GIStoolkit

GIStoolkitis a collection of handy R functions for accomplishing common GIS tasks.

Installation

You can install the development version of GIStoolkit from GitHub with:

remotes::install_github("QAWalker/GIStoolkit")

Load the package into your R session

library(GIStoolkit)

Functions

1. Interactive Point Selection

get_clicked_point() launches an interactive map in your viewer or browser and allowing the user to save the clicked point. You must click the marker icon on the left to add a point.

my_point <- get_clicked_point()

2. Interactive Raster Cropping

click_to_crop(raster_obj, mask = TRUE)allows you to define a study area visually.

The maskparameter determines the output:

• mask = TRUE(Default): Launches a polygon tool. The result is clipped to the exact shape, and pixels outside are set to NA.
• mask = FALSE: Launches an extent tool. The result is cropped to a rectangular bounding box.

r <- terra::rast("my_raster.tif")

# To get a polygon shape:
polygon_crop <- click_to_crop(r, mask = TRUE)

# To crop to a rectangular defined by the extend of the points:
rectangle_crop <- click_to_crop(r, mask = FALSE)

# Save Cropped Results
terra::writeRaster(polygon_crop, filename = "path/to/save/polygon_cropped_raster.tif")

terra::writeRaster(rectangle_crop, filename = "path/to/save/rectangle_cropped_raster.tif")

3. Generate Points Along a Line

generate_line_points(line_sf, distance, crs = 5070) samples evenly spaced points along an sf linestring at a given meter interval, including the start and end of the line.

# read in data created as a path in google earth and saved as a .kml file
# can read a shapefile as well
my_line <- sf::st_read("path/to/file.kml")

# Place a point every 100 meters (default CONUS Albers CRS)
pts <- generate_line_points(my_line, distance = 100)

# define the CRS (using UTM Zone 18N for this example)
pts <- generate_line_points(my_line, distance = 100, crs = 32618)

The returned sf object contains a point_id column (sequence along the line) and a distance_m column (cumulative distance from the start).

4. Get NAVD88 Elevation of Tidal Datums

get_datum_elevation(coords, datum = NULL, region = NULL, unit = "m", progress = TRUE) interacts with the NOAA VDatum API to find the exact NAVD88 elevation where a specific tidal datum occurs at given coordinate locations.

# Prepare your coordinate data frame (supports 'X' and 'Y')
my_locations <- data.frame(
  X = c(-75.211, -75.46803),
  Y = c(36.129, 35.602986)
)

# What is the NAVD88 elevation of MHW?
mhw_elevations <- get_datum_elevation(locations, datum = "MHW")

# What is the NAVD88 elevation of MLLW?
mllw_elevations <- get_datum_elevation(locations, datum = "MLLW")

The function returns a simplified data frame containing the coordinates, the requested tidal datum, the corresponding navd88_elevation, and any vertical uncertainty or error metrics returned by the API.

Can be used in conjunction with get_clicked_point to get the

# get point from interactive map
point <- get_clicked_point()

# get MHHW elevation from point
get_datum_elevation(coords = point, datum = "MHHW", unit = "m")