# Background

The recent expansion of echosounder deployment on a wide variety of ocean observing platforms have created unique opportunities for characterizing the spatial and temporal distribution of mid-trophic level animals, such as fish and zooplankton, at a broad range of scales. Data from these echosounders are increasingly recognized for their potential and contributions to marine ecosystem observation, as well as resource assessments and management {cite}`benson_2018,estes_2021,satterthwaite_2021,santora_2021,schwing_2023`.

The importance of storing and openly sharing vast amounts of data gathered by scientific echosounders and similar instruments is widely acknowledged {cite}`wall_2016,haris_sounding_2021`. However, maximizing the utilization of such data requires implementing community data and metadata standards, along with establishing data catalogs for enhancing data discoverability and access {cite}`benson_2018,buck_2019`. Further, a consistent categorization of the various echosounder datasets and derived data products will actively facilitate access and appropriate utilization of this valuable data.

Decades of experience in satellite remote sensing have demonstrated that clear and robust definitions of "data processing levels" directly enable broad and highly productive use of data {cite}`parkinson_earth_2006,robinson_2006,weaver_processing_2014,nasa_data_2021,ramapriyan_2021`. These levels differentiate data products from raw data to more highly processed and transformed data, providing essential context for data interpretation {cite}`hills_2015`. However, there is currently no such community agreement for echosounder data.

We believe that a community agreement for echosounder data processing levels can improve the interoperability and inter-comparability of processed echosounder data products, which will facilitate efficient collaboration and integrative use of the rapidly growing echosounder data archives across research institutions and agencies.

<!-- In this document we present a proposed set of processing levels from raw echosounder data to derived data products. We first review the history and use of data processing levels in the broader environmental monitoring community, particularly from satellite systems. We then describe existing schemes applied to echosounder data, and present the proposed processing levels with rationale of the choices. -->
