make_data.Rmd

---
title: "Global Human Settlement Layer"
csl: the-american-naturalist.csl
output:
  html_document:
    theme: cerulean
    toc: yes
  pdf_document:
    toc: yes
<!-- bibliography: references.bib -->
editor_options: 
  chunk_output_type: console
---

<!--
IMAGES:
Insert them with: ![alt text](image.png)
You can also resize them if needed: convert image.png -resize 50% image.png
If you want to center the image, go through HTML code:
<div style="text-align:center"><img src ="image.png"/></div>

REFERENCES:
For references: Put all the bibTeX references in the file "references.bib"
in the current folder and cite the references as @key or [@key] in the text.
Uncomment the bibliography field in the above header and put a "References"
title wherever you want to display the reference list.
-->

<style type="text/css">
.main-container {
  max-width: 1370px;
  margin-left: auto;
  margin-right: auto;
}
</style>

```{r general options, include = FALSE}
knitr::knit_hooks$set(
  margin = function(before, options, envir) {
    if (before) par(mgp = c(1.5, .5, 0), bty = "n", plt = c(.105, .97, .13, .97))
    else NULL
  },
  prompt = function(before, options, envir) {
    options(prompt = if (options$engine %in% c("sh", "bash")) "$ " else "> ")
  })

knitr::opts_chunk$set(margin = TRUE, prompt = TRUE, comment = "", eval = FALSE,
                      collapse = TRUE, cache = FALSE, autodep = TRUE,
                      dev.args = list(pointsize = 11), fig.height = 3.5,
                      fig.width = 4.24725, fig.retina = 2, fig.align = "center")

options(width = 137)
```

```{r}
library(sp)
library(raster)
library(ecomore)
library(magrittr)
```

## Utilitary function

```{r}
make_url <- function(yr) {
  root <- paste0("http://cidportal.jrc.ec.europa.eu/ftp/jrc-opendata/GHSL/",
                 "GHS_BUILT_LDSMT_GLOBE_R2015B/GHS_BUILT_LDS")
  globe <- "_GLOBE_R2016A_"
  built <- "/V1-0/GHS_BUILT_LDS"
  ext <- "_v1_0.zip"
  res <- "3857_38"
  paste0(root, yr, globe, res, built, yr, globe, res, ext)
}
```

## Loading the polygon of Vientiane

Downloading the polygons of the provinces of Lao PDR from
[GADM](https://gadm.org/index.html):

```{r}
if (!dir.exists("data-raw")) dir.create("data-raw")
file <- "data-raw/gadm36_LAO_1_sp.rds"
if (!file.exists(file))
  download.file("https://biogeo.ucdavis.edu/data/gadm3.6/Rsp/gadm36_LAO_1_sp.rds", file)
```

Making the polygon of Vientiane prefecture:

```{r}
vientiane <- "data-raw/gadm36_LAO_1_sp.rds" %>% 
  readRDS() %>% 
  subset(NAME_1 == "Vientiane [prefecture]")
```

## Making GHS raster files

The pipeline:

```{r}
if (!dir.exists("data")) dir.create("data")
system.time(for (yr in c(1990, 2000, 2014)) {
  file <- paste0("data-raw/y", yr, ".zip")
  dir <- paste0("GHS_BUILT_LDS", yr, "_GLOBE_R2016A_3857_38_v1_0")
  if (!file.exists(file)) download.file(make_url(yr), file)
  unzip(file)
  yr %>% paste0(dir, "/GHS_BUILT_LDS", ., "_GLOBE_R2016A_3857_38_v1_0_p2.tif") %>% 
    raster() %>% 
    crop_raster(., spTransform(vientiane, crs(.))) %>% 
    writeRaster(paste0("data/builtup", yr, "res38m3857.tif"), "GTiff", overwrite = TRUE)
  unlink(dir, TRUE)
})
```