Posts – GeospatialStuff

Note: some posts show code that has been superseded. Code ran as written at last modified dates.

A geometric origami classic

origami

life

Not geospatial stuff, but most certainly spatial stuff. Thomas Hull’s classic ‘Five intersecting tetrahedra’, which I’ve always wanted to make, but never quite got around to until now.

David O’Sullivan

A simple atlas of projections

Blog post interactivity using marimo

python

tutorial

marimo

projections

The marimo quarto extension lets you make markdown posts with embedded reactive python code which can be written in any old order you like (just like observable notebooks).

David O’Sullivan

What three letters

Word games all the way to the ends of the earth

geospatial

R

tutorial

networks

ggplot

life

Maps of all the possible air routes where the origin and destination airport IATA codes would differ by only one letter, and of the ones that actually do. Also, grobs.

David O’Sullivan

A population based binary space partition

Of course there’s a point, I’m just not sure what

geospatial

R

tutorial

aotearoa

population

cartography

A process for building a hierarchical partition of a gridded population dataset

David O’Sullivan

How to cut a cake into four equal slices

If the cake is a country made of people

geospatial

R

tutorial

aotearoa

A procedure, including R code, for quadrisecting the population of New Zealand with two lines that intersect at 90°

David O’Sullivan

North-south or east-west islands?

And why both are wrong

geospatial

R

tutorial

stuff

aotearoa

An exploration of just how north is Te Ika-a-Maui and how south is Te Waipounamu.

David O’Sullivan

Look ma! (Almost) no javascript!

I gave a talk at the local python meetup

geospatial

python

maps

tiling

cartography

weaving

visualization

Video of a talk about marimo that I gave to the local python meetup, and related links.

David O’Sullivan

Nine XKCD bad map projections: ranked!

Also: reverse-engineered

geospatial

R

tutorial

stuff

cartography

xkcd

An attempt to rank the nine examples of so-called ‘bad map projections’ published by the XKCD web comic over the last few years. Not all the projections are actually bad, and I managed to reproduce some in R.

David O’Sullivan

Mostly tiles, but also glyphs

And tiles as glyphs

python

cartography

visualization

tiling

aotearoa

An exploration of some tile-based mapping options dealing with three variables, and a consideration of the relationship between tiles and glyphs in maps.

David O’Sullivan

Imagine setting up a Jupyter hub

It’s easy if you try

python

training

aotearoa

Turns out it is actually really easy to setup a Jupyter hub! So easy, even I couldn’t mess it up, when I actually read the instructions.

David O’Sullivan

MapWeaver: tiled and woven multivariate maps without code

How can I make this better? And: is this anything?!

maps

tmap

tiling

weaving

python

Early experiences using Marimo to make a web app from the weavingspace code.

David O’Sullivan

Marimo notebooks

Reactive notebooks in python!

python

tutorial

Marimo is a reactive notebook (like Observable) but for Python. It’s a really nice idea and I can imagine using it quite a lot.

David O’Sullivan

Into the (LiDAR) void

Or: who’s afraid of the Tararuas?

aotearoa

maps

tmap

geospatial

R

tutorial

life

Reflections on tramping in the (very) gnarly Tararuas, with R code for making elevation transects.

David O’Sullivan

Random points on the globe revisited

Of Christmas gifts and rabbit holes

geospatial

R

tutorial

life

Revisiting the generation of evenly-space point patterns on the globe, sparked by a rather lovely board game.

David O’Sullivan

A welcome (re)emergence of systems thinking

And it’s not before time!

complexity

aotearoa

conferences

systems

Some (positive) thoughts on a surprise encounter with systems thinking at a project away day.

David O’Sullivan

ALGIM 2024

On geospatial in local government

local government

geospatial

aotearoa

conferences

I don’t think I ever imagined attending a local government information management conference, but I did, and here are some thoughts on the experience.

David O’Sullivan

tmap vs. ggplot2 for mapping

I think I prefer…

geospatial

R

qgis

tutorial

tmap

ggplot

For me at least the choice between ggplot2 and tmap is an ongoing question. Here are my latest thoughts on the subject (with code).

David O’Sullivan

The joy of DuckDB

Insert duck-related joke here

geospatial

duckdb

R

tutorial

DuckDB: for once a technology people are excited about that isn’t a disappointment!

David O’Sullivan

In praise of GeoPackages

Shapefiles… who needs ’em?

geospatial

R

qgis

tutorial

One of the mysteries of the geospatial universe is the persistence of the shapefile. My thoughts, with example R code, on why we should all be using GeoPackages instead.

David O’Sullivan

Giscience 2025

You know you want to…

conferences

geospatial

aotearoa

Call for papers.

David O’Sullivan

GeoCart’2024

Reflections on the meeting

cartography

geospatial

aotearoa

conferences

time-space

GeoCart never disappoints, and this year was no exception. Even so the conference could probably do with a few minor adjustments to its format.

David O’Sullivan

Useful utilities for NetLogo

For when you are missing R/python

netlogo

simulation

I’ve made some useful utility functions for NetLogo that make it easier to manages lists and generate random numbers with different distributions.

David O’Sullivan

The model zoo

Keeping up with NetLogo

netlogo

books

simulation

Notice of an update to the models associated with Spatial Simulation.

David O’Sullivan

Experiments with R interpolators

Doing projection using a triangulation interpolator

R

geospatial

tutorial

It’s possible to generate arbitrary transformation of geographical space using the kinds of interpolators used by engineers for finite element analysis. Here’s how.

David O’Sullivan

Spiral origami

Things to make and do

javascript

origami

stuff

I made a weird javascript thing that produces crease patterns you can use to fold Tomoko Fuse’s spiral origami.

David O’Sullivan

OK COVID, you win

The end of the line

visualization

covid

R

maps

The sorry tale of how I (and the country) gave up on managing COVID.

David O’Sullivan

Low level handling of sf objects

Goddamnit, floating point!

R

geospatial

Probably you won’t ever find yourself making simple features geometries from scratch, but if you do, here are some things you should know.

David O’Sullivan

Locations of interest in 2021 delta outbreak

When everything went pear-shaped

maps

visualization

covid

The delta outbreak of COVID in August 2021 was the beginning of the end for New Zealand’s pandemic response. Here’s an animated map timeline of the cases.

David O’Sullivan

Inverse distance weighted (IDW) interpolation using spatstat

So many packages so little time

R

geospatial

tutorial

You can do inverse-distance weighted interpolation in the spatstat package, but it’s a little bit fiddly. This post has code examples to show you how.

David O’Sullivan

Kernel density estimation in R spatial

Here’s one way to do kernel density estimation in R spatial

R

geospatial

tutorial

The spatstat package is incredibly powerful but has no interest in dealing with your GIS data. Here’s how to use it to do kernel density estimation on ‘real’ data.

David O’Sullivan

Uniform random points on the globe

The earth’s a sphere: who knew?

R

geospatial

tutorial

Generating randomly distributed evenly spaced points on the sphere takes some care. This post explores why and how.

David O’Sullivan

Mapping the Dulux colours

The ultimate in categorical mapping

R

geospatial

stuff

maps

aotearoa

The ‘Dulux colours of New Zealand’ are crying out to this geographer at least to be mapped, so I gave it a try.”

David O’Sullivan

Affine transformations of sf objects

Manipulating simple features in sf is sorta simple, sorta not…

R

geospatial

tutorial

Did you know the sf package lets you add vectors to geometries and multiply them by affine transformation matrices? Well, it does, and here are some examples.

David O’Sullivan

What three chords

Seriously, WTC?!

javascript

geospatial

stuff

A rather silly exploration of encoding spatial location using guitar chords (lots of them, but only three at a time).

David O’Sullivan