I'd suggest using the first three letters, not the airport code. It's a far easier system to remember. Otherwise, if I wanted to find news in Victoria (if I lived in Hamilton, but was going to be travelling there) I'd have to know the Victoria airport code or look it up. Much easier to know it's going to be VIC.

I like using the city name abbreviations, though I edited a couple of them to go with the more commonly used three letter names. Example: HFX instead of HAL and CGY instead of CAL.

I've polled some of the local news outlets and the consensus appears to be to use #LDN for London.

A friend passed this project onto me... I'm a big nerd when it comes to geocoding and standardization and such, so I'm way too keen to be contributing to this for it to be normal. A technical term sometimes used for three-letter alphabetic location codes is a "trigram," for what it's worth.

I don't know if a native Winipegger picked WIN, but I'd recommend against it. WPG is generally used as the short form in sporting context (the Blue Bombers, and I definitely recall it being used for the Jets), and googling "WPG" immediately is interpreted as "Winnipeg." WIN is ambiguous with Windsor, ON. As well, there's probably a fairly substantial battery of hashcodes out there that start with WIN in the sense of referencing MS Windows. Obviously in light of the viral arc these things go through as they catch on, it could be really hard to "change" the dominant hashcode later on down the road, so it might be worth investigate changing it sooner rather than later.

On a related note, MON for Moncton could be problematic if it occasionally got mistaken for Montreal. Are there alternatives, particularly any that seem familiar to Monctonites? MNC? MCT?

I tried to come up with codes for most of the remaining cities in the country that are big enough to get a CMA (Census Metropolitan Area). The most peculiarly Canadian thing about this whole exercise is that the most helpful source for finding preexisting trigrams with some sort of substantial use has been the junior hockey leagues. ;)

#LDN - London
#KWC - Kitchener/Waterloo/Cambridge
#WSR - Windsor
#SHB - Sherbrooke
#BAR - Barrie
#KEL - Kelowna
#ABB - Abbotsford
#SBY - Sudbury
#TRV - Trois-Rivieres
#GUE - Guelph
#BFD - Brantford
#TBY - Thunder Bay
#PBO - Peterborough

My concern about some of these codes is that they require a codebook to remember. Am I going to remember that SHB is Sherbrooke or that TRV is Trois-Rivieres (maybe it was TRI or TRR or something). If you're just tagging your local stuff, having a hard to remember code doesn't matter, because you just have to recall one. But, if you're searching or compiling local content at a provincial or national level you'd start feeling like you're working on cracking the Enigma code. My 2 cents.

I think that straying from the first three letter conventions if ok if warranted and supported by current use. We already changed Calgary to CGY and Montreal to MTL.. And there is still time to kick this around before the official launch of the CanTags on May 1.

I'm ok with changing LON to LDN for London, and Winnipeg to WPG. Using the hockey league conventions might be fine too, just not entirely sure about it at this moment.

Whatever final set of city codes we go with in the end, I think that people will get to know them and use to them over time as messages start to pop up on Twitter and other microblogging services.

Oh yeah, I forgot that we also changed HAL to HFX for Halifax. And thanks for the trigram term tom_A. Can you let us know your first name.

Geo, my first name is, potentially shockingly, Tom. No points for guessing what letter my last name starts with :)

I guess the fundamental question is balancing the need for it to be easy to convert from #FOO to Fooville in one's head versus it being easy to convert from Fooville to #FOO. If I'm scanning some twitter feeds and see a reference to #WINARTS, I wouldn't know if that meant Windsor or Winnipeg. #WPGARTS and #WSRARTS have no such problems.

Also, from a simple rate-of-occurrence perspective, I would imagine it would be more common for someone to read a hashtag referring to an unfamiliar area in someone else's post than for someone to tag a post with a hashtag referring to an unfamiliar area. The latter is going to happen, yes, but so long as we don't have a perfect first-three-letter rule there's always going to be a lingering need for someone to occasionally look things up.

#SHE for Sherbrooke would be quite doable, my only reason for avoiding it was that the pronoun "she" sounds nothing like like the first syllable of Sherbrooke and would potentially lead to an awkward pause while a reader tried to think of city names that did start that way. (Plus, #SHEBIZ sounds like a women entrepreneurs' aggregator ;) ). And I agree Trois-Rivieres is doomed no matter what gets picked.

I guess a question to ask is whether this 'localized' effort is to aid locals in finding tweets about their own city or for people to locate stories in cities other than their own. If this initiative is truly to create a local focus then the local conventions should be adopted. Only when two conventions are identical will someone need to moderate and determine who gets to keep their locally adopted abbreviation.

Great question and suggestions Steve. The aim for CanTags is two-fold.

One, to create a widely shared and understood convention for news on Twitter and other microblogging services, so that whether you are an individual who wants to share news about your neighborhood, city or country, you can do so easily. This goes for news organizations too. There has been a great deal of interest in CanTags from pro journos.

The other goal is to have a convention that makes it easy to retrieve news items from Twitter, Flickr, blogs and other online services via hashtags. So having naming conventions that are as consistent and as widely shared as possible can help faciliate that.

People in Peterborough will go with the PBO if there's a hockey precedent to cite.

I would argue against KWC for Kitchener/Waterloo/Cambridge. As someone who's lived in Kitchener most of my life, we do say K-W, but we almost never include Cambridge in the same breath. And people who live in Cambridge tend to say they live in Galt, Hespeler, or Preston, having been victim to an enforced city many years ago. I posted something this morning and used #WAT for Waterloo. Sometimes lumping them together makes sense, sometimes not.

I agree that KWC is lame. I support WAT, KIT and I don't know for Cambridge, CMB?

Also, if St. John's, NL is STJ, what is St. John, NB . . . SJB?

Thank you Clare and Ryan for helping us fine-tune the city codes. Wel'll adjust according to your suggestions. We by no means have a complete and final list of city codes so every bit of advice helps us get closer to that goal.