How to get GPS coordinates with leaflet.extras addControlGPS - r

Question

I'm using the leaftlet.extras R package to add Gps control inside a map.
I'm using the extension addControlGPS inside my code :
... %>%
addControlGPS(options = gpsOptions(position = "topleft", activate = TRUE,
autoCenter = TRUE, maxZoom = 60,
setView = TRUE)) %>%
...
The controller works ok.
I need to extract the Gps coordinates to re-use in my code as arguments for other functions. Is there any way to do that ?

Answer 1

Every time the gps location updates, the coordinates are written to map.id+'_gps_located'. You can find all leaflet.extras bindings in the htmlwidgets/bindings folder in their git.
Working example
library(leaflet)
library(leaflet.extras)
library(shiny)
ui <- fluidPage(
leafletOutput('map')
)
server <- function(input, output, session) {
output$map <- renderLeaflet({ leaflet()%>%addTiles() %>%
addControlGPS(options = gpsOptions(position = "topleft", activate = TRUE,
autoCenter = TRUE, maxZoom = 60,
setView = TRUE))})
observe(
print(input$map_gps_located)
)
}
shinyApp(ui, server)

Answer 2

I've recently had a similar problem with an app I was working on.
You can extract the gps coordinates from a leaflet map by using the _marker_click feature, where is the map label you specify as an output for the leaflet rendering statement.
In my case here's the chunk of code I used to retrieve the coords. In my case the output name of the map object was parksMap therefore the full input to consider in the event observation was parksMap_marker_click. This statement can be saved in a variable (in my case pin), that stores the coordinates data. Finally you need to wrap it all in a reactive expression to be able to save every coordinate when clicking on a point in the leaflet map.
# code to load the park card once the click event on a marker is intercepted
observeEvent(input$parksMap_marker_click, {
pin <- input$parksMap_marker_click
#print(Sys.time()) #uncomment to log coords
#print(pin) #uncomment to log coords
selectedPoint <- reactive(parks[parks$Latitude == pin$lat & parks$Longitude == pin$lng,])
leafletProxy("parksMap", data = selectedPoint()) %>% clearPopups() %>%
addPopups(~Longitude,
~Latitude,
popup = ~park_card(selectedPoint()$ParkName, selectedPoint()$ParkCode, selectedPoint()$State, selectedPoint()$Acres, selectedPoint()$Latitude, selectedPoint()$Longitude)
)
})
The full github repo of the app is available here.