Thoughts filed in: Mapping


Ten rival national top cities of the world

Most countries have one city which is clearly top of the pops. In particular, one city (which may not necessarily be the national capital) is usually the largest population centre and the main economic powerhouse of a given country. Humbly presented here is a quick and not-overly-scientific list of ten countries that are an exception to this rule. That is, countries where two cities (or more!) vie neck-and-neck for the coveted top spot.

Note: all population statistics are the latest numbers on relevant country- or city-level Wikipedia pages, as of writing, and all are for the cities' metropolitan area or closest available equivalent.


Where is the official centre of Sydney?

There are several different ways of commonly identifying the "official centre point" of a city. However, there's little international consensus as to the definition of such a point, and in many countries and cities the definition is quite vague.

Most reliable and most common, is to declare a Kilometre Zero marker as a city's (and often a region's or even a country's) official centre. Also popular is the use of a central post office for this purpose. Other traditional centre points include a city's cathedral, its main railway station, its main clock tower (which may be atop the post office / cathedral / railway station), its tallest building, its central square, its seat of government, its main park, its most famous tourist landmark, or the historical spot at which the city was founded.

Satellite photo of Sydney CBD, annotated with locations of

Satellite photo of Sydney CBD, annotated with locations of "official centre" candidates.

Image source: Satellite Imaging Corp.

My home town of Sydney, Australia, is one of a number of cities worldwide that boasts most of the above landmarks, but all in different locations, and without any mandated rule as to which of them constitutes the official city centre. So, where exactly in Sydney does X mark the spot?


Australian LGA to postcode mappings with PostGIS and Intersects

For a recent project, I needed to know the LGAs (Local Government Areas) of all postcodes in Australia, and vice versa. As it turns out, there is no definitive Australia-wide list containing this data anywhere. People have been discussing the issue for some time, with no clear outcome. So, I decided to get creative.

To cut a long story short: I've produced my own list! You can download my Australian LGA postcode mappings spreadsheet from Google Docs.

If you want the full story: I imported both the LGA boundaries data and the Postal Area boundaries data from the ABS, into PostGIS, and I did an "Intersects" query on the two datasets. I exported the results of this query to CSV. Done! And all perfectly reproducible, using freely available public data sets, and using free and open-source software tools.


Current state of the Cape to Cairo Railway

In the late 19th century, the British-South-African personality Cecil Rhodes dreamed of a complete, uninterrupted railway stretching from Cape Town, South Africa, all the way to Cairo, Egypt. During Rhodes's lifetime, the railway extended as far north as modern-day Zimbabwe – which was in that era known by its colonial name Rhodesia (in honour of Rhodes, whose statesmanship and entrepreneurism made its founding possible). A railway traversing the entire north-south length of Africa was an ambitious dream, for an ambitious man.

Rhodes's dream remains unfulfilled to this day.

The famous

The famous "Rhodes Colossus", superimposed upon the present-day route of the Cape to Cairo Railway.

"The Rhodes Colossus" illustration originally from Punch magazine, Vol. 103, 10 Dec 1892; image courtesy of Wikimedia Commons. Africa satellite image courtesy of Google Earth.

Nevertheless, significant additions have been made to Africa's rail network during the interluding century; and, in fact, only a surprisingly small section of the Cape to Cairo route remains bereft of the Iron Horse's footprint.

Although both information about – (a) the historical Cape to Cairo dream; and (b) the history / current state of the route's various railway segments – abound, I was unable to find any comprehensive study of the current state of the railway in its entirety.

This article, therefore, is an endeavour to examine the current state of the full Cape to Cairo Railway. As part of this study, I've prepared a detailed map of the route, which marks in-service sections, abandoned sections, and missing sections. The map has been generated from a series of KML files, which I've made publicly available on GitHub, and for which I welcome contributions in the form of corrections / tweaks to the route.


Natural disaster risk levels of the world's largest cities

Every now and again, Mother Nature reminds us that despite all of our modern technological and cultural progress, we remain mere mortals, vulnerable as always to her wrath. Human lives and human infrastructure continue to regularly fall victim to natural disasters such as floods, storms, fires, earthquakes, tsunamis, and droughts. At times, these catastrophes can even strike indiscriminately at our largest and most heavily-populated cities, including where we least expect them.

This article is a listing and an analysis of the world's largest cities (those with a population exceeding 10 million), and of their natural disaster risk level in a variety of categories. My list includes 23 cities, which represent a combined population of approximately 380 million people. That's roughly 5% of the world's population. Listing and population figures based on Wikipedia's list of metropolitan areas by population.


Kosher and the Land that G-d forgot

Per the laws of kashrut, the Jewish religion prohibits the consumption of meat from many animals and birds. Islam's laws of halal enact very similar prohibitions.

Australia and New Zealand are two countries located very far from the Middle East, the home of Judaism and Islam. Their native wildlife is completely different to that found anywhere else in the world. Of course, since European settlement began, they've been thoroughly introduced to the fauna of the wider world. Indeed, these two countries are today famous for being home to some of the world's largest sheep and cattle populations.

However, let's put aside the present-day situation for now, and take ourselves back in time a thousand or so years. Artificial transcontinental animal transportation has not yet begun. The world's animals still live in the regions that G-d ordained for them to live in. G-d has peppered almost every corner of the globe with at least some variety of kosher birds and mammals. Every major world region, bar one.

My fellow Aussies and Kiwis, I'm afraid the verdict is clear: we are living in the Land that G-d forgot.


Highway border crossings between Chile and Argentina

I've spent a fair bit of time, on several occasions, travelling in South America, including in Chile and Argentina. I've crossed the land border between these two countries several times, in several different places. It's an extremely long border, measuring 5,308km in total.

Recently, I was looking for a list of all the official crossings between the two countries. Finding such a list, in clear and authoritative form, proved more difficult than I expected. Hence, one thing led to another; and before I knew it, I'd embarked upon a serious research mission to develop such a list myself. So, here it is — a list of all highway border crossings between Chile and Argentina, that are open to the general public.


Boycott GPS

In the developed world, with its developed mapping providers and its developed satellite coverage, GPS is becoming ever more popular amongst automobile drivers. This is happening to the extent that I often wonder if the whole world is now running on autopilot. "In two hundred metres, take the second exit at the roundabout, then take the third left." Call me a luddite and a dinosaur if you must, all ye GPS faithful… but I refuse to use a GPS. I really can't stand the things. They're annoying to listen to. I can usually find a route just fine without them. And using them makes you navigationally illiterate. Join me in boycotting GPS!


Non-Shelbyville Sydney map

A work colleague of mine recently made a colourful remark to someone. "You live in [boring outer suburb]?", she gasped. "That's so Shelbyville!" Interesting term, "Shelbyville". Otherwise known as "the 'burbs", or "not where the hip-hop folks live". Got me thinking. Where in Sydney is a trendy place for young 20-somethings to live, and where is Shelbyville?

I've lived in Sydney all my life. I've almost always lived quite squarely in Shelbyville myself. However, since the age of 18, I've gotten to know most of the popular nightlife haunts pretty well. And since entering the world of student share-houses, I've also become pretty familiar with the city's accommodation hotspots. So, having this background, and being a fan of online mapping funkiness, I decided to sit down and make a map of the trendiest spots in Sydney to live and play.

Map of non-Shelbyville Sydney

Map of non-Shelbyville Sydney


Haiti coverage in OpenStreetMap vs Google Maps

I was recently reading about how OpenStreetMap has been helping the Haiti relief effort, in the wake of the devastating earthquake that hit Haiti's capital back in January. Being one of the poorest and least developed countries in the world, Haiti's map coverage is very poor. However, a group of volunteers have radically changed that, and this has directly helped the aid effort on the ground in Haiti.

To see just how effective this volunteer mapping effort has been, I decided to do a quick visual comparison experiment. As of today, here's what downtown Port-au-Prince looks like in Google Maps:

Port-au-Prince in Google Maps

Port-au-Prince in Google Maps

And here it is in OpenStreetMap:

Port-au-Prince in OpenStreetMap

Port-au-Prince in OpenStreetMap