X Percent of the Population of Scotland Lives Within Y Miles of Edinburgh

Follow up from the Glasgow post by request.

This is a pretty easy question to answer, using the 2011 Scottish Census population results and the Census Output Area Population Weighted Centroids. Then we get the extents of Edinburgh City Council from OS Boundary Line.

The results are:

Pop. Count: %
Scotland 5295403 100
Edinburgh 476626 9
25 km 1276757 24.1
50 km 2500093 47.2
50 miles 3919910 74
100 km 4310869 81.4
100 miles 4812421 90.9

So we see more than people live close to Glasgow, but with 50 miles + they are closer to the capital.

To see how these boundaries look on a map:

Population buffers around Edinburgh

A few caveats:
We are using the population weighted centroids, which will produce some minor inaccuracies, but is a very good generalisation.
Also we are using euclidean buffers on the British National Grid plain, so these are not geodesic buffers. The difference will likely be small at these distances.

Mapvember 2014

Mapvember: A map/tutorial a day for every day in November.

Some days had more than one map, some had tutorials, one just had a photo. Some were very easy, others would have take a couple of days of work.

Excellent experience, good learning experience and an opportunity to post previous projects that were a bit short of being great. A little time consuming at times though. I started making the maps around half way through October, so I had almost the first week ready when November began, but the days ticked by quickly. Happy to have done it. I encourage everyone to join in next year, or any other month.

Visitor Statistics:

Total views: 3047
Uniques: 2289
Pageviews: 4327

Top 10 Countries:

Country Visitors
United Kingdom 1147
United States 363
Germany 183
France 120
Canada 85
Italy 67
Spain 66
Australia 56
Switzerland 42
India 39

Mapvember Countries

Top 10 Cities:

City Visitors
Glasgow 340
London 212
Edinburgh 122
Rostock 45
Aberdeen 42
Stirling 35
San Jose 31
Vienna 28
Berlin 28
Zagreb 26

Mapvember Cities

Other Months:
August Visitors: 303
September Visitors: 641
October Visitors: 523
November Visitors: 3047


Total AdSense earnings: £1.87

Which actually covers my servers costs. So break even!

Most popular posts:


Site Visitors
Reddit.com 747
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Twitter 122
GIS.StackExchange.com 71
Facebook 70
Flickr 15

Top SubReddits:

SubReddit Visitors
/r/glasgow 200
/r/scotland 120
/r/london/ 46
/r/gis 19
/r/QGIS/ 4

Thanks for visiting.

Great Circle Flight Lines in PostGIS

There is an excellent post by Anita Graser about creating Great Circles in PostGIS.

However as of PostGIS version 2.1 this can be done in a different (better) way, using the geography functions.

PostGIS Great Circles

For more information about geography, see:
Introduction to PostGIS – Geography

This allows us to create the great circles without having to add in a new projection.

So we first need to create our three tables in PostGIS:

The data itself can be found at: openflights.org/data.html

We can then load our data through PGAdminIII. You can just right click on a table and select import. Remember to not load the “uid” column, because it is our primary key which will be populated automatically and not in the original data. You will also want to define it as the primary key.

Now we need a geometry column in the airports dataset.

We can define our geometry in the airports dataset from the Latitude and Longitude columns.

And create a spatial index.

Then we can create a flights table.

This table will have a source geometry and a destination geometry along with a few other attributes. I added a primary key to this table as well.

To filter out a specific airport, for example Honolulu we use the “Airport ID”.

Then we add in the actual line geometry column.

And populating the great circle geomtrey:

This is works great to an extent, but QGIS still has some trouble with lines that cross the date-line.


We can fix this using a Pacific centered projection like EPSG:3832.


We can either set QGIS to the projection. Or we could have set our geometry the this projection initially when creating the flight lines.

Thanks to:
The World Is A Village – PostGIS: using latitude and longitude to create geometry

Helsinki Airport the Gateway to the East

The shortest route between two points on the earth is a great circle. This is a straight line on a globe, but ultimately looks like half-circle when projected.

Due to Helsinki Airports location, it is an ideal hub for East Asia travel. Starting at practically any European city and travelling to Far East Asia via Helsinki. The final route will almost be a straight line.

Helsinki Flights

Population of Scotland Mapped

One random point on the map for each person within a postcode in Scotland.

OS Code-Point Open points.
Voronoi polygons from the postcodes.
Join 2011 Scottish Census postcode population counts to Voronoi polygons.
Clip the resulting polygons to the Scottish coastline (using PostGIS for time saving).
Intersect the lakes out of the resulting polygons.
Random point in polygon into the postcode Voronoi polygons (minus lakes), using the census counts.

Population of Scotland Mapped

An easier approach would have been to use the NRS supplied postcode areas for Scotland mentioned in previous posts. A better display of this data would be through a web mapping environment, which is working on my home environment but lacking hosting.