Kerbals on the Mun
image wikimedia.commons

Simulation models

Time, process, dynamics

Simple simulations

Complicated simulations

image from Harold Lloyd's classic silent comedy
Safety Last! 1923 from the book An American Comedy

Time

Time geography poses many questions about how well we deal with time

(spoilers: not very)

Most map-oriented methods are ‘snapshot-based’

Comics

ESA Rosetta mission comet landing as rendered by xkcd.com
and archived by MagicalTux

McCloud S. 1993. Understanding Comics: The Invisible Art
William Morrow, NY, page 94.
McCloud S. 1993. Understanding Comics: The Invisible Art
William Morrow, NY, pages 100-101.

Reading animated maps remains challenging

my map of locations of interest in the 2021 COVID-delta outbreak

Another example

Animation from the police-shootings data made
using tm_facets and tm_animation

Eadweard [sic] Muybridge's Horse in Motion
image source Library of Congress
see also this extraordinary documentary

So... for now, time and process are ‘hidden’ by maps

Let's try simulations instead

source wikimedia.commons

Simple simulations

Entities in a simulation have behaviour not just state

Behaviour leads to state changes, and often depends on the state of neighbouring entities

‘Game of Life’

To play more and see the code, go here.
See here for more details.

Devised by John Conway in the 1970s

A cellular automaton

Lattice of cells, each alive (black) or dead (white)

3 live neighbours → birth

2 or 3 live neighbours → survival

Voter model

To play more and see the code, go here.
See here for more details.

Simple model of ecological patch dynamics

Each generation every cell changes to match one of its four neighbors picked at random

Competition playing out in space over time

Growth model

To play more and see the code, go here.
See here for more details.

Simple simulation of spatial spread

Each step an already occupied cell causes one of its four neighbors to become occupied

Intricate structures are apparent when we colour cells by time occupied

Simple simulations of disease spread, urban growth use this mechanism

Mark Rothko's Black on Maroon 1958, 2667 x 3812 mm
Tate Gallery, image source tate.org.uk

Simple but complex

Even simple models show systems may be unpredictable in detail...

Even if we know fully how they work!


Such simulations are useful for theory, but for real world applications we usually need something more complicated

Complicated simulations

Army Corps of Engineers San Francisco Bay model
in Sausalito, image source wikimedia.commons

Complicated simulations

This isn’t super complicated, but it’s complicated enough!

See: O’Sullivan D, M Gahegan, DJ Exeter and B Adams. 2020. Spatially explicit models for exploring COVID 19 lockdown strategies. Transactions in GIS 24(4) 967–1000.

Bill Phillips's MONIAC (Monetary National Income
Analogue Computer) hydraulic model of the economy
developed at LSE in the 1950s, image source LSE Library archives.
They also have one at the Reserve Bank!

Other examples

Models of the macro-economy

Global circulation models of climate system

Meteorological models

Simulations of traffic, crowds, evacuations, etc.

Building and street design

Serious play?

source redfish.com

Broader context for this example is in this report

Seriously, play

source simcity.com

Summary

Even digital maps are a static medium

Process hidden, must be inferred

Simulation is an alternative approach

Simple simulations can be useful for developing theory

More complicated (realistic?) simulations preferred for decision support