dafishr (version 1.0.1)

clean_land_points: Clean points falling inland

Description

This functions eliminates points falling inland by using st_difference() function from the sf package.

Usage

clean_land_points(x, mx_inland = mx_inland)

Value

A data.frame object

Arguments

x

A data.frame containing latitude and longitude coordinates of vessels tracks to be cleaned by land area

mx_inland

is a shapefile loaded with the packages representing inland Mexico area, it can be uploaded with data("mx_inland)

Warning

This function takes a while!! To test you can use the dplyr::sample_n() function as it is shown in the example.

Details

Points falling inland in Vessel Monitoring System, VMS, dataset are obvious mistakes, thus need to be eliminated from the data. The function calls a stored shapefile mx_inland which is a custom sf object created using a coastline buffer to avoid eliminating points because of lack of precision within the shapefiles. The function works with any dataset containing coordinate points in crs = 4326 and named latitude and longitude. See first example with a non-VMS dataset. A second example below shows the usage on VMS sample data.

Examples

# with non VMS data
x <- data.frame(
  longitude = runif(1000, min = -150, max = -80),
  latitude = runif(1000, min = 15, max = 35)
)
data("mx_inland")
x <- clean_land_points(x, mx_inland)

# using sample_dataset

data("sample_dataset", "mx_inland")

vms_cleaned <- vms_clean(sample_dataset)
vms_no_land <- clean_land_points(vms_cleaned, mx_inland)

# You can check the results by plotting the data

vms_cleaned_sf <- sf::st_as_sf(vms_cleaned, coords = c("longitude", "latitude"), crs = 4326)

vms_no_land_sf <- sf::st_as_sf(vms_no_land, coords = c("longitude", "latitude"), crs = 4326)

library(ggplot2)
ggplot(vms_cleaned_sf) +
  geom_sf(col = "red") +
  geom_sf(data = vms_no_land_sf, col = "black")

# in the provided example only few inland points are eliminated.
# There are more evident one within historical data.