects at the TRISHNA pixel scale across three urban morphologies: a central square, a dense urban area, and a residential neighbourhood. These effects are examined at different times of the day and different seasons. The analyses highlighted important anisotropy in brightness temperature within the TRISHNA viewing angle range, over the three urban landscapes and for all daytime acquisitions. The strongest effects, up to 4.4 K, are observed in summer mornings and along the solar plane with a strong dependency on observation angle, illumination and surface geometry. Despite limitations in airborne data availability, the results indicate that dense urban morphology exhibits homogeneous directional behaviour whereas vegetation cover seems to mitigate anisotropy. As a preliminary evaluation, these findings underline the need to account for angular dependencies in TRISHNA land surface temperature products to maintain accuracy, especially for high-frequency revisits involving multi-angle observations.
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BibTeX
@misc{dehaene2026quantification,
title = {{Quantification of Urban Thermal Infrared Anisotropy at the TRISHNA Scale (60 m) from Airborne Measurements}},
author = {Q Dehaene and L Roupioz and M Irvine and F Nerry and X Briottet},
howpublished = {HAL},
year = {2026},
month = sep,
url = {https://hal.science/hal-05737039v1},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Quantification of Urban Thermal Infrared Anisotropy at the TRISHNA Scale (60 m) from Airborne Measurements
AU - Q Dehaene
AU - L Roupioz
AU - M Irvine
AU - F Nerry
AU - X Briottet
PY - 2026
DA - 2026/09/03
PB - HAL
UR - https://hal.science/hal-05737039v1
AB - The upcoming TRISHNA satellite mission will provide land surface temperature measurements at unprecedented spatial (60 m) and temporal (2-3 days) resolutions, crucial for the study of urban climate. However, its wide scan (±34°) introduces challenges due to directional anisotropy in the brightness temperature, particularly in complex 3D urban landscapes. While several studies have highlighted the strong impact of directional effects on thermal infrared (TIR) measurements over urban areas at city, kilometric and canyon scales, none have investigated these effects at TRISHNA's spatial resolution and angular configuration. This study utilises airborne TIR data to quantify the directional effects at the TRISHNA pixel scale across three urban morphologies: a central square, a dense urban area, and a residential neighbourhood. These effects are examined at different times of the day and different seasons. The analyses highlighted important anisotropy in brightness temperature within the TRISHNA viewing angle range, over the three urban landscapes and for all daytime acquisitions. The strongest effects, up to 4.4 K, are observed in summer mornings and along the solar plane with a strong dependency on observation angle, illumination and surface geometry. Despite limitations in airborne data availability, the results indicate that dense urban morphology exhibits homogeneous directional behaviour whereas vegetation cover seems to mitigate anisotropy. As a preliminary evaluation, these findings underline the need to account for angular dependencies in TRISHNA land surface temperature products to maintain accuracy, especially for high-frequency revisits involving multi-angle observations.
ER -