World Population

Some feedback on my last post expressed surprise that Ptolemy’s specification of the Oikoumene now holds holds 80.6% of the world’s population. Above (click to zoom), I have redrawn the classic bar charts of world population which explain this fact. Africa, Asia, and Europe contain about 86% of the world’s population. Ptolemy excluded what we now know to be Southern Africa (which only drops the total to 85%) and didn’t extend his Oikoumene quite far enough to the east.

The chart below shows the same thing, but using NASA’s image of the Earth at night. It can be seen that the spikes on the bar chart correspond to major cities.

The Oikoumene of Ptolemy

I was reading recently about the Geographia of Ptolemy (written around 150 AD). This classic book applied Greek mathematical skills to mapping and map projection – and if there was one thing the Greeks were good at, it was mathematics. According to Neugebauer, Ptolemy believed the Oikoumene, the inhabited portion of the world, to range from Thule (63° North) to 16°25′ South, and 90 degrees East and West of Syene in Egypt.

The map above illustrates this Oikoumene, with a modern population overlay in red (data from SEDAC). Ptolemy was not too far wrong – today this region holds 80.6% of the world’s population, and the percentage would have been greater in antiquity.

Also shown on the map are some of the many cities listed in the Geographia. Open circles show Ptolemy’s coordinates (from here, adjusted to a Syene meridian), and filled circles show true positions. Ptolemy had reasonably good latitude values (an average error of 1.2° for the sample shown on the map), but much worse longitude values (an average error of 6.8°). The longitude error is mostly systemic – Ptolemy’s estimate of 18,000 miles or 29,000 km for the circumference of the earth was only 72% of the true value (several centuries earlier, Eratosthenes had come up with a much better estimate). If Ptolemy’s longitudes are adjusted for this, the average error is only 1.5°.

However, Ptolemy’s book deserves considerable respect – it is not surprising that it was used for more than a thousand years.

World Solar Challenge September 3 update

In the leadup to the 2019 Bridgestone World Solar Challenge in Australia this October, most cars have been revealed (see my recently updated illustrated list of teams), with JU’s reveal a few days ago (see below), and Tokai’s reveal due in a few hours.

There are now 9 international teams in Australia (more than the number of local teams). Eindhoven (#40), Agoria (#8), and part of Vattenfall (#3) are driving north to Darwin, while Top Dutch (#6) have a workshop in Port Augusta (and living quarters in Quorn).

JU’s solar car Axelent (photo credit)

The chart below shows progress in submitting compulsory design documents for the race. White numbers highlight eight teams with no visible car or no visible travel plans:

  • #86 Sphuran Industries Private Limited (Dyuti) – this team is probably not a serious entry. I will eat my hat if they turn up in Darwin.
  • #63 Alfaisal Solar Car Team – recently, they have gone rather quiet, but they have a working car.
  • #89 Estidamah – they have not responded to questions. They also might not turn up, although they have obtained several greens for compulsory documents.
  • #80 Beijing Institute of Technology – they never say much, but they always turn up in the end. I don’t expect this year to be any different.
  • #4 Antakari Solar Team – they are clearly behind schedule, but they are an experienced team. They will probably turn up. (edit: they have revealed a beautiful bullet car)
  • #55 Mines Rabat Solar Team – they seem to have run out of time. Can they finish the car and raise money for air freight? I’m not sure. (edit: it seems that they will attend the Moroccan Solar Challenge instead of WSC)
  • #98 ATN Solar Car Team and #41 Australian National University  – these teams are obviously in trouble but, being Australian, they should still turn up in Darwin with a car. (edit: both teams have since revealed cars)

World Solar Challenge late August update

In the leadup to the 2019 Bridgestone World Solar Challenge in Australia this October, most cars have been revealed (see my recently updated illustrated list of teams), and the first few international teams (#2 Michigan, #3 Vattenfall, #6 Top Dutch, #8 Agoria, and #40 Eindhoven) have arrived in Australia (see map above). Bochum (#11), Twente (#21), and Sonnenwagen Aachen (#70) are not far behind. Eindhoven (#40) are currently engaged in a slow drive north, while Top Dutch (#6) have a workshop in Port Augusta (and living quarters in Quorn).

Meanwhile, pre-race paperwork is being filled in, with Bochum (#11) and Twente (#21) almost complete. Sphuran Industries from India (#86) is not looking like a serious entrant. On a more positive note, though, Jönköping University Solar Team (#46) is revealing their car later today!

2019 World Solar Challenge: the route

Following on from my route map above for the World Solar Challenge (click to zoom), here are some personal route notes (revised from 2015 and 2017). The WSC has confirmed that the control stops are as indicated.

The graph below (click to zoom) shows approximate altitudes (taken from the Stanford 2013 elevation profile for this version of the graph). The highest point on the route (about 730 m) is 20 km north of Alice Springs, although the steepest hill (Hayes Creek Hill, summit 203 m) is about 170 km from Darwin.

Darwin – Start

Solar Team Eindhoven’s Stella starts the race in 2013 (photo: WSC)

The city of Darwin marks the start of the race.

Katherine – 322 km – Control Stop 1

En route to Katherine in 2011 (photo: UC Berkeley Solar Vehicle Team)

The town of Katherine (on the Katherine River) is a gateway to Nitmiluk National Park. It also serves the nearby Royal Australian Air Force base. The average maximum October temperature is 37.7°C.

Daly Waters – 588 km – Control Stop 2

The famous Daly Waters pub (photo: Lakeyboy)

Daly Waters is a small town with a famous pub. The Eindhoven team left a shirt there in 2015.

Dunmarra – 633 km

University of Toronto’s Blue Sky Solar team leaves the Dunmarra control stop in 2013 (photo: Blue Sky Solar)

Dunmarra once served the Overland Telegraph Line. Today it is little more than a roadhouse, motel, and caravan park. In previous races, this was a control stop.

Tennant Creek – 987 km – Control Stop 3 / End of Cruiser Stage 1

Tennant Creek (photo: Tourism NT)

Tennant Creek (population about 3,500) is a small town serving nearby mines, cattle stations, and tourist attractions. Shopping can be done at Tennant Creek IGA.

For 2019, Tennant Creek marks the end of Cruiser Stage 1. Cruisers must arrive between 14:00 and 17:00 on Monday (with penalties for arriving after 14:00). Cruiser teams will spend the night, and have the option of metered recharging between sunset and 23:00.

Karlu Karlu / Devils Marbles Conservation Reserve

Nuon Solar Team’s Nuna7 drives by the Devils Marbles in 2013 (photo: Jorrit Lousberg)

The 1,802 hectare Karlu Karlu / Devils Marbles Conservation Reserve lies along both sides of the Stuart Highway about 100 km south of Tennant Creek. It is home to a variety of reptiles and birds, including the fairy martin (Petrochelidon ariel) and the sand goanna (Varanus gouldii). Race participants, of course, don’t have time to look (unless, by chance, this is where they stop for the night).

Barrow Creek – 1,210 km – Control Stop 4

Barrow Creek Roadhouse and surrounds (photo: Adrian Kitchingman)

Barrow Creek once served the Overland Telegraph Line and nearby graziers, but is now nothing but a roadhouse. The Telegraph Station is preserved as a historical site.

Ti Tree – 1,300 km

Nuon Solar Team’s Nuna6 drives by a fire between Tennant Creek and Alice Springs in 2011 (photo: Hans Peter van Velthoven)

Ti Tree is a small settlement north of Alice Springs. Much of the local area is owned by the Anmatyerre people. In previous races, this was a control stop.

Alice Springs – 1,493 km – Control Stop 5

Alice Springs (photo: Ben Tillman)

Alice Springs is roughly the half-way point of the race.

Kulgera – 1,766 km – Control Stop 6

Sunset near Kulgera (photo: “dannebrog”)

Kulgera is a tiny settlement 20 km from the NT / SA Border. The “pub” is Kulgera’s main feature.

NT / SA Border – 1,786 km

Entering South Australia (photo: Phil Whitehouse)

The sign at the Northern Territory / South Australia border shows Sturt’s Desert Pea (Swainsona formosa), the floral emblem of the state of South Australia.

Marla – 1,945 km

Road train at Marla (photo: Ed Dunens)

Marla (population 100) has a health centre, a roadhouse/motel/supermarket complex, a police station, and a small car repair workshop. The name of the town may be a reference to the mala (Lagorchestes hirsutus) or to an Aboriginal word for “kangaroo.”

Coober Pedy – 2,178 km – Control Stop 7 / End of Cruiser Stage 2

Coober Pedy (photo: “Lodo27”)

The town of Coober Pedy is a major centre for opal mining. Because of the intense desert heat, many residents live underground.

For 2019, Coober Pedy marks the end of Cruiser Stage 2. Cruisers must arrive between 16:30 and 17:00 on Wednesday (with penalties for arriving after 16:30). Cruiser teams will spend the night, and have the option of metered recharging between sunset and 23:00.

Glendambo – 2,432 km – Control Stop 8

The Belgian team’s Indupol One leaves Glendambo control stop in 2013 (photo: Punch Powertrain Solar Team / Geert Vanden Wijngaert)

Glendambo is another small outback settlement.

Port Augusta – 2,720 km – Control Stop 9

At Port Augusta, the highway reaches the Spencer Gulf. From this point, traffic becomes much heavier, which makes life more difficult for the drivers in the race.

Adelaide – Finish

Adelaide makes quite a contrast to that lengthy stretch of desert (photo: “Orderinchaos”)

Adelaide, the “City of Churches,” is the end of the race. The official finish line marks 3,022 km from Darwin.

Cruisers must arrive between 11:30 and 14:00 on Friday (with penalties for arriving after 11:30).

American Solar Challenge 2018 Tracker Data

I just got my hands on the GPS tracker data for the American Solar Challenge last July. Out of the 13 cars from Michigan, MIT, CalSol, Western Syd, Illini, Waterloo, Minnesota, GA Tech, Poly Montreal, ETS Quebec, Bologna, W Mich, and App State, most were not being tracked during large stretches of the route (see the map above). That restricts what I can do with the data, but I will do something. Stay tuned.

Voting patterns in the United States

Because of my interest in social statistics, I’ve been exploring county-level results from the US 2016 presidential election. The map below (click to zoom) summarises the results (blue for Democrat and red for Republican, coloured according to how strongly counties voted one way or the other). Nine of the more extreme counties are highlighted.

Most of the variance in this data can be explained by demographic factors such as race, age, education levels, local unemployment, rural-urban continuum code, and median household income. The latter is particularly interesting, and the chart below provides a summary.

On a scale from −0.5 being 100% Republican to +0.5 being 100% Democrat, the curve shows the average vote of counties by 2016 median household income (where the averages are weighted by county population sizes, and LOESS smoothing is used to draw the curve). Overlaid on the diagram is a bar chart for the total population of different median household income groups (the scale for this bar chart is on the right).

It can be seen that, at the very poorest end, votes are balanced between Democrat and Republican. For example, here are the 7 poorest counties in the United States, by median household income. They are all rural:

Above that bottom end, votes trend Republican, with the peak Republican vote occurring at median household incomes around $40,000. Above about $56,000, counties swing Democrat, and the Democrat vote increases with increasing wealth. For example, here are the 4 richest counties in the United States, by median household income. They are all part of the Baltimore–Washington metropolitan area:

Essentially, the Republican Party seems to have become the party of the poor, particularly the rural poor. Indeed, the (population-weighted) median of 2016 median household incomes for Democrat-majority counties was $61,042; while for Republican-majority counties it was $52,490 ($8,552 less). For a visual perspective, the map below limits the previous one to counties with a 2016 median household income below $56,000. It is precisely because the Republican Party has become the party of the rural poor that these maps are mostly red. I had not fully appreciated this before analysing the data (although others have), but it certainly explains much of recent politics in the US. However, predicting the results of the next presidential election would require some solid demographically linked polling data as well as a good voter turnout model.

Would y’all like to see a map?

The word y’all is used as a second person plural pronoun in the United States (although in my travels I have also heard it used as a polite singular). The map above (click to zoom) shows the average frequency of use by state, according to the 2003 Harvard Dialect Survey. The usage is primarily Southern.

English needs a second person plural pronoun, it seems to me. What do all-y’all think?

Image produced using the maps package of R. Other visualisations of the survey exist.


I’m off soon to Vanuatu for a holiday. Above (click to zoom) is a map of this island nation (produced using the raster package of R, with my own colour palette). The map outlines are from (which is missing an island, unfortunately). Elevation data is from the Shuttle Radar Topography Mission (with additional void fill using a lower-resolution dataset).

The overlay in red shows light visible at night (from NASA’s Earth at Night). Apart from the two main towns of Luganville and Port Vila, the active volcanoes on Ambrym and Tanna are clearly visible (take a closer look at Ambrym’s lava lake here).

Not highlighted is the active volcano on Ambae, an island which held 4% of the nation’s population until it was recently evacuated – consider helping the evacuees via Anglican Aid.

ASC 28: Road Race Day 2 (morning)

Sunday 15 July (Nebraska time) looks like being cloudy, which is not good for the American Solar Challenge road race. The map below (click to zoom) shows the latest known team positions. GPS trackers are proving unreliable, and the grey positions reflect approximate positions as at last night. Waterloo, Onda, AppState, and the teams pictured (ETS in Ellsworth, Esteban on the road, Illini near Halsey, and CalSol in Halsey) are all on the move, however. Western Sydney seems to be back in the lead.