In honour of the bicentenary of John Snow’s birth – and because I was asked to by someone via email – I have now released my digitisation of John Snow’s Cholera data in a few other formats: KML and as Google Fusion Tables. To save you reading my previous blog posts on the subject, I’ll […]
Updated 6th Jan 2020: This post has been updated to fix the code example and the link to the Landsat shapefile download. As part of some work I was doing for my PhD, I needed to automatically find what Landsat scene path and row would contain a pixel with a certain latitude/longitude co-ordinate (this was […]
The New Year is a time of new beginnings – and so it is rather appropriate to launch the complete redesign of my Free GIS Data list today. As you can see from the screenshot above, it looks far nicer than before – but it is also far easier to navigate. The dropdown […]
So, I’ve been pondering an interesting scientific dilemma recently: how do you validate a validation technique? That is, if you’re using a certain procedure to validate some data (that is, check how correct/accurate it is), how can you validate the validation procedure itself? This has come up in my work recently in relation to validating […]
A while back I released a GIS dataset containing Snow’s Cholera analysis data in modern GIS formats, and georeferenced to the British National Grid (see my previous post). Unfortunately, there was an error in some of the attributes of the Cholera Deaths shapefile which caused issues when using the data. This error has now been […]
I’ve just signed the Science Code Manifesto because I firmly believe in what it says. Ok well, that probably doesn’t tell you much – generally I tend to believe in things that I sign – but I’d like to tell you why I signed it, and why I think it’s really important. A lot of […]
As you might know from some of my previous posts, I’m a big fan of making my scientific work reproducible. My main reasons for being so keen on this are: Reproducibility is key to science – if it can’t be reproduced then it can not be verified (that is, the experiment can’t be tried again to […]
While processing some data at work today I had an issue where I had a raster dataset in ArcGIS, where all cells with invalid data had been set to 9999. Of course, this caused a lot of issues for the statistics on the dataset – basically they were all nonsense – so I needed to […]
In 1854 there was a massive cholera outbreak in Soho, London – in three days over 120 people died from the disease. Famously, John Snow plotted the locations of the deaths on a map and found they clustered around a pump in Broad Street – he suggested that the pump be taken out of service […]
When you try and reproject a dataset in ArcGIS (for example, by using the Project Raster tool) you will see a dialog a bit like the one below: The highlighted field wants you to specific a Geographic Tranformation. Although it says that it is optional, it often isn’t (I think the optionality depends on the type […]