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Calculate travel time

Source: R/calculate_travel_time.R
calculate_travel_time.Rd

Calculate the travel time from a set of points over a friction surface.

Usage

calculate_travel_time(
  friction_surface,
  points,
  filename = NULL,
  overwrite = FALSE
)

Arguments

friction_surface

A SpatRaster friction surface layer. See ?get_friction_surface

points

A two-column matrix, data.frame, or tibble with longitude (x) in the first column and latitude (y) in the second, or a SpatVector, in the same coordinate, reference system as friction_surface.

filename

character. Output file name with extension suitable for terra::writeRaster

overwrite

logical. If TRUE filename is overwritten.

Value

SpatRaster

Details

Implements methods from Weiss et al. 2018, 2020 to calculate travel time from given locations over a friction surface.

Over large areas this function can require significant RAM and will be slow.

Citations: D. J. Weiss, A. Nelson, C. A. Vargas-Ruiz, K. Gligoric, S., Bavadekar, E. Gabrilovich, A. Bertozzi-Villa, J. Rozier, H. S. Gibson, T., Shekel, C. Kamath, A. Lieber, K. Schulman, Y. Shao, V. Qarkaxhija, A. K. Nandi, S. H. Keddie, S. Rumisha, P. Amratia, R. Arambepola, E. G. Chestnutt, J. J. Millar, T. L. Symons, E. Cameron, K. E. Battle, S. Bhatt, and P. W. Gething. Global maps of travel time to healthcare facilities. (2020) Nature Medicine. https://doi.org/10.1038/s41591-020-1059-1

D. J. Weiss, A. Nelson, H.S. Gibson, W. Temperley, S. Peedell, A. Lieber, M. Hancher, E. Poyart, S. Belchior, N. Fullman, B. Mappin, U. Dalrymple, J. Rozier, T.C.D. Lucas, R.E. Howes, L.S. Tusting, S.Y. Kang, E. Cameron, D. Bisanzio, K.E. Battle, S. Bhatt, and P.W. Gething. A global map of travel time to cities to assess inequalities in accessibility in 2015. (2018). Nature. doi:10.1038/nature25181.

Examples


ext <- matrix(
  data = c("111", "0", "112", 1),
  nrow = 2,
  ncol = 2,
  dimnames = list(
    c("x", "y"),
    c("min", "max")
   )
 )

 friction_surface <- get_friction_surface(
   surface = "motor2020",
   extent = ext
 )
#> Registered S3 methods overwritten by 'malariaAtlas':
#>   method              from     
#>   autoplot.SpatRaster tidyterra
#>   autoplot.default    ggplot2  
#> Checking if the following Surface-Year combinations are available to download:
#> 
#>     DATASET ID  YEAR 
#>   - Explorer__2020_motorized_friction_surface:  DEFAULT 
#> 
#> Loading required package: sf
#> Linking to GEOS 3.10.2, GDAL 3.4.1, PROJ 8.2.1; sf_use_s2() is FALSE
#> No encoding supplied: defaulting to UTF-8.
#> <GMLEnvelope>
#> ....|-- lowerCorner: 0 111
#> ....|-- upperCorner: 1 112Start tag expected, '<' not found

 from_here <- data.frame(
   x = c(111.2, 111.9),
   y = c(0.2, 0.35)
 )

 calculate_travel_time(
  friction_surface = friction_surface,
  points = from_here
 )
#> class       : SpatRaster 
#> dimensions  : 120, 120, 1  (nrow, ncol, nlyr)
#> resolution  : 0.008333333, 0.008333333  (x, y)
#> extent      : 111, 112, 0, 1  (xmin, xmax, ymin, ymax)
#> coord. ref. :  
#> source(s)   : memory
#> name        : travel_time 
#> min value   :      0.0000 
#> max value   :    582.1882