Even if you're not a cartographer, when you first see a map there's almost always a gut feel for whether you like a map or whether you don't. Critiquing a map is a deeply subjective thing. You may not know why you like a map but you can tell whether the map's cartography works or it doesn't work, for you at least.

The image at the top of this post is a great example of what I mean by this. It's a map of Berlin on the inside of an umbrella. Which is a great idea and this map is one I'm very fond of, both because of the time I spent in Berlin and because it was a present from one of my old HERE Maps team. But as a map, it's far from pleasing to me; I love what's being mapped, I just think it needs a better cartographer.

So much of what appears on today's digital maps is crowdsourced. Whether it's a totally crowdsourced map such as OpenStreetMaps' or a more focused effort such as HERE's Map Creator or Google's Map Maker, the so called wisdom of the crowd is an integral part of so many maps. But what would happen if you tried to crowdsource the critiquing of maps rather than the map itself?

Imagine for a moment you're in the city you live in; you know it like the back of your hand and yet you know there's shops, businesses or services nearby that you haven't yet come across. Or maybe you're in an unfamiliar city and you want to explore and stay away from the same old global brands that you see everywhere, in every city and on every street.

Now imagine putting this on a map.

"Ah hah!" you might say, reaching into your pocket and brandishing your smartphone. "I can do that easily" you say triumphantly as you fire up Google's or Apple's or HERE's mapping app.

But no, I'm talking about something a little more focused, a little less broad. "No worry" you say, firing up Foursquare, or Yelp or Facebook or TripAdvisor.

CartoBot is a small robot who lives in the office in my loft. He accidentally achieved consciousness when his charging cable was accidentally plugged into a Raspberry PI and he started to look for information. His only source was my library of books on maps and so CartoBot became obsessed with them. He now spends his days sitting on my home wifi connection and scouring the web for maps and mapping related stuff, which he Tweets about through his very own Twitter account.

None is this is true. Sorry CartoBot, it's just not. Cartobot is a Twitterbot, written in Node.js, that searches for Tweets about maps and cartography and also scans my GetPocket queue for bookmarks tagged with maps and Tweets about these as well.

In English, null means nothing, nil, empty or void. In computing, null is a special value for nothing, an empty value. In geography, null tends to be what you get when you've been unable to geocode a place or an address and haven't checked the geocoder's response. What you end up with is a pair of coordinates of 0 degrees longitude and 0 degrees latitude, a point somewhere in the middle of the Atlantic Ocean, south of Ghana and west of Gabon. It's here that you'll also find Null Island, if you look hard enough.

The website for the Republic of Null Island (like no place on earth) says this about the island's location ...

The Republic of Null Island is one of the smallest and least-visited nations on Earth. Situated where the Prime Meridian crosses the Equator, Null Island sits 1600 kilometres off the western coast of Africa.

... but Null Island is an in joke created by Nate Kelso and Tom Patterson as part of the Natural Earth data set in January 2011.

Running between Edgware, Mill Hill East and High Barnet to the North of London to Morden to the South, the London Underground's Northern Line stretches for 36 miles and takes in 50 stations. The line, marked in black on the Tube map, is a familiar sight to London commuters. But is the map of the line accurate? Does it reflect reality?

A geographic map of the line looks something like this. The Northern spurs of the line merge at Camden Town and then split into two branches, one via Charing Cross and the other via Bank, before merging again at Kennington and heading towards the Southern terminus at Morden.

My morning's reading today has been dominated by a map image that the UK's Environment Agency released on December 6th that, to quote the Tweet, shows "the extent of potential flooding of London if the Thames Barrier wasn't in place". If you know London at all, it's certainly an arresting image but like so many times when I encounter a map, I want to interact with it, move it, see whether where I live in London would have been impacted. So I started investigating.

Some background context is probably in order. On December 5th. the UK's Met Office issued severe weather warnings for the East Coast of England. A combination of a storm in the Atlantic to the north of Scotland, low atmospheric pressure and high tides were all combining to push a massive swell of water through the narrows of English Channel, in effect squeezing the water through the Dover Strait. As the North Sea and English Channel are relatively shallow, the sea would back up and had the potential to flood large areas of the East Coast of England as well as the areas surrounding the tidal stretch of the River Thames and that means London and possibly even where I live in Teddington, which marks the upper limit of the tidal Thames. Thankfully for those of us who live West of Woolwich, the Thames Barrier exists to protect London from such flooding, though I'm sure this is less of a comfort to those people who live to the East of the barrier.

Oh look. It's another reworking of Harry Beck's London Underground map. Ken Field probably won't like it. This one is Doctor Who related. All the usual suspects are present. Each line representing one of the Doctors? Yes. Stations representing monsters and adversaries? Yes. Vague notions of interchanges between the lines? Oh yes.

Now I'll freely admit I've been more than guilty of writing about re-workings of this particular map, at least 12 times. Doctor Who has been on, then off, then back on our TV screens for 50 years; longer than I've been around, but only by 2 years.