Tanaka Method

Also called "relief contours method", "illuminated contour method" or "shaded contour lines method", the Tanaka method¹ enhances the representation of topography on a map by using shaded contour lines. The result is a 3D-like map.

This package is a simplified implementation of the Tanaka method, north-west white contours represent illuminated topography and south-east black contours represent shaded topography. Even if the results are quite satisfactory, a more refined method could be used based on the Kennelly and Kimerling's paper².

tanaka is a small package with two functions:

• tanaka() uses a raster object and displays the map directly;
• tanaka_contour() builds the isopleth polygon layer.

The contour lines creation relies on isoband, spatial manipulation and display relie on sf.

Installation

• Development version on GitHub

require(remotes)
install_github("rCarto/tanaka")

Demo

This example is based on the dataset shipped within the package.

library(tanaka)
library(raster)
ras <- raster(system.file("grd/elev.grd", package = "tanaka"))
tanaka(ras, breaks = seq(80,400,20), 
       legend.pos = "topright", legend.title = "Elevation\n(meters)")

This example is based on an elevation raster downloaded via elevatr.

library(tanaka)
library(elevatr)
# use elevatr to get elevation data
ras <- get_elev_raster(locations = data.frame(x = c(6.7, 7), y = c(45.8,46)),
                       z = 10, prj = "+init=epsg:4326", clip = "locations")
# custom color palette
cols <- c("#F7E1C6", "#EED4C1", "#E5C9BE", "#DCBEBA", "#D3B3B6", "#CAA8B3", 
          "#C19CAF", "#B790AB", "#AC81A7", "#A073A1", "#95639D", "#885497", 
          "#7C4692", "#6B3D86", "#573775", "#433266", "#2F2C56", "#1B2847")
# display the map
tanaka(ras, breaks = seq(500,4800,250), col = cols)

1: Tanaka, K. (1950). The relief contour method of representing topography on maps. Geographical Review, 40(3), 444-456.
2: Kennelly, P., & Kimerling, A. J. (2001). Modifications of Tanaka's illuminated contour method. Cartography and Geographic Information Science, 28(2), 111-123.