SpectralIndices.jl: Streamlining spectral indices access and computation for Earth system research

Abstract. Remote sensing is an essential technology in environmental science to study Earth surface processes. In optical remote sensing, spectral indices (SI) are widely used to quantify the properties of specific surface characteristics. SI mathematically combine reflectance values measured at different wavelengths. To gain an overview and access to such indices, comprehensive catalogs have been published and implemented in various programming languages. However, there is no Julia-based tool available for efficiently managing and using these indices. Here we introduce SpectralIndices.jl, a Julia package designed to retrieve and compute SI. Built on the Awesome Spectral Indices (ASI) catalog, our package enables rapid computation of SI using native functions. The multiple dispatch capability of Julia optimizes data handling across various storage types, ensuring quick load times. While primarily based on the ASI collection, SpectralIndices.jl also accommodates custom-made indices, offering users the flexibility to explore and compare alternative indices. The software is open source and available on github.com/awesome-spectral-indices/SpectralIndices.jl