R/append_height.R

In gtfs2gps: Converting Transport Data from GTFS Format to GPS-Like Records

#' @title Add a column with height to GPS data
#' @description Add a column named height to GPS data using a tif data as reference.
#' @param gps A GPS data created from gtfs2gps().
#' @param heightfile The pathname of a tif file with height data.
#' @return The GPS data with a new column named height.
#' @export
#' @examples
#' \dontrun{
#' # this example takes more than 10s to run
#' library(magrittr)
#' 
#' fortaleza <- system.file("extdata/fortaleza.zip", package = "gtfs2gps")
#' srtmfile <- system.file("extdata/fortaleza-srtm.tif", package = "gtfs2gps")
#' 
#' gtfs <- read_gtfs(fortaleza) %>%
#'   gtfstools::filter_by_shape_id("shape836-I") %>%
#'   filter_single_trip() 
#' 
#' fortaleza_gps <- gtfs2gps(gtfs, spatial_resolution = 500) %>% append_height(srtmfile)
#' }
append_height <- function(gps, heightfile){
  myraster <- terra::rast(heightfile)
  result <-  terra::extract(myraster, gps[, c("shape_pt_lon", "shape_pt_lat")])
  gps$height <- result[, 2]
  return(gps)
}