hexmapApp (Hexagonal Watershed Explorer)

Interactively identify USGS HUC12 subwatershed boundaries using Leaflet, isolate geographic landmass features (e.g., Isle Royale), and overlay spatial hexagonal substrate networks.
Author

Brian S. Yandell

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The hexmapApp() application provides an interactive interface for discovering USGS subwatersheds, isolating specific geographic features (such as island landmasses), and projecting spatial hexagonal substrate networks for quantitative population ethology simulations.

Interactive Application Usage

You can launch the interactive application natively in R:

library(ewing)

# Launch interactive Shiny app
hexmapApp()

[!NOTE] Live Deployment: The interactive application requires dynamic spatial intersection libraries (sf) and live USGS / OpenStreetMap API access. It is deployed live on Posit Connect (HexMap).

Workflow Example: Isle Royale Watershed Projection

Below is an example showing how get_watershed() retrieves the USGS HUC12 subwatershed boundary (041800000101), clips it to the Isle Royale landmass using OpenStreetMap nominatim geometry (when osmdata is available), and overlays a spatial hexagonal grid (add_watershed_hex_overlay).

library(ewing)
library(ggplot2)

# Check if osmdata is installed for feature boundary restriction
feat_name <- if (requireNamespace("osmdata", quietly = TRUE)) "Isle Royale" else NULL

# 1. Fetch HUC12 boundary (optionally restricted to Isle Royale island landmass)
huc_info <- get_watershed("041800000101", feature_name = feat_name)

# 2. Construct spatial hexagonal overlay mesh (diameter = 0.01 degrees)
hex_obj <- add_watershed_hex_overlay(huc_info, hex_diameter = 0.01)

# 3. Visualize using autoplot
ggplot2::autoplot(hex_obj)

Technical Features

  1. Leaflet Spatial Discovery: Click any location on North America or search landmark strings to reverse-geocode coordinates into USGS HUC12 subwatershed IDs (get_huc_from_point).
  2. Feature Isolation: Clip large HUC boundaries covering open water to target landmasses (e.g. Isle Royale) using osmdata::getbb().
  3. Hexagonal Mesh Scaling: Parameterize cell extent diameter to scale spatial resolution dynamically.