1d Water Level Interpolation along the Rivers Elbe and Rhine R package hyd1d version 0.5.4 An S4 class and several functions which utilize internally stored datasets and gauging data enable 1d water level interpolation. The S4 class (WaterLevelDataFrame) structures the computation and visualisation of 1d water level information along the German federal waterways Elbe and Rhine. 'hyd1d' delivers 1d water level data - extracted from the 'FLYS' database - and validated gauging data - extracted from the hydrological database 'WISKI7' - package-internally. For computations near real time gauging data are queried externally from the 'PEGELONLINE REST API' <https://pegelonline.wsv.de/webservice/dokuRestapi>. Software Depends: R (>= 4.1.0) Imports: methods, utils, Rdpack, httr2, curl Suggests: DBI (>= 0.4-9), RPostgreSQL (>= 0.6-1), testthat, knitr, rmarkdown, stringr, devtools, pkgdown, roxygen2, revealjs, shiny, shiny.i18n, shinyTime, lubridate, usethis, yaml, desc Arnd Weber <arnd.weber@bafg.de> Comprehensive R Archive Network (CRAN) Arnd Weber [aut, cre] (ORCID: <https://orcid.org/0000-0002-5973-2770>), Marcus Hatz [aut], Wolfgang Stürmer [ctb], Wilfried Wiechmann [ctb], Benjamin Eberhardt [ctb] GPL (>= 2) 2025-12-03 application/tgz https://CRAN.R-project.org/package=hyd1d doi:10.32614/CRAN.package.hyd1d