Timelines are a very effective way of visualizing data inventory. They lead to the improvement of both data curation and exploration. Here, we present timelines for archived ocean-bottom pressure data and coastal tide gauge data at the National Centers for Environmental Information (NCEI). Metadata about the inventories are expressed in Javascript Object Notation (JSON) format and visualized on a timeline through an open-source Javascript library (VisJS). Through these timelines, gaps in coverage immediately become apparent. Within the first two months of the DART timeline going live, NOAA's National Data Buoy Center, our primary data provider, used this inventory visualization to identify and submit for archive 17 at-risk data packages from the backlog of data collection that were not previously submitted for archive. Given the high cost of collecting these data, this represents a significant return on investment. Dates and heights of reported tsunami waves, as recorded in NCEI's historical tsunami hazards database, have been superposed on this timeline to draw attention to events of interest. Broader use of this approach to time-series exploration would benefit from the caching or predetermination of data inventories at different gap thresholds and providing these inventories using web services.

See https://www.ngdc.noaa.gov/hazard/dart, https://www.ngdc.noaa.gov/hazard/bpr, and https://www.ngdc.noaa.gov/hazard/tide.