In part one, I presented a sort of background for geotagging and left off with the argument that using what has become the de facto standard for geotagging individual photos and blog entries, is not only counterintuitive, but actually also breaking the conventions so far established for tags. Using the rel="tag" for geotagging is creating implicit rulesets for what tag has to go with which. A tag and a half really makes no sense to the users.
Given that, I think conventions that are specific to the needs of geotagging should be established. Obviously, I can see that there are practical obstacles to overcome; the biggest of which is probably that todays web apps rely on the rel="tag". Also, geotagging with tags is not bad enough to drive a change on its own.
What I’ve noticed though, is that there’s an underlying demand for functionality and standardisation that the current geotagging mechanism can not provide. For tags, the rel attribute provides a means to link to ones prefered tagging service while still enabling other services to aggregate the tag. In essence, it defines a standard for the format of the href. The following all define the same tag:
<a rel="tag" href= "http://technorati.com/tag/geotag"> geotag</a><a rel="tag" href= "http://lemonad.org/geotag"> geotag</a>
<a rel="tag" href= "http://lemonad.org/a/b/c/geotag"> geotag</a>
As one can see, refering the same tags to multiple services is superfluous when it comes to aggregation. For users it’s really also very simple, whether or not you’ve linked the tag to their prefered service, they can easily type it in themselves. The same should be valid for mapping services but the problem is that it’s not immediately obvious that the following url:s are refering to the same latitude and longitude. Different map services also do not share a common mechanism for entering locations:
http://maps.google.com/maps?f=q&hl=en&q=whistler,+bc& ll=50.116726,-122.969799&spn=0.027573,0.077848&t=hhttp://www.mapquest.com/maps/map.adp?searchtype=address& formtype=latlong&latlongtype=decimal&latitude=50.11672& longitude=-122.9697
http://www.terraserver.com/imagery/image_gx.asp?cpx=-122.9697& cpy=50.11672&res=8&provider_id=350&t=pan&OL=Off
Most service providers seem to internally rely on the same datum for coordinates. Yet, one should keep in mind that people are likely to be used to other coordinate representations through their use of gps’.
Now, returning to implementation, it might seem like the obvious way to go is to just combine longitude and latitude into one tag and be done with it.
While this is certainly viable, there are some downsides. Although the tag 50.11672,-122.9697 makes more sense than 50.11672 without its counterpart, it’s still unlikely that you would ever find another blog post with the exact same coordinates. It is also difficult to grasp how that relates to the tag 50.0,-123.0. There’s also upsides though: combining the elements that form geotags makes them behave like proper tags and additionally enables you to use the tag to link to map services.
Still, all in all, I think that using rel="tag" is not the way to go for geotagging. My view is that it’s better to keep it as simple as possible. With rel="tag" the parser should pretty much expect free text after the last forward slash in the url. I’m sure that in some cases it makes sense to create rulesets for parsing the actual tags but that should be less necessary if one would branch off geotagging from tag.
My proposition is that rel="geotag" is used with a clearly defined set of href formats that are suitable for matching with regular expressions. Non geotag-enabled services will simply ignore the tag and those that recognize it know exactly what to do with the information within. Adding the tag geotagged is a workaround for tag services that does not support rel="geotag" based geotags.
What about flickr? Since most people use external services like beeloop.com for assigning geotag information anyway, it should be relatively easy to phase in a new implementation. They could use the geotagged tag for flickr and then rel="geotag"-based links for the description. That way one would not have to rely on flickr to do any upgrades.
What about del.icio.us? There are just 752 entries tagged with geotagged as of today, many of which seems to be about geotagging rather than having location information. As with flickr, one can add the geotagged tag and then use the description field to add rel="geotag" geotags.
Hopefully, I’ve managed to show why a new method for geotagging information should be developed and that it could be done without having to rely on service providers benevolence. There will have to be some iterations before reaching that goal but I think it will be worthwhile in the long run. Note though that I’m just trying to provide one such iteration and in no way am I claiming this to be the goal. Keep that in mind when reading the next part of the series :)
- Part one: geotagging background
- Part three: implementation
- Part four: Future expansions
