A while back I compared three sites that crowdsource data about the natural world: the RSPB’s Big Garden Birdwatch, NatureLocator’s Leaf Watch and the UK snow map. I return to these sites and consider another aspect: geographical unevenness.

(Leaf Watch has I think ended but other NatureLocator surveys have been running and the same principles apply to them).

All these sites ask people to submit information about what is visible around them. So you are likely to get more reports from where there are many people, such as big cities and fewer from sparsely inhabited areas such as the Highlands or mid-Wales.

For the snow map this may not matter too much. It’s clear there are people in remote areas sending in reports, which appear as dots or flakes on the map. There are some in the ‘cefn gwlad’ behind Aberystwyth as I write. And there appears to be a limit on how many dots can appear in the same small area. Nevertheless, snowfall in London generates a busier looking map than snowfall in the countryside. But the snow map is not a matter of record; it is ephemeral and serves to inform people right now about where snow is falling so they can plan journeys/get the sledge out/feel Schadenfreude. So, when looking at it, it just needs a little thought and a mental map of major centres of population to factor out the weighting towards cities.

The Big Garden Birdwatch does not attempt to cover the country evenly. It’s expected that the birdwatching will take place in gardens (hence the name) or public parks, and the survey is specifically intended to measure avian activity near human settlements. (This will cause variations, for example due to hard weather in some years which will drive birds from open country into gardens. There are further sources of bias, for example caused by one species of bird being mistaken for another and by less conspicuous species such as wrens being undercounted. And being in January summer visitors will be missed altogether. But that’s going beyond the scope of this post.)

NatureLocator is a scientific project which was driven by biologists needing data. Although it was produced by colleagues, I haven’t been involved enough to know what exactly is done with the information submitted. Since what was being measured was the overall distribution of leaf miner moth infestation and the proportion of trees affected, the main risk due to geographical unevenness is not getting enough reports in some areas. There might also be a bias due to users being more likely to report the presence of the moth than its absence. The results are summarised here where the geographical issue is acknowledged.

I’ve been using three sites which crowdsource information about the natural world and put it out again:

• Leaf Watch (Disclaimer: this was developed by some colleagues) Collects data submitted from a phone to monitor the extent of leaf miner moth infestation in horse chestnut trees
• UK Snow Map Collects tweets with the #uksnow hashtag to build up a picture of where snow is falling
• RSPB’s Big Garden Birdwatch
  Collects data on birds seen in parks and gardens during an hour in one specific weekend

By their nature, Leaf Watch and the Big Garden Birdwatch take time to build up a picture of the data they record. Leaf Watch periodically publishes a map of aggregate data from its survey. The Big Garden Birdwatch publishes its results a couple of months after its survey, which is then repeated the following year.

Only the UK snow map attempts real-time display of information. Naturally enough you want to know where snow is falling NOW – how near to you is it?

The site also vary in how much they allow users to submit their own content. Leaf Watch doesn’t do this at all. The Big Garden Birdwatch has a ‘Community Group’ forum where people who have signed up to the site can crow (pun intended!) about the birds they’ve seen. Posts appear to be reactively moderated.

The UK Snow Map has a live stream of tweets with the hashtag scrolling beside the map. And this is a problem. I’m not that prudish, but many people seem to be unable to refrain from using obscene language even when tweeting about the weather! Actually I wonder if some people make a point of using it, precisely because they know their tweet will appear on screens across the country. Because of this I can’t recommend the site to my children. (There is a facility for only displaying tweets with a positive rating, but you have set it every time you start up the page and it doesn’t get rid of all the rude ones).

It would be much better if there were some sort of filter which ensured that tweets with potentially offensive words in didn’t get displayed. The ‘Scunthorpe problem’, that of censoring innocuous messages because of a rude string of letters, doesn’t really arise because it doesn’t matter whether any particular tweet is displayed or not. It’s still possible to be obscene without using rude words, of course, but I suspect that the Twitter stream would be cleaned up a lot.