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Get friction surface

Source: R/get_friction_surface.R
get_friction_surface.Rd

Wrapper function to download friction surfaces via malariaAtlas::getRaster().

Usage

get_friction_surface(
  surface = c("motor2020", "walk2020"),
  filename = NULL,
  overwrite = FALSE,
  extent = NULL
)

Arguments

surface

"motor2020" or "walk2020.

filename

character. File name for output layer.

overwrite

Overwrite filename if exists

extent

Spatial extent as one of:

  • a numeric vector specifying c(xmin, xmax, ymin, ymax),

  • a terra SpatExtent, SpatVector, or SpatRaster from which the extent will be taken, or

  • or 2x2 matrix

See details

Value

SpatRaster

Details

Convenience wrapper to malariaAtlas::getRaster() to access motorised and walking travel friction layers per Weiss et al. 2020, that adds safety to check existing files before download. Surfaces can be downloaded directly from: https://malariaatlas.org/project-resources/accessibility-to-healthcare/.

Here —

  • surface = "motor2020" will download "Explorer__2020_motorized_friction_surface", and

  • surface = "walk2020" will download "Explorer__2020_walking_only_friction_surface".

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

extent is formatted and then passed through to malariaAtlas::getRaster() as a 2x2 matrix. It is converted into a matrix using ext_matrix. The matrix format used is as returned by sf::st_bbox() — the first column has the minimum, the second the maximum values; rows 1 & 2 represent the x & y dimensions respectively: matrix(c("xmin", "ymin", "xmax", "ymax"), nrow = 2, ncol = 2, dimnames = list(c("x", "y"), c("min", "max"))). NULL extent downloads (large) global layer.

Troubleshooting: if you get a warning Failed to connect to MAP geoserver, this is an issue with fetching the friction surface using malariaAtlas::getRaster, and not an issue with traveltime itself. The server may be down or there may be an issue with that package.

Examples


# for more examples of passing exten types see ?ext_matrix

ext <- c(111, 112, 0, 1)

 get_friction_surface(
   surface = "motor2020",
   extent = ext
 )
#> Checking if the following Surface-Year combinations are available to download:
#> 
#>     DATASET ID  YEAR 
#>   - Accessibility__202001_Global_Motorized_Friction_Surface:  DEFAULT 
#> 
#> No encoding supplied: defaulting to UTF-8.
#> Opening and ending tag mismatch: hr line 5 and body
#> Opening and ending tag mismatch: body line 3 and html
#> Premature end of data in tag html line 1
#> <GMLEnvelope>
#> ....|-- lowerCorner: 0 111
#> ....|-- upperCorner: 1 112
#> No encoding supplied: defaulting to UTF-8.
#> Opening and ending tag mismatch: hr line 5 and body
#> Opening and ending tag mismatch: body line 3 and html
#> Premature end of data in tag html line 1
#> Start tag expected, '<' not found
#> class       : SpatRaster 
#> dimensions  : 120, 120, 1  (nrow, ncol, nlyr)
#> resolution  : 0.008333333, 0.008333333  (x, y)
#> extent      : 111, 112, 3.774758e-15, 1  (xmin, xmax, ymin, ymax)
#> coord. ref. : lon/lat WGS 84 (EPSG:4326) 
#> source      : Accessibility__202001_Global_Motorized_Friction_Surface_0,111,1,112.tif 
#> name        : friction_surface