Author Archives: Heikki Vesanto

John Snow Pub

I was once at an OpenStreetMap conference where 6 out of the 8 talks in one day had an image of the John Snow Cholera Map. And no surprise, it is an excellent, relatable, and interesting early example of GIS. The spatial relationship is unmistakable.

Original map overlaid on modern day London:

The site of the Broad Pump is now the location of a pub called the “John Snow”, which is well worth a visit if you are in London.

John Snow location:

John Snow Pub
Sign with blue plaque
Blue plaque
Pump without handle memorial

Every Person in Great Britain Mapped

A follow up to my previous post: Every Person in Scotland on the Map. Winner of the 2016 OS OpenData Award for Excellence in the use of OpenData from the British Cartographic Society.

Full size interactive map.

The mapping process is pretty straightforward, and not accurate. I don’t know where you live. But I can make an educated guess.

I simply amalgamate the two sets of census data from the NRS (National Records of Scotland) for Scotland (2011 census) and the ONS (Office of National Statistics) for England and Wales (2010 census).

Postcodes were then created based on the ONS Postcode Directory, filtering for postcodes that were live in 2011 (which is the latest census data). The postcode centroids were turned into polygons using voronoi polygons.

Then we simply select all of the buildings in a postcode from Ordnance SurveyOpen Map product, filtering out most schools and hospitals. Then we put a random point in a random building for each person in that postcode.

I would have loved to include Northern Ireland, but the Ordnance Survey of Northern Ireland do not have an equivalent open building outline dataset, like Open Map from the Ordnance Survey.

Rendered with: QGIS tile writer python script. Processing done 100% in PostGIS.

Struve Geodetic Arc

The Struve Geodetic Arc is a chain of triangulation stretching more or less down the 26° E line of longitude from near Hammerfest on the Arctic Ocean over 2,820 km south to Izmail on the Black Sea. The survey was carried out between 1816 and 1855 under the guidance of F.G.W. Struve.

Theoretically, a degree of latitude is a constant and would have the same value at the equator as at the pole. But already Isaac Newton believed that the Earth was slightly flattened at the poles. This question of the shape and size of the Earth inspired the astronomer Friedrich George Wilhern Struve to come up with his famous Meridian Arc measurement.

The scheme included 258 main triangles with 265 not and over 60 subsidiary station points.The selection of points involves a total of 34 sites on the Struve Geodetic Arc. In today’s geography. the Arc passes through ten countries, viz. Norway (4 station points), Sweden (4), Finland (6), the Russian Federation (2), Estonia (3). Latvia (2). Lithuania (3). Belarus (5), the Republic of Moldova (1), and Ukraine (4).

All of the points in the Arc were designated as UNESCO World Heritage sites in 2005.

The site at Puolakka is easily accessible from central Finland, for example from Tampere, or especially Jyväskylä.

There is parking at the start of the walk, which is not maintained during the winter. But there is ample space on the roadside for parking. The path itself was in good condition but the road to the start could be difficult after a heavy snowfall.

The walk itself is 1km, all uphill. The path is very well maintained with stairs for the steeper sections. The view is definitely worth the time to visit.

Beginning of the walk.
740 meters to the start and 260 to the lookout tower
Stairs on the path
Lookout tower
Triangulation pillar at the top
View from the tower
View from the tower
Info board at the start of the walk
Path map

Walk path: