**On Tuesday 2nd of August I gave a short talk to the crowd at the London Missing Maps Mapathon about my experiences of being a validator. I had a scruffy piece of paper with some bullet points scribbled on it so this is my attempt to translate some of what I said that evening into a post.**

It feels pretty special to be standing up here tonight. In August two years ago (2014) I came along to my first mapathon with no experience of HOT, OSM, or any of the tools we’ve been using tonight: ID editor or JOSM. I started mapping with tracing lots of buildings, like tonight’s task, but in Sierra Leone and Liberia. This was at the time of the Ebola outbreak in West Africa and there was a lot of mapping to be done.

I started mapping with ID editor but after a couple of months I saw people near me using JOSM and was interested enough to download it and try it out at the mapathons. There was lots of help around and as I got comfortable using JOSM I got asked whether I’d consider doing some validation too. And I, perhaps foolishly, said I’d give it a go.

So how does validation fit into Missing Maps? Well, first off validators are volunteers too. If you’ve been to the Missing Maps website you will have seen this graphic showing the steps in the process starting with remote mappers, it then getting added to by community volunteers, and the third step where the data is used by humanitarian organisations. Validation is part of the remote mapping process, we’re very much a part of what is going on tonight.

The validation is there to provide a second pair of eyes and improve confidence of the end users in the whole process.

So what we actually do? It’s everything from looking to see all the buildings in a square are mapped and the roads labelled correctly to sense-checking the work on a square level and also a regional level. As we have already seen quite a few squares in different countries we’re aware through hard experience of some of the pitfalls in mapping.

Looking back I’m pretty confident that I have mapped stationary vehicles as buildings in the past… And as an ID editor user I was always relieved by the thought that someone else would be looking at my work and catch any major mistakes. The role of a validator is not a punitive one! We can offer some advice if needed, but by and large we’re just so grateful that you are mapping. There is so much territory that needs still to be covered.

The data that we are producing needs to be fit-for-purpose rather than perfect. It needs to be useable by the people on the ground using it, so we do look at consistency in the data across a region, but there will still be room for improvement work from the ground.

I guess I’m trying to talk here about why I’m still mapping and validating two years on. Dr John Snow often gets mentioned at these evenings (and if you haven’t heard of him do look him up), but I’d like to add someone else to the mix. Octavia Hill is a personal hero of mine and 34 years after Snow’s cholera map she was mapping green spaces as a part of a campaign for clean air and access rights to healthier spaces for poorer people in London. So I know mapping has been an effective tool in the past.

As I mentioned earlier I started mapping during the Ebola crisis. I did find that quite overwhelming at the time: the need was so huge. It was great to support the work and HOT do such a tremendous job of supporting in situations like that. It was really something to be part of that too. But for me it has also showed the value of the vision of Missing Maps to try and map areas before the next situation arises so that this support will already be there. It’s great to contribute my skills to a long lasting project too as all these maps are available in OSM.

We do need more validators though. As you can see from the graphs the green section of the validated areas do lag behind all the mapping. It’s a hugely supportive community we’ve got here: I’d like to thank Nick and Ralph in particular for all the help you’ve given me so far. (I’ve asked about a million questions so far and I’ve got another million to go no doubt.) And you can join us too.

I’d encourage you all to keep mapping those squares and getting familiar with the tools we use. Ask questions, come sit next to us and see what we do, give it a go. We need everyone’s input though so thank you so much for all the mapping you all already do!