Category Archives: Google Maps

Visualising data on Cambridgeshire council wards with Carto

“Data is the new oil…” is a phrase often used by those in the industry to describe the vast,  valuable and extremely powerful resource available to us. We generate an astronomical amount of data, in fact 90% of the data in the world today has been created in the last two years alone according to IBM. However, there is a real skills gap when it comes to working with the data – people often perceive it as being too complicated or intimidating to work with, while those who can extract it, process it and refine it will reap the rewards.

Data is readily available if you know where to look for it. The UK Government’s site opens up datasets on the environment, health and education and often these datasets come cleansed without the need to process it too much (though I would always advise the cleansing and scrutiny of data regardless of source!). As a Cambridgeshire resident, I am very lucky to have access to Cambridgeshire Insight Open Data, which is a repository of open data relating to local matters and is managed by Cambridgeshire County Council and run by a local partnership. I therefore wanted to have a go at playing around with the data and utilising the numerous free tools available to explore and visualise it with the hope of making it more accessible – let’s face it, there’s more to life than staring at a spreadsheet!

My first project will be looking at crime figures in the county and projecting them on to a map, by council ward, using an online tool called Carto. The data will be sourced from the Cambridgeshire Crime Rates and Counts 2015/16 data set on the Cambridgeshire Insight Open Data site and I will be focusing on the data related to the rate of crimes per 1,000 population at ward and district level. The data I’m using can be found in column “CU” in the Excel sheet.

The benefit of looking at the rate instead of raw numbers is that it means the stats aren’t skewed by heavily populated areas e.g. I would expect the number of crimes in heavily populated areas to be higher than those in remote rural communities, but as the rate takes in to account the population within the area, it provides a more accurate measure.

The mapping processes behind Carto aren’t sophisticated enough to recognise a council ward name in data (yet), but it does allow you to overlay KML data meaning that the wards can be “drawn” on to the map in a new layer. Where does this KML data come from? Surely we don’t have to create it ourselves? Heh, don’t be silly, someone has already done all of the hard work for us (phew!) – thank you to Alasdair Rae, a Lecturer in the Department of Town and Regional Planning at the University of Sheffield who created it for an article in the Guardian and a spreadsheet containing all of the KML shapes of all council wards in England can be downloaded via a Google Fusion table.

I then matched up the wards, by name, between the two sheets and pulled out the KML code for each one and the resulting sheet can be found here. From here, everything can be done from within Carto so create yourself a free account and prepare to be dazzled!

There are plenty of Carto tutorials but there are essentially two sides to the tool: the dataset side (where the data can be uploaded) and the mapping side (where the maps connect to your existing datasets). The great thing about Carto is that your maps can be embedded in your own website so hey presto, here’s the resulting map…

Total crime rate per 1,000 people by Cambridgeshire ward (2015/2016)

Source: Cambridgeshire Insight Open Data :: Full page view of the map

I hope to make this a regular series of small tutorials about data visualisation and the use of open data so check back in a few months to see what else I have been up to!

Disclaimer: I am employed by Cambridgeshire County Council, though I have no links with the Insight Open Data team.

Quick links

Using a UK postcode to find Lat and Long and other useful information

So I have a list of UK postcodes and I want to find out the latitude and longitude of that postcode to plot it on to a map. There are numerous ways to do this, including:

1. Visiting Google Maps

2. Entering the postcode in to the search box

3. Right-clicking on the little point on the map and selecting “What’s here?”

4. Copying and pasting the lat and long that magically appears in the search box.

That’s nice, quick and easy BUT what if I’ve got hundreds or thousands of postcodes to search? I can’t spend the whole sunny weekend doing the same procedure can I?


I’m self-learning Tableau at the moment and it seems to have great location support…if you provide it with US addresses (gnrrr), but I wanted to find a way of plotting a series of points on a map of the UK derived using their addresses. A bit of Google searching led me to UK Postcodes (set up by Stuart Harrison and based on Ordnance Survey OpenData) , a site that lets you enter a UK postcode and returns lots of information about that location (e.g. long, lat, county and right down to district and ward) and what made me excited was that the site had an API allowing you to pass it a postcode via URL (e.g. and it would output the meta data it in either XML, CSV, JSON or RDF for you. PERFECT!

After a further read around the site, I found that Edd Robinson had created a library acting as a wrapper for the API which I could import in to my own Python project. And so, without further ado here is my Python code:

[code language=”Python”]
from postcodes import PostCoder
import csv

f = open(‘Extracted_Data_from_Postcodes.csv’, ‘w’)
i = 0
pc = PostCoder()

loc_lat = ""
loc_long = ""

with open(‘Postcodes_to_Extract.csv’, ‘rU’) as g:
reader = csv.reader(g)

for row in reader:
#Col 0 = ID :: Col 1 = Postcode
result = pc.get(str(row[1]))

if str(result) != "None":
location = result[‘geo’]

for key, value in location.items():
if (key == "lat"):
loc_lat = value
if (key == "lng"):
loc_long = value

#ID, Postcode, Lat, Long
write_to_file = str(row[0]) + ", " + str(row[1]) + ", " + str(loc_lat) + ", " + str(loc_long) + "n"

#Add the iteration count to output to screen to see how far we are up to.
print str(i + 1) + ", " + write_to_file
#If there is a problem translating the postcode, output "BROKEN" to file to manually check.
write_to_file = "BROKEN, " + str(result) + ", " + str(row[0]) + ", " + str(row[1]) + "n"

print str(i + 1) + ", BROKEN, " + str(row[0]) + ", " + str(row[1])
i = i + 1



My input file looked like this:

109484, SG5 4PF
109486, MK44 2DB
109487, LU4 9UJ
109488, LU6 1RE
109489, MK43 8DY
109490, MK45 5JH
109491, MK44 3QD
109492, MK45 3BX
109493, MK17 9QL
109494, MK43 9JT

And my screen output looked like this:

1, BROKEN, 109484, SG5 4PF
2, 109486, MK44 2DB, 52.214741, -0.461977
3, 109487, LU4 9UJ, 51.927696, -0.500824
4, 109488, LU6 1RE, 51.879322, -0.563452
5, 109489, MK43 8DY, 52.164539, -0.623209
6, 109490, MK45 5JH, 51.982376, -0.495111
7, 109491, MK44 3QD, 52.137440, -0.377085
8, 109492, MK45 3BX, 52.080341, -0.446214
9, 109493, MK17 9QL, 51.989906, -0.619803
10, 109494, MK43 9JT, 52.095955, -0.528752

Afterwards, I was then able to manually check out why SG5 4PF failed, actually, I’m not sure why it failed but I was able to correct the lat & long via a Google Map search. Exactly what I needed with minimal effort and a chance to flex my muscles with Python again. I then imported the CSV in to Tableau, but that’s the subject of a future blog post…

Displaying English districts in Google Earth

The other day at work, I was asked to find out how many X* were in a particular district in England. Given we seem to have SO MANY ways that we slice & dice the country up with Ceremonial Counties, Parliamentary Constituencies, Local Government Districts (which can be boroughs, cities or Royal Boroughs) you can see why I started to have a small panic! But then I remembered you could search for districts in Google and it would outline them with a little red boundary line, so I gave it go.

“Woking District”

Woking Outline

Ta dahhhh!

Great…except I then wanted to overlay the data I already had mapped in a Google Fusion table with longitudes & latitudes. FAIL. I could find no way of either exporting this boundary data, or overlaying the longitude & latitude points I had setup in a fusion table. So I Googled around the subject and found this wonderful post on Stack Overflow – so I needed to head on over the OpenStreetMap, download the boundary data for my district, additionally convert the gpx file to a KML and then whack it in to Google Earth…so I did that!

1) Find the district you want in OpenStreetMap

2)  Download the gpx file and then convert it to a KML on

3) Load your resulting KML in to Google Earth and hey presto…

Google Earth - Woking

I then exported my data with the longitude & latitude points in it from my Google Fusion table as a KML file and then imported it in to Google Earth and all the little points appear on a layer over my district boundary.

Woking Schools - Google Earth

Hooray! Fortunately, there were only four points within the boundary – I need to think about what would happen if we were talking hundreds or thousands – how would I manage that? Is there a way to filter in Google Earth to say give me all the X in boundary Y? I’m not sure but I’ll be darn sure to find out!

* Trying to maintain a bit of anonymity here!