extract_coords: Extract coordinates

In crstools: Tools to Work with Projections

Extract coordinates

Description

Extract coordinates from a georeferenced image.

Usage

extract_coords(georef_image, coords_df = NULL, col = "red")

Arguments

georef_image	A spatraster object representing the georeferenced image.
coords_df	An optional dataframe containing the coordinates of points previously extracted from the image. Default is NULL.
col	The colour of the points to be plotted on the image. Default is "red".

Value

A dataframe with ID and coordinates of the points extracted from the image.

Examples

# Load required packages
library(terra)
# Georeference the image using the created GCPs
# get the gcp coordinates
gcp_europe_coords <-
readRDS(system.file("vignettes/img/europe_gcp_georef_v2.RDS",
package = "crstools"))
# get the path to the image
img_path <- system.file("extdata/europe_map.jpeg", package = "crstools")
georef_path <-
georeference_img(image_obj = img_path,
gcp = gcp_europe_coords,
output_path = file.path(tempdir(), "europe_map_georef"))
# georeference the image using the GCPs
map_warp <- rast(georef_path)
# get the coordinates of the points
coords_df <- extract_coords(map_warp)
# if needed, extract additional points by supplying the coords_df argument
# and re run the function
coords_df <- extract_coords(map_warp, coords_df)
# dataframe with ID and coordinates of the points extracted from the image.
print(coords_df)

crstools documentation built on March 19, 2026, 5:08 p.m.