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rgpsgisr-sf

simple feature - create new points with certain properties

I've a simple features with a simple point, arround this point I like to create 6 new points equal distributed and 100 meter away from the orginal point. Is this easily solvable in R (sf) and do you have perhaps an example how I could implement something like this?

Solution

  • Start by buffering the point by 100 meters, cast it to a linestring, and then sample the buffered linestring:

    library(sf)
#> Linking to GEOS 3.8.0, GDAL 3.0.4, PROJ 6.3.1; sf_use_s2() is TRUE
library(tidyverse)


set.seed(41)
point <- st_sfc(st_point(c(0, 51.5))) %>% st_set_crs(4326) # a point around London

buffer <- st_buffer(point, dist = 100) %>% 
  st_cast('LINESTRING')

six_points <- st_sample(buffer, size = 6, type = 'regular')
#> although coordinates are longitude/latitude, st_sample assumes that they are
#> planar

#distances:
six_points %>% st_as_sf() %>% st_cast('POINT') %>% st_distance(point)
#> Units: [m]
#>          [,1]
#> [1,] 100.5366
#> [2,] 100.2739
#> [3,] 100.7187
#> [4,] 100.5599
#> [5,] 100.2410
#> [6,] 100.6761

    Pretty close. Choosing a better crs would help if you need cm accuracy.

    
ggplot() +
  geom_sf(data = point, col = 'red') + 
  geom_sf(data = buffer) +
  geom_sf(data = six_points, color = 'turquoise', size = 4) +
  theme_void()

    On a map:

    library(mapview)
mapview(point) +
  buffer +
  six_points

    library(mapview) mapview(point) + buffer + six_points

    Created on 2023-03-31 by the reprex package (v2.0.1)