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https://github.com/riatelab/tanaka

Tanaka Maps with R
https://github.com/riatelab/tanaka

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Tanaka Maps with R

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README 

        



# Tanaka 



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Also called "relief contours method", "illuminated contour method" or "shaded 

contour lines method", the Tanaka method[1](#fn1) 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 paper[2](#fn2). 



`tanaka` is a small package with two functions:



- `tanaka()` uses a `terra` object and displays the map directly;

- `tanaka_contour()` builds the isopleth polygon layer. 



The contour lines creation relies on [`mapiso`](https://github.com/riatelab/mapiso), 

spatial manipulation and display rely on [`sf`](https://github.com/r-spatial/sf). 



## Installation

* From CRAN

```r

install.packages("tanaka")

```



* Development version on GitHub

```r

require(remotes)

install_github("riatelab/tanaka")

```



## Demo



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

```r

library(tanaka)

library(terra)

ras <- rast(system.file("tif/elev.tif", package = "tanaka"))

tanaka(ras, breaks = seq(80,400,20), 

       legend.pos = "topright", legend.title = "Elevation\n(meters)")

```

![](https://raw.githubusercontent.com/riatelab/tanaka/master/img/ex1.png)  



* This example is based on an  elevation raster downloaded via 

[`elevatr`](https://github.com/jhollist/elevatr). 

```r

library(tanaka)

library(elevatr)

library(terra)

# 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 = "EPSG:4326", clip = "locations")

ras <- rast(ras)

# 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)

```

![](https://raw.githubusercontent.com/riatelab/tanaka/master/img/ex2.png)  



* The last example illustrates the use of tanaka with non-topographical data. 

This map is based on the [Global Human Settlement Population Grid](https://ghsl.jrc.ec.europa.eu/ghs_pop.php) (1km). 



```r

library(terra)

library(sf)

library(tanaka)

library(mapsf)

# Download

tempzip <- tempfile()

tempfolder <- tempdir()

data_url <- paste0("http://cidportal.jrc.ec.europa.eu/ftp/jrc-opendata/GHSL/", 

                   "GHS_POP_GPW4_GLOBE_R2015A/GHS_POP_GPW42015_GLOBE_R2015A_54009_1k/", 

                   "V1-0/GHS_POP_GPW42015_GLOBE_R2015A_54009_1k_v1_0.zip")

download.file(data_url, tempzip)

unzip(tempzip, exdir = tempfolder)

# Import

pop2015 <- rast(paste0(tempfolder, 

                       "/GHS_POP_GPW42015_GLOBE_R2015A_54009_1k_v1_0/",

                       "GHS_POP_GPW42015_GLOBE_R2015A_54009_1k_v1_0.tif"))

# Mask raster

center <- st_as_sf(data.frame(x=425483.8, y=5608290), 

                   coords=(c("x","y")), 

                   crs = st_crs(pop2015))

center <- st_buffer(center, dist = 800000)

ras <- crop(pop2015, st_bbox(center)[c(1,3,2,4)])

# Smooth values

mat <- focalMat(x = ras, d = c(10000), type = "Gauss")

rassmooth <- focal(x = ras, w = mat, fun = sum, na.rm = TRUE)

# Map

bks <- c(0,25,50,100,250,500,750,1000,1750,2500,5000, 7500,10000)

mf_export(x = center, filename = "circle.png", width = 800, res = 100)

tanaka(x = rassmooth,

       breaks = bks,

       mask = center,

       col = hcl.colors(n = 12, palette = "Inferno"),

       shift = 2500,

       add = TRUE,

       legend.pos = "topleft",

       legend.title = "Inhabitants\nper km2")

mf_map(center, add = TRUE, border = "white", col = NA, lwd = 6)

mf_title(txt = "Smoothed Population Density")

mf_credits(paste0("T. Giraud, 2022\n",

                  "Data : European Commission, Joint Research Centre (JRC); ", 

                  "Columbia University, CIESIN (2015): GHS population grid, ", 

                  "derived from GPW4."))

text(-250000 ,6420000, "Gaussian filter, sigma = 10km", 

     adj = 0, font = 3, cex = .8, xpd = TRUE )

dev.off()

```



![](https://raw.githubusercontent.com/riatelab/tanaka/master/img/circle.png)



## Alternative Package

The [`metR` package](https://CRAN.R-project.org/package=metR) allows to draw [Tanaka contours with ggplot2](https://eliocamp.github.io/metR/reference/geom_contour_tanaka.html).



-------------------------------------------



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.