Shiny Contest Submission: Viscover - Visualize soil and crop data and their overlay


This is a shiny app tool designed for interacting with Cropland Data Layer (CDL) and Soil Data Layer (SDL). CDL is geo-referenced crop-specific land cover data, created annually for the contiguous United States since 2008. SDL contains tabular and spatial soil information available for the United States and the Territories. Unlike the official tools on the USDA website, this app provides a user-friendly interface to interact with public Federal data from different sources and allows users to make cross-reference through the overlay operation. Besides leaflet and plotly, this app mainly relies on my tiny R package viscover on GitHub to query these two public databases with Web Map Service and Web Geo-processing Service. This app can be adapted to visualize other various Federal data where web services are supported and nicely documented, such as Normalized Difference Vegetation Index (NDVI), Vegetation Condition Index (VCI), National Land Cover Data (NLCD), etc.



Key Technical Details

  • leaflet::addWMSTile with customized url and correctly specified CRS allows SDL and CDL images to be shown on the map accurately and instantly.
  • addAwesomeMarker with customized HTML gives the nicely formatted hover labels.
  • Markers triggered by map-click are labeled with Sys.time(), therefore markers can be tracked and removed at another map-click at the same locations.

For your information, the viscover package can be found at

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