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01 September 2008

Locatable roadmap and feature planning

I thought I'd give an update on where I'm going with Locatable and I'd love to hear feedback or suggestions for new functionality. I've just tested a better technique for saving data to the client-side database from the Locatable application which means that the app itself should not need any network connectivity. This is good news as there's a risk of settings becoming unsynchronized between the app and the database the way it's working right now (e.g. if the connection fails). This means rewriting all the preferences-saving and preferences-loading code and won't have any visible effect on the UI. Preferences anyway are about to get more complex. Now that Locatable is tracking per-site preferences (so you can choose to only be prompted once or twice per site to share location), there needs to be a UI to see what sites are currently in the list and manage their individual settings. I'm thinking of it a lot like the cookie manager in Firefox — you should be able to blacklist and whitelist individual sites that you visit, as well as alter their settings individually. So that's the task for Locatable 0.4. The other item on the TODO list requires a schema upgrade, which is why I've been procrastinating on it. It would be good to store the horizontal accuracy of the reading so this can be shared (via the W3C API and redirector). It would be nice to have altitude and vertical accuracy as well, though I'm not sure if these even work (certainly not on an iPod Touch!). Once those are in there, the plan is to submit to the AppStore. If accepted, the only difference between the jailbroken version and the AppStore one will be the inclusion of Relocatable, which of course won't work. (I won't be discontinuing development on it, but it may become its own package in Cydia.) In the meantime I'm open to suggestions on other functionality that should be included. Primarily what I've been hearing about is people using Relocatable to do their own lojack-type apps. I'd really like to get some feedback on using Locatable on your web sites to integrate positioning data, do maps mash-ups, and so on. Private feedback is fine, public is even better (and I'll be happy to put links on the Featured Sites page).

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28 August 2008

The W3C Geolocation API on iPhone with Locatable

I've ported the W3C's draft Geolocation API so it can be used from an iPhone with Locatable installed (my Javascript skills are far from elite, but with enough prodding and old-school alert() debugging, I got there). This means that in addition to the redirect API (which is nice for embedding static links to pages that can take lat/long coordinates), you can now get at location information on demand via Javascript, through what is likely to become the standard API in future browsers. To use it, just include this in your HEAD:
<script type="text/javascript"
src="http://lbs.tralfamadore.com/w3c-api.js">
</script>
You can download and install the script locally if you like (but please check back for new versions from time to time). Then, to use it, just use the standard W3C-prescribed approach via a global object called Locatable, e.g.
// Callback handler
function gotLocation(position) {
alert('You are at (' + position.latitude + ','
 + position.longitude + ').');
}

// Use this anywhere you like
Locatable.getCurrentPosition(gotLocation);
The only addition to the W3C API is an isEnabled() method. This will attempt to figure out if the API will work on the current browser. Right now this merely checks if someone is on an iPhoneOS device, but might be more sophisticated in the future. There's a test page up at http://www.tralfamadore.com/test-w3c.html that demonstrates this functionality. Some implementation notes:
  • The same logic applies when sharing location as with the redirector. Depending on user preferences, an alert will ask them to confirm if they want to share their location. If they decline, you'll get an error callback if you provide the second argument to getCurrentPosition.
  • If the location needs to be refreshed, the app will launch, update the reading, and then return to Safari. This can take some time (in Locatable 0.3, up to 20 seconds, depending on the user accuracy setting). On jailbroken phones with default Locatable settings this is unlikely to occur as the daemon will be updating location in the background, but an AppStore version will not have this advantage, so be mindful of this.
  • W3C PositionOptions (the accuracy hint) does nothing at the moment.
  • watchPosition() is "implemented" (that is, the function exists), but you'll only ever get one reading, so it's not entirely useful.
  • The accuracy reading in the position object is currently the user-set minimum accuracy level (a round number like 10, 100, or 1000 meters), not the device-reported accuracy of the reading itself. This is likely to change in future versions.
  • Altitude and velocity are not implemented yet and yield null values.
  • w3c-api.js will attempt to detect if you're running an iPhone or iPod Touch and not install itself otherwise. It also won't overwrite navigator.geolocation if it's already implemented (non-null).
  • It probably goes without saying, but you should include the w3c-api.js script on every page you want to use it in.
I'd consider this a beta version — I've done some basic testing but haven't tried too many use cases. Let me know how it works for you in the comments. Update (31 Aug 08): Upon some reflection, I decided it's best not to try to automatically install as the navigator.geolocation global, so the script has been updated to use a global called Locatable (capital L) instead. You're free to assign it to navigator yourself (i.e. navigator.geolocation = Locatable). Also added the isEnabled() method.

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27 August 2008

Changelog for Locatable 0.3

I'm just about to submit the new version of Locatable. Here are the changes: Locatable
  • More accurate GPS readings. When retrieving a location, wait until the accuracy is within the specified range, or 20 seconds, whichever comes first (i.e. if you set it to "Best", it'll spend the full 20 seconds).
  • New option "Expire after" specifies how stale of a location is allowed to be sent to web sites. Default is 10 minutes. If you set this to "each request", Locatable will pop up every time a web site wants to read your location.
  • New option "Ask permission" defines if and how many times you'll be prompted to allow a site to see your location. Default is to always ask. Set this to "Twice per site" to mimic the behaviour of iPhone native apps.
Relocatable
  • Relocatable is now a daemon process. You can control how often and how fast it runs by editing /System/Library/LaunchDaemons/com.tralfamadore.locatable.plist.
  • You can also run it from the command line (it now lives in /usr/libexec/relocatable), which gives you the following options:
~ root# /usr/libexec/relocatable/Relocatable -h
Usage: Relocatable [-v] [-t SECONDS] [-d SECONDS] [-e CMD]
-d SECONDS      run as a daemon, delay specified seconds between fixes
-e CMD          execute given program (with args) after each location fix,
                 can include @lat@, @long@, and @hacc@ tokens
-t SECONDS      spend specified seconds waiting for a fix, default 30
-v              turn on verbose logging
Let me know if you encounter any issues. Update (30 Aug 08): A few people had questions about getting the command execution piece to work. Here's an example — the important bit is to wrap the whole command in single quotes, otherwise the shell gets confused. First, if Relocatable is already running as a daemon (it will be by default), you need to stop it:
~ root# launchctl unload /System/Library/LaunchDaemons/com.tralfamadore.locatable.plist
Once that's done, you can run Relocatable as a one-off from the command line:
~ root# /usr/libexec/relocatable/Relocatable -v \
> -e 'curl "http://my.site.com/savepos.pl?lat=@lat@&long=@long@&acc=@hacc@"'
Opened LBS database for read...
Started updates...
newLocation: <+51.xxxxxxxxx, -0.xxxxxxxx> +/- 93.21m @ 2008-08-30 13:17:44 +0100
newLocation: <+51.xxxxxxxxx, -0.xxxxxxxx> +/- 93.21m @ 2008-08-30 13:18:29 +0100
Stopped updates
Opened LBS database for write...
* About to connect() to my.site.com port 80 (#0)
*   Trying xxx.xxx.xxx.xxx... connected
* Connected to my.site.com (xxx.xxx.xxx.xxx) port 80 (#0)
> GET /savepos.pl?lat=51.xxxxxxxxxx&lng=-0.xxxxxxxxxxxx&acc=93.21 HTTP/1.1
> User-Agent: curl/7.17.1 (arm-apple-darwin9) libcurl/7.17.1 OpenSSL/0.9.8g zlib/1.2.3
Note the use of the single quotes (to bracket the command passed to Relocatable) and double quotes (to bracket the URL, so it can contain characters that would otherwise confuse the shell, like the ampersand). The same rules regarding quoting apply to editing the daemon plist. Once you're happy with your settings and have edited the plist to your satisfaction, remember to start it back up:
~ root# launchctl load /System/Library/LaunchDaemons/com.tralfamadore.locatable.plist

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18 August 2008

Geohacking with Locatable

Locatable has had well over a thousand downloads in the first 12 hours, so I've just been updating the featured sites to give everyone something to play with. I haven't yet heard of any "made for iPhone" sites that can take advantage of the latitude/longitude sharing feature of lbs.tralfamadore.com, so for now the links you'll find there are publicly available web sites and services that take lat/long coordinates. I used some of the more common online mapping services to test during development, but now that I have a little more time to browse around, I'm finding a lot of interesting things that can be done already:
  • Geocaching. Use your iPhone to participate in local treasure hunts.
  • GeoNames. Find and identify nearby landmarks.
  • Panoramio. Look at photos that have been taken near your location.
Here are some things I'd love to see but haven't tracked down yet (even if they don't yet exist as lat/long-enabled URLs, the mashup would be easy to do): movie listings, traffic reports, friend finder, turn-by-turn spoken driving directions, emergency services finder, shop finder (Apple store, anyone?), and so on. Maybe I'll hunt around a little later. In the meantime, let me know if you have any links to post.

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15 August 2008

Sneak peek

I'm close to a beta release for Locatable, and I'm excited enough about it that I wanted to give a quick preview, from a tech-centric point of view. Locatable is an application and geolocation federation service that let you share your location (GPS coordinates, or any decent facsimile thereof) from your iPhone or iPod Touch to any web site, via the built-in Safari browser. It takes advantage of the new client-side storage capabilities of Safari to allow some very nice anonymity and privacy features -- notably, the user's location is never stored on the server side, with the service at lbs.tralfamadore.com acting as a gateway to storage on the device. There's a lot to say about this and its relationship to similar services such as MyLoki (Skyhook) and FireEagle (Yahoo!). Both of those could be integrated, as can just about any existing location-based service. Anyway, check out the concept and check back for more updates soon.

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