Multiple Angle Observations Would Benefit Visible Band Remote Sensing Using Night Lights

Abstract

The spatial and angular emission patterns of artificial and natural light emitted, scattered, and reflected from the Earth at night are far more complex than those for scattered and reflected solar radiation during daytime. In this commentary, we use examples to show that there is additional information contained in the angular distribution of emitted light. We argue that this information could be used to improve existing remote sensing retrievals based on night lights, and in some cases could make entirely new remote sensing analyses possible. This work will be challenging, so we hope this article will encourage researchers and funding agencies to pursue further study of how multi-angle views can be analyzed or acquired.Plain Language Summary When satellites take images of Earth, they usually do so from directly above (or as close to it as is reasonably possible). In this comment, we show that for studies that use imagery of Earth at night, it may be beneficial to take several images of the same area at different angles within a short period of time. For example, different types of lights shine in different directions (street lights usually shine down, while video advertisements shine sideways), and tall buildings can block the view of a street from some viewing angles. Additionally, since views from different directions pass through different amounts of air, imagery at multiple angles could be used to obtain information about Earth's atmosphere, and measure artificial and natural night sky brightness. The main point of the paper is to encourage researchers, funding agencies, and KYBA ET AL.

X,Y, and Z: A bird's eye view on light pollution

“…Measuring light pollution remains a complex challenge, which can be seen from a number of recent publications (Kolláth et al, 2021 ; Kyba et al, 2022 ; Levin et al, 2019 ; Masana et al, 2021 ). For example, investigating the impact of ecological light pollution on the behavior of living organisms is challenging since ambient lighting conditions can change rapidly and vary considerably between places (Cinzano & Falchi, 2012 ; Jechow et al, 2017 ; Vandersteen et al, 2020 ).…”

“…For example, investigating the impact of ecological light pollution on the behavior of living organisms is challenging since ambient lighting conditions can change rapidly and vary considerably between places (Cinzano & Falchi, 2012 ; Jechow et al, 2017 ; Vandersteen et al, 2020 ). Therefore, it is extremely challenging that the resolution in time and place is not a strength of today's satellite‐based remote sensing systems (Kolláth et al, 2021 ; Kyba et al, 2022 ; Levin et al, 2019 ; Vandersteen et al, 2020 ). Additionally, it is problematic that today's systems cannot detect light visible to birds, insects, and bats (Briscoe & Chittka, 2001 ; Cuthill et al, 2000 ; de Miguel et al, 2021 ; Winter et al, 2003 ).…”

“…The multi‐angle measurements of ALAN are essential to improve existing remote sensing retrievals and may even allow for entirely new remote sensing analyses. However, due to the laboriousness of today's multi‐angle measurement methods, they are still rare (Kyba et al, 2022 ; Walczak et al, 2021 ), and new methods to reduce the effort of acquiring the data are desirable.…”

Spatiotemporal Evolution and Correlation Analysis of Carbon Emissions in the Nine Provinces along the Yellow River since the 21st Century Using Nighttime Light Data

“…Nighttime light remote sensing is an optical remote sensing technology that detects and obtains information on nighttime lights, providing a quick, accurate, and objective view of the surface and human activities [14][15][16]. Unlike daytime remote sensing, nighttime light remote sensing can reveal information that is not visible during the day [17,18]. Since most of the stable light at night comes from artificial sources in urban areas, remote sensing images of nighttime lights can more intuitively reflect differences in human activity at night [19][20][21][22].…”

Citizen scientists report global rapid reductions in the visibility of stars from 2011 to 2022

“…The contributions to ground-observed skyglow and satellite-observed surface radiance depend on the lighting type. Most satellite radiometers have little to no sensitivity to light emitted toward the horizon (e.g., from a window or self-luminous sign) ( 30 ). However, light propagating toward the horizon is the largest contributor to skyglow because of its longer path length (by an order of magnitude) from ground to space at such angles.…”