Most of the mobile devices today support GPS geo tagging. In fact most of them come bundled with navigation software that uses GPS and therefore all the pictures and (maybe) videos can be geo tagged. But as expected different vendors come with different support and formats.

iPhone OS comes with geotagging both on video and image files, while the latest Android and Symbian (the Nokia main OS for smartphones) can geo tag only images.

Even more – until recently Symbian didn’t support any geotagging before the installation of an additional software – such as Location Tagger . So generally the things are quite simple:

1. iPhone OS geotags both video and image files;
2. Android geotags only images;
3. Symbian geotags only images – and on some devices this is possible only after installing a software;

This is in breve the state of mobile device geotagging!

Why Use GPS Data?

Perhaps one of the main reasons why not support geotagging especially on video files can be the usage of those geo tags. First of all what a geotag means?





You may know that even Android doesn’t “geotag” videos this is not quite true. Because after using you gallery you can see where those videos are shot. This is fantastic, but actually the real information about where the video has been taken is not into the video file, but it’s in an additional log file that keeps it. Thus actually the video files doesn’t know the geo coordinates.

Here comes the problem with video format, because you cannot be sure that every format supports tags that can keep geo coordinates. Actually quicktime’s MOV can store them, while Symbian’s 3GP cannot. In fact Symbian cannot store any geo information about video files!

So now we’ve at least three different formats for each of those three vendors.

1. quicktime for iPhone
2. mpeg-4 with Android
3. 3gp with Symbian

For now I can only say that iPhone can keep the geotag into his video files.





But let me return to the question – why we need this geo tags? Until the video file is on the mobile device – there’s no problem. But once you try to download it – whether on Flickr, YouTube, Picasa, etc. you’ll lose any geo information if it’s not into the file tags. And of course if the above sites can’t read it!

The general reason to store this data into the file is to move it along with the file. Once you move this file from your mobile device to a web platform you’ll see where the file has been created.

EXIF, Exiftool and PHP’s exif_read_data

There are several tools to read geotags. For images, and here we talk only for JPEGs, this is the EXIF information. You can download the exif command line program and try to reed data with it:

exif filename.jpg

Which can result in something like that:

Manufacturer        |Nokia                                                     
Model               |E71                                                       
Orientation         |top - left                                                
x-Resolution        |300.00                                                    
y-Resolution        |300.00                                                    
Resolution Unit     |Inch                                                      
YCbCr Positioning   |centered                                                  
Compression         |JPEG compression                                          
x-Resolution        |72.00                                                     
y-Resolution        |72.00                                                     
Resolution Unit     |Inch                                                      
FNumber             |f/3.2                                                     
Exif Version        |Exif Version 2.2                                          
Date and Time (origi|2011:01:24 12:15:01                                       
Date and Time (digit|2011:01:24 12:15:01                                       
ComponentsConfigurat|Y Cb Cr -                                                 
Aperture            |3.20 EV (f/3.0)                                           
Light Source        |0                                                         
Flash               |Flash did not fire, auto mode.                            
Focal Length        |4.9 mm                                                    
FlashPixVersion     |FlashPix Version 1.0                                      
Color Space         |sRGB                                                      
PixelXDimension     |2048                                                      
PixelYDimension     |1536                                                      
Custom Rendered     |Normal process                                            
Exposure Mode       |Auto exposure                                             
White Balance       |Auto white balance                                        
Digital Zoom Ratio  |1.00                                                      
Scene Capture Type  |Standard                                                  
GPS tag version     |0x02, 0x02, 0x00, 0x00                                    
North or South Latit|N                                                         
Latitude            |42.00, 39.00, 24.67                                       
East or West Longitu|E                                                         
Longitude           |23.00, 21.00, 28.45                                       
Altitude reference  |0x00                                                      
Altitude            |625.50 

While for video files (iPhone) exif cannot help you, this is possible through Exiftool. With it you can read even iPhone video geotags:

./exiftool filname.mov

In addition this information can be read with PHP via exif_read_data:

$info = exif_read_data('filename.jpg');
var_dump($info);

And this will give you not only standard tags, but geo tags too.

Do as Twitter did … or you’d be looking at http://m.digg.com/ – that’s the right way.

Have you ever noticed that once you start designing a site for mobile, as iPhone and Nexus One from Google are, the site is looking really ugly! These two devices in particular, as may other using Opera Mini for instance, scale the site, because only than you can view the entire layout and than zoom to a particular part of the page.

This is nice because news sites as cnn.com or lemonde.fr are full of text & image information and once zoomed in they fit the screen – very nice feature of the browsers. However if you’d like to design a site for mobile the bad part comes here. Yeah you know how to detect the browser, that was a topic of one of my previous posts, but even than you fully functional, but less decorated site is scaled again and looks more ugly than the full version of the site.

How to make a site visible in mobile …

Look at the http://mobile.twitter.com/ – the problem is that if you open this link with a normal browser, not from mobile, you’ll get redirected to the twitter.com and you cannot see the difference.

You can see how it’s made on …

The digg’s mobile version. Look at http://m.digg.com/. This time you can see the different approach just by looking at the source code. Pay attention to meta tag in the head – it simply says – “don’t scale”. Nice thing to notice!

Don’t scale my site anymore:

<html>
 <head>
  <meta name="viewport" content="width=320; initial-scale=1.0; maximum-scale=1.0; user-scalable=0;"/>
 </head>
...
</html>

Beside that most of the responses of $_SERVER[‘HTTP_USER_AGENT’] may return, it appears that this is the most reliable way to track down a user agent with PHP. It is weird that most of the clients, i.e. Safari and Chrome will return something with Mozilla in it’s strings, but however it’s enough to track the “chrome” or “safari” sub strings.

All the examples bellow are from Mac OS X:

Firefox 3.6:

Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.2) Gecko/20100115 Firefox/3.6

Note: there are both Mozilla and Firefox sub strings!

Safari 4:

Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_5_8; bg-bg) AppleWebKit/531.21.8 (KHTML, like Gecko) Version/4.0.4 Safari/531.21.10

Chrome:

Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_5_8; en-US) AppleWebKit/532.9 (KHTML, like Gecko) Chrome/5.0.307.11 Safari/532.9

Note: Here they are Mozilla, Chorme and Safari!!!

Opera:

Opera/9.80 (Macintosh; Intel Mac OS X; U; en) Presto/2.2.15 Version/10.10

The day of mobile

Nowadays it’s normal to make a site with the presumption it will be visible from mobile. The war between Nexus One from Google and iPhone from Apple is just beginning and with all those devices with wide screens everything’s becoming more complicated.

User agent strings from Nexus One and iPhone

Both are weird, but both contain the keyword – “mobile” and that may help you make a check with something like this PHP snippet: