Untitled
In ozmaps: Australia Maps

knitr::opts_chunk$set(echo = TRUE)

Detailed data (WIP)

The material below doesn't actually match this package yet, this is just here for now until simplifying the lga and electoral boundaries is done.

Obtain a set of polygon map files

This block of code will download a ~1.5Gb zip file with many shapefiles in nested folders.

I discovered these links (ESRI Shapefile and MapInfo) at this site: https://data.gov.au/dataset/psma-administrative-boundaries

I originally chose the MapInfo format, but those had empty geometries(!).

Build a data frame of the available file names, it's a recursive tree of directories but we only need the ".shp$" values.

## ignore state and see what layers there are
## there are 32 different kinds of layers
sort(unique(unlist(lapply(strsplit(fs$file, "_"), function(x) paste(tail(x, -1), collapse = "_")))))

No we can filter on the state-removed strings to get the entire set for the country.

## all LGA
lga <- read_psma(fs %>% dplyr::filter(grepl("LGA_POLYGON", file)) %>% dplyr::pull(fullname))

## note that the "geometry" column is sticky, we
## subset like this to avoid faceting on all columns
plot(lga[1])

## electoral
elec <- read_psma(fs %>% dplyr::filter(grepl("STATE_ELECTORAL_POLYGON", file)) %>% dplyr::pull(fullname))

plot(elec[1])

## state
state <- read_psma(fs %>% dplyr::filter(grepl("STATE_POLYGON", file)) %>% dplyr::pull(fullname))
plot(state[1])
abline(v = 148, h = -43)

## that is very high resolution, checkout 
plot(state[1], xlim = c(147.7, 148.2), ylim = c(-43.3, -43.0))
abline(v = 148, h = -43)

pryr::object_size(state)

## use rmapshaper for topological simplification
## (but avoid date columns which trigger a bug in 0.3.0)
simple_state <- rmapshaper::ms_simplify(state[c("ST_PLY_PID", "STATE_PID", "geometry")])
pryr::object_size(simple_state)
plot(simple_state[1], xlim = c(147.7, 148.2), ylim = c(-43.3, -43.0))
plot(simple_state[1])

Another location.

## that is very high resolution, checkout 
plot(state[1], xlim = c(146.7, 148.2), ylim = c(-44.3, -43.0))
abline(v = 147.2385, h = -43.46973)

plot(state[1], xlim = 147.2385 + c(-1, 1)/30, 
     ylim = -43.46973 + c(-1, 1)/30, border = NA)

plot(st_geometry(simple_state), add = TRUE)
abline(v = 147.2385, h = -43.46973)