Coverage Biases in High-Resolution Satellite Imagery

TL;DR

This paper investigates spatial and temporal coverage biases in high-resolution satellite imagery, revealing that geographic, socio-economic, and geopolitical factors influence image availability and revisit frequency worldwide.

Contribution

It provides a comprehensive analysis of coverage biases in satellite imagery, combining orbital data and metadata to reveal inequalities in data distribution across regions.

Findings

Locations near the equator are revisited more frequently.

Less developed areas have fewer available satellite images.

Geopolitical conflicts affect satellite image availability.

Abstract

Satellite imagery is increasingly used to complement traditional data collection approaches such as surveys and censuses across scientific disciplines. However, we ask: Do all places on earth benefit equally from this new wealth of information? In this study, we investigate coverage bias of major satellite constellations that provide optical satellite imagery with a ground sampling distance below 10 meters, evaluating both the future on-demand tasking opportunities as well as the availability of historic images across the globe. Specifically, forward-looking, we estimate how often different places are revisited during a window of 30 days based on the satellites' orbital paths, thus investigating potential coverage biases caused by physical factors. We find that locations farther away from the equator are generally revisited more frequently by the constellations under study. Backward-looking, we show that historic satellite image availability -- based on metadata collected from major satellite imagery providers -- is influenced by socio-economic factors on the ground: less developed, less populated places have less satellite images available. Furthermore, in three small case studies on recent conflict regions in this world, namely Gaza, Sudan and Ukraine, we show that also geopolitical events play an important role in satellite image availability, hinting at underlying business model decisions. These insights lay bare that the digital dividend yielded by satellite imagery is not equally distributed across our planet.