Exploring New South Wales from my Desktop

Using NSW spatial service layers in R

WMTS
R code
leaflet
Australia
iNaturalist
Author

José R. Ferrer-Paris

Published

May 26, 2024

JR the (virtual) explorer!

Believe it or not, I do not spend my whole time sitting in front of my Desktop computer. Sometimes I do get out and explore this wonderful country, look:

Odontophora observed in Maroubra NSW 2035, Australia by neomapas@iNaturalist Silver Gull observed in Sydney NSW, Australia by neomapas@iNaturalist ** observed in Wentworth St, Randwick, NSW, AU by neomapas@iNaturalist Laughing Kookaburra observed in Prince Street, Randwick, NSW, AU by neomapas@iNaturalist Schoenus subaphyllus observed in Scotia NSW 2648, Australia by neomapas@iNaturalist Exoneura observed in Karloo Pools Walking Track W, Royal Nat’l Park NSW 2233, Australia by neomapas@iNaturalist Leafy Purple Flag observed in La Perouse, Sydney NSW, Australia by neomapas@iNaturalist Purple Rock Crab observed in Manly NSW 2095, Australia by neomapas@iNaturalist Lesser Grass Blue observed in Sydney NSW, Australia by neomapas@iNaturalist Red and Blue Beetle observed in Scotia NSW 2648, Australia by neomapas@iNaturalist Milky Flower Spider observed in Karloo Pools Walking Track W, Royal Nat’l Park NSW 2233, Australia by neomapas@iNaturalist White-browed Scrubwren observed in Blue Mountains Nat’l Park NSW 2787, Australia by neomapas@iNaturalist

But yeah, most of the time I am exploring the world through geospatial data. And since I am clearly obsessed with reproducible workflows, I want to code my way through the process, and make sure I can produce the building blocks for future virtual explorations.

So I asked myself this question, How do I make a good base map for exploring New South Wales (Australia) in as few lines of code as possible? Well it seems NSW Spatial Services has the data that I need!

Today I will create a minimal example for creating a dynamic map using these layers, R and the leaflet package.

Data from Spatial NSW

If you navigate from the NSW Spatial Services to the Web services pages you will find that:

Web services are released under open access licences as part of the NSW Government Open Data Policy to support new and innovative uses of NSW Government digital information.

That is great, lets do some new and innovative uses of the digital information!

There are many data in different themes to choose from: Imagery, Land Cover, Physiography…

The documentation in their webpage focuses on two supported protocols here REST API and WMS, and the favourite GIS software of many users. But what about the few of us with different taste?. I though my use case would fall within the Advanced User Guide, but it seems I still needed to sort out many details to get it to work in R using the leaflet package.

This is how it’s done

Short and sweet in as few lines of code as possible:

# Have you met Leaflet.JS?
library(leaflet)

# URL for the MapServer
NSW_basemap_url <- 
    "http://maps.six.nsw.gov.au/arcgis/rest/services/public/NSW_Base_Map/MapServer/WMTS"

# Build a request for the server
NSW_basemap_layer <- "&layer=public_NSW_Base_Map"

nsw_basemap <- paste0(
    NSW_basemap_url,
    "?Request=GetTile",
    "&Service=WMTS",
    "&Version=1.0.0",
    "&Style=default",
    "&tilematrixset=default028mm",
    "&Format=image/jpgpng",
    NSW_basemap_layer,
    "&TileMatrix={z}",
    "&TileRow={y}",
    "&TileCol={x}"
  )

# Don't forget the attribution
attrib_string <- 
    sprintf(" © State of New South Wales, Department of Customer Service, Spatial Services %s", 
    date()
)

# Create a map with this tile set
leaflet() |>
    setView(lng = 151.2365, lat = -33.916, zoom = 15) |>
    addTiles(urlTemplate = nsw_basemap,
           attribution = attrib_string,
           group = 'NSW basemap'
           )

Code explained

Ok, now let’s go over the code and describe the steps in more detail. This will help you understand the process better and provide more info on how to adapt this example to your needs.

Have you met Leaflet.JS?

I have probably said this before, but Leaflet JS https://leafletjs.com/ is probably the most popular open-source JavaScript library for mobile- and web-friendly interactive maps. With an easy to use and well-documented API, many developers have contributed libraries, modules, plug-ins and interfaces to implement leaflet maps from your favourite programming languages and development platforms. Here we are using the R package https://rstudio.github.io/leaflet/ to integrate these JS functions in R.

library(leaflet)

URL for the MapServer

We need the address of the MapServer that hold the layer we want to display. This step is not as easy as it should be, but with patience you will get there. The spatial portal has so many levels of information, you can easily click around in circles without getting the info you need.

So here is one possible way NOT to get there:

So finally we have the URL:

# URL for the MapServer
NSW_basemap_url <- 
    "http://maps.six.nsw.gov.au/arcgis/rest/services/public/NSW_Base_Map/MapServer/WMTS"

Build a request for the server

Now we need to build a request for the server.

This starts with getting the capabilities of the server by visiting this url in a browser:

paste0(NSW_basemap_url, "?Request=GetCapabilities")
[1] "http://maps.six.nsw.gov.au/arcgis/rest/services/public/NSW_Base_Map/MapServer/WMTS?Request=GetCapabilities"

You will get a document in XML format that has the information we need for the next request.

For example the layer identifier:

<Layer>
<ows:Title>public_NSW_Base_Map</ows:Title>
<ows:Identifier>public_NSW_Base_Map</ows:Identifier>
...

Also Style:

<Style isDefault="true">
<ows:Title>Default Style</ows:Title>
<ows:Identifier>default</ows:Identifier>
</Style>

And others…

And then we concatenate the mapserver url and the layer name with a couple of parameters needed in our WMTS GetTile request:

nsw_basemap <- paste0(
    NSW_basemap_url,
    # Service (version) request 
    "?Service=WMTS", 
    "&Request=GetTile", 
    "&Version=1.0.0", 
    # the following need to match the details in the GetCapabbilities request
    "&Style=default", # usually there is only one style
    "&tilematrixset=default028mm", # usually default028mm or GoogleMapsCompatible
    "&Format=image/png", # check the available format, sometime it is image/jpgpng
    "&layer=public_NSW_Base_Map", # check the name of the layer
    # The x,y,z dimensions dynamically requested
    # based on the zoom and coordinates of the viewer window
    "&TileMatrix={z}", 
    "&TileRow={y}",
    "&TileCol={x}"
  )

Don’t forget the attribution

attrib_string <- 
    sprintf(" © State of New South Wales, Department of Customer Service, Spatial Services %s", 
    date()
)

Create a map with this tile set

leaflet() |>
    setView(lng = 151.2365, lat = -33.916, zoom = 15) |>
    addTiles(urlTemplate = nsw_basemap,
           attribution = attrib_string,
           group = 'NSW basemap'
           )

And here some bonus tips

Other layers from same base URL 😀

Now that this is working, I got curious about other layers available in the same portal.

Some of the sources have the same base url and we just need to change the name of the layer, for example we can use a function in package stringr to replace the base map with imagery:

library(stringr)
nsw_imagery <- str_replace_all(nsw_basemap, "NSW_Base_Map", "NSW_Imagery") 
leaflet() |>
  setView(lng = 151.2365, lat = -33.916, zoom = 14) |>
  addTiles(urlTemplate = nsw_imagery,
           attribution = attrib_string
           )

Other layers from other base URL 😕

I also found historical aerial photographs, but the base url is different and for some reason I have been unable to create a request that works in leaflet, this code seems to be right, but the result is blank:

nsw_historical <- paste0(
    "https://portal.spatial.nsw.gov.au/tileservices/Hosted/HistoricalImagery1947/MapServer/",
    "WMTS?",
    "Request=GetTile",
    "&Service=WMTS",
    "&Version=1.0.0",
    "&Style=default",
    "&tilematrixset=default028mm",
    "&Format=image/jpgpng",
    "&layer=HistoricalImagery1947",
    "&TileMatrix={z}",
    "&TileRow={y}",
    "&TileCol={x}"
  )
leaflet() |>
  setView(lng = 151.2365, lat = -33.916, zoom = 14) |>
  addTiles(urlTemplate = nsw_historical,
           attribution = attrib_string
           )

There are also some datsets using Vector tile layers, for example:

https://portal.spatial.nsw.gov.au/vectortileservices/rest/services/Hosted/NSW_BaseMap_VectorTile_Hybrid/VectorTileServer

I haven’t yet figured out how to add them in Leaflet.

Multiple layers in one map 🌐

Now we have at least two base layers, and we would like to display both in a map. We can do that with help of the addLayersControl function using the argument baseGroups to identify the groups of layers to choose from:

leaflet() |>
  setView(lng = 151.2365, lat = -33.916, zoom = 14) |>
  addTiles(urlTemplate = nsw_basemap,
           attribution = attrib_string,
           group = 'NSW base map'
           ) |>
   addTiles(urlTemplate = nsw_imagery,
           attribution = attrib_string,
           group = 'NSW imagery'
           ) |>
    addLayersControl(
        baseGroups = c("NSW imagery", "NSW base map"))

Conclusion

Here we use R and leaflet to load geospatial layers using WMTS services. Thanks to NSW Spatial service for the awesome products!

Here the basic recipe:

  • Find the WMTS server,
  • Send a GetCapabilities request
  • Identify the layer of interest and other parameters,
  • Build your WMTS request,
  • Add the layer to your leaflet map using the addTile function
  • Optional:
    • Repeat with other layers
    • Add a layers control with addLayersControl function
  • Done!

I hope this makes it easier for you to create your maps visualisations with R. Enjoy!