Calculating distance between coordinates and reference point-CodePudding

I want to calculate the distance between lat1, lon1 and a reference point (52.92343, 5.04127). I want to this for every row in my dataset, so the distance will be calculated with the reference in every row. That means I will create a new column with the distance in km. I can imagine you will have to use some kind of loop function, but so far I have not figured out how to accomplish this. I think I will have to use the packages geodist or geosphere, but unfortunately was not successful. How can I calculate these distances?

structure(list(Day = c("26", "05", "17", "18", "19", "19"), Month = c("07", 
"08", "08", "08", "08", "08"), Year = c("2021", "2021", "2021", 
"2021", "2021", "2021"), Location.Receiver = c("Den Oever Ijsselmeer", 
"Medemblik Ijsselmeer, gemaal", "Den Oever Ijsselmeer", "Den Oever Ijsselmeer", 
"Den Oever Ijsselmeer", "Den Oever Ijsselmeer"), Transmitter = c("A69-1602-59776", 
"A69-1602-59777", "A69-1602-59776", "A69-1602-59776", "A69-1602-59769", 
"A69-1602-59776"), Batch.location = c("Den Oever", "Den Oever", 
"Den Oever", "Den Oever", "Den Oever", "Den Oever"), BatchNr = c(8, 
9, 8, 8, 1, 8), Latitude = c(52.92343, 52.76098, 52.92343, 52.92343, 
52.92343, 52.92343), Longitude = c(5.04127, 5.12172, 5.04127, 
5.04127, 5.04127, 5.04127), Date = structure(c(18834, 18844, 
18856, 18857, 18858, 18858), class = "Date")), row.names = c(1095729L, 
1180267L, 1072657L, 1092667L, 716601L, 1077415L), class = "data.frame")

CodePudding user response：

No need to loop, you can just calculate the distance between entries in an array of coordinates in x and a single point in y using geodist. Just passing in the coordinates as lon/lat explicitly and saving back as a numeric vector to Distance rather than as the original matrix output.

library(geodist)

df$Distance <- as.numeric(geodist(df[,9:8], c(5.04127, 52.92343)))
#> object has no named columns; assuming order is lon then lat

df$Distance
#> [1]     0.00 18843.92     0.00     0.00     0.00     0.00

CodePudding user response：

Please find an alternative solution (cf reprex below) using the sf and units library

Reprex

Code

library(sf)
library(units)

# Convert the df into 'sf' object
df_sf <- df %>% 
  st_as_sf(coords = c("Longitude", "Latitude"), crs = 4326)

# Create the reference 'sf' object
ref_point_sf <- st_point(c(5.04127, 52.92343)) %>% 
  st_coordinates() %>% 
  as.data.frame() %>% 
  st_as_sf(coords = c("X", "Y"), crs = 4326)

# Compute the distance between the reference point and points from 'df_sf'
results <- st_distance(ref_point_sf, df_sf) %>% 
  set_units("km")

Output

results
#> Units: [km]
#>      [,1]     [,2] [,3] [,4] [,5] [,6]
#> [1,]    0 18.85446    0    0    0    0

^{Created on 2021-12-01 by the reprex package (v2.0.1)}