Ireland’s Population by Altitude

I read Alasdair Rae’s very interesting post where he created a graph of Great Britain’s population by altitude. Using WorldPop data and the EU DEM I used QGIS, Seaborn and Inkscape to create the following graph for Ireland. I must do a bit of digging to see whether the 400 – 500 metre slight bump can be explained by a discrete area…

 

Horizontal bar plot showing Ireland's population by altitude

Horizontal bar plot showing Ireland’s population by altitude

Camino de Santiago

I was talking to someone recently about the Camino de Santiago and whether it plays a role in sustaining the population of the provinces it traverses. It’s a rainy Sunday here so I sat down with a cup of coffee and decided to create a population density map using data from: OSM, WorldPop, Natural Earth and Peter Rukavina’s website ruk.ca.

It proved quite difficult to get GIS data on the route of the Camino through Spain. I first downloaded the Spain.osm.pbf file from Geofabrik and filtered it using Osmium however no matter what combination of tags and names etc. I used, I couldn’t get more than a few thousand disjointed lines that were not fit for purpose. I then found Peter’s website where he had the route as a geojson that I could easily use. I then spent some time in QGIS making the below map. I purposefully didn’t use the minimum and maximum numbers in the legend as I didn’t think it would add much value instead I used low to high.

I also haven’t marked that it’s technically the Camino Francés as it’s the most popular route.

To answer the population question, I buffered the route by 5km and counted the number of people that live within this area. It worked out at 1,316,141 or 2.77% of Spain’s population, I was surprised, I thought the figure would be significantly larger.

Camino de Santiago Population Density

Camino de Santiago Population Density

Knockanore Hill

I was home recently and drove up to the top of Knockanore, a hill just outside Ballybunion, Co. Kerry. Its elevation is 267m and is by far the highest hill in this part of North- Kerry. This got me curious — how much of Kerry is greater or less than this elevation? Below is a quick map I put together from the EU-DEM courtesy of the European Environmental Agency. It turns out 267m is higher than 82.7% of the county, interesting. There’s a story that does the rounds colloquially in North Kerry that, on a clear day, it’s possible to see five counties from this elevation. If I’ve time in the next few weeks I’d like to create a viewshed to test this.

 

Knockanore, Co. Kerry, Ireland

Knockanore, Co. Kerry, Ireland

 

Knockanore, Co. Kerry, Ireland

Knockanore, Co. Kerry, Ireland

Birthplaces of Irish Taoisigh

I made a quick map during the week of the birthplaces of Irish Taoisigh. The below gives a quick overview however I thought putting a cartogram together also might below. No surprise to see Dublin has the most. I know we’re a young country but I found it interesting the number of counties that haven’t had a Taoiseach.

 

Birthplaces of Irish Taoisigh

Birthplaces of Irish Taoisigh

Cartogram - Birthplaces of Irish Taoisigh

Cartogram – Birthplaces of Irish Taoisigh

 

Over the Horizon

I recently moved to the south-west of Western Australia, close to a town called Busselton. The town is famous for, among other things, the longest timber-piled jetty in the Southern Hemisphere (at 1,841m). The first time I walked the jetty I stood at the end and gazed out wondering if I could follow my gaze in a straight line where would it make landfall?

Busselton Jetty

Busselton Jetty

The End of the Jetty

The End of the Jetty

THEORY

To answer the question accurately there are two concepts worth noting. The first is that of a rhumb line — if I digitised a line (in a projected coordinate system) representing the jetty and extended that angle, it would result in a rhumb line which at the intersect point would be off to the order of a couple of hundred kilometres.

Rhumb Line

Alvesgaspar – CC BY-SA 2.5 (https://creativecommons.org/licenses/by-sa/2.5) via Wikimedia Commons

The shortest distance between any two points on the surface of the earth is the minor arc of a great circle. So if I was standing where the signpost is shown above, that is in the centre of the end of the jetty, I would need to create the minor arc of a great circle line. This would be, as the great circle wiki article states ‘analogous to “straight lines” in Euclidean geometry‘.

Minor Arc of Great Circle

CheCheDaWaff – CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0) via Wikimedia Commons

CREATION OF THE LINE

The process I followed to create the line was as follows:

  1. Create two points at the end of the jetty to represent the angle looking out.
  2. Create a line between the two points.
  3. Calculate the angle of the line and extend it for 1/4 the circumference of the earth at the equator.

The below GIF visualises the process-

Creation of Line

Creation of Line.

If you’d like to carry out the same analysis yourself below is the SQL code. I’d like to thank Darrell Fuhriman for his help.

-- assume two points, calculate the angle, then extend it.
-- point 1 = -33.6307920509579, 115.338797474435  
-- point 2 = -33.6290969607648, 115.338316140276 
 SELECT
ST_Segmentize( -- break it up into segments so it looks better when re-projecting for display
    ST_MakeLine(
        ST_SetSRID(ST_Point(115.338797474435, -33.6307920509579), 4326) -- starting point (ST_MakeLine expects projected coordinates)
        ,ST_Transform(
      	ST_Project( -- find a point a long way away to use  as the second point in the line
                ST_Point(115.338797474435, -33.6307920509579)::geography -- starting point again
                ,10000000 -- 1/4 circumference of earth at the equator (should get us far enough)
                ,ST_Azimuth(ST_Point(115.338797474435, -33.6307920509579)::geography, ST_Point(115.338316140276, -33.6290969607648)::geography) -- angle between my two points
            )::geometry,
        4326)
    )::geography
,20000 -- break it into segments of 20km
);

RESULT

An imaginary line from the end of the jetty travels 802km before intersecting with Tamala, WA. It then travels for another 2,127km before meeting the district of Ayah in the Kebumen Regency in the province of Central Java, Indonesia. Where it meets land is almost equidistant between the towns of Kebasen and Kebumen (the latterhad a population of 131,750 based on the 2020 census [source]).

Busselton Jetty Line

Busselton Jetty Line

Jetty Line on a Globe

Jetty Line on a Globe

If you’re taken by the above and you ever want to travel to where it touches land in Indonesia, the coordinates are: -7.7628936, 109.4018789.

Halloween Map – Castles of Europe

For Halloween this year I wanted to create a spooky, atmospheric map. I settled on mapping the castles of Europe including Bran Castle. I know that Bran Castle doesn’t actually have any historical links to Bram Stoker but I thought it would be nice to include given it’s reputation. I came across a great website called https://download.osmdata.xyz/. It allowed me to easily download a geopackage of all the historic tags from OSM.

Now the the elephant in the room — the actual castle data. I filtered the data by historic=castle. I has tried filtering it by categories such as castle_type but there just wasn’t enough tagged to make a nice map. People commenting on Reddit have been at pains to point out how inaccurate the map is and by and large they are correct. It’s the best that could be make with the data available and I usually wouldn’t publish something where I know the data wasn’t up to scratch however as this was only meant to be a fun Halloween map I thought an exception could be made!

Anyway, I hope you enjoy it (above data caveat aside) as much as I enjoyed making it. Happy Halloween!

Castles of Europe

Castles of Europe

Australia – Place Names Ending in ‘UP’

I was having a chat at work recently about the place names in Australia that end in ‘up’. It comes from a dialect of the Noongar Aboriginal language of Australia and means ‘place of’. Below are two quick maps I put together. You can clearly see the concentration in the Noongar region of South-West Western Australia.

Place Names Ending in 'Up'

Place Names Ending in ‘Up’ – Australia

Place Names Ending in 'UP'

Place Names Ending in ‘UP’ – South West, Western Australia

Ireland – Densest 1km² per County

I’ve been writing a lot about population density at the moment and it got me thinking about density in Ireland. We all know we’re pitiful in terms of other European countries and we know from census 2016 that we’re sitting at 70 persons per km². What I’m curious about is what’s the densest square kilometre in each county?

It is import to note that the densest square kilometre in each county below is the densest square kilometre from a predefined 1km² grid for the entire country which is manifestly different from the true densest square kilometre in each county but it’s the best data I have access to as a member of the public. If you want to read more about this issue it’s called the modifiable areal unit problem. A simple image to explain this is show below. From a predefined grid that’s draped over the country we can see that cell 3 would be the most dense 1km² however if a cell was placed where cell 5 is we can see that it would be densest 1km² by a large amount, that in a nutshell is the MAUP problem.

Grid Shortcomings

Grid Shortcomings

 

I used the ’16 census data to generate the below maps to answer the question for each county. What clearly stands out for me is that for a lot of counties it’s housing estates that make up the densest square kilometre. Hopefully with Project Ireland 2040 now in place we can start to do better and go towards sustainable densities throughout the country.

Carlow

1. Carlow

Hyperlinks to maps for each of the other counties:

  1. Carlow
  2. Cavan
  3. Clare
  4. Cork
  5. Donegal
  6. Dublin
  7. Galway
  8. Kerry
  9. Kildare
  10. Kilkenny
  11. Laois
  12. Leitrim
  13. Limerick
  14. Longford
  15. Louth
  16. Mayo
  17. Meath
  18. Monaghan
  19. Offaly
  20. Roscommon
  21. Sligo
  22. Tipperary
  23. Waterford
  24. Westmeath
  25. Wexford
  26. Wicklow

I realised with the above images that I forgot to include part of the label that showed where in each county the location was. Below are the same maps as above but they now include the location and the lat, long for each square kilometre. Maybe both versions can be used for a very nerdy quiz??

  1. Carlow
  2. Cavan
  3. Clare
  4. Cork
  5. Donegal
  6. Dublin
  7. Galway
  8. Kerry
  9. Kildare
  10. Kilkenny
  11. Laois
  12. Leitrim
  13. Limerick
  14. Longford
  15. Louth
  16. Mayo
  17. Meath
  18. Monaghan
  19. Offaly
  20. Roscommon
  21. Sligo
  22. Tipperary
  23. Waterford
  24. Westmeath
  25. Wexford
  26. Wicklow