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RE: Question on gps info in cellphone-snapped pictures -- for short article on mobile web

From: CE Whitehead <cewcathar@hotmail.com>
Date: Wed, 9 Feb 2011 14:18:59 -0500
Message-ID: <SNT142-w404E4625898DFF06FF1236B3ED0@phx.gbl>
To: <boyera@w3.org>
CC: <public-mw4d@w3.org>

Hi Dr. Boyera:
 

> Date: Wed, 9 Feb 2011 08:57:47 +0100
> From: boyera@w3.org
> To: cewcathar@hotmail.com
> CC: public-mw4d@w3.org
> Subject: Re: Question on gps info in cellphone-snapped pictures -- for short article on mobile web
> 
> Hi CE,
> 
> Thanks for your questions. I'm happy to give it a first shot.
> 
> > 1. I am interested in mobiles' picture-snapping capability. Is the .gps
> > ever automatically included in the .exif file in the picture? Or does
> > the .exif normally include just the time unless you first generate a
> > .gps location track and then matched with the time data in the .exif files?
> 
> First of all the availability of GPS on phone is very very rare in most 
> developing countries, and only in the high-end part of the market.
> Then in the smartphone world, i believe that most gps-enabled handset 
> are able to geotag photo in exif see for instance: 
> http://en.wikipedia.org/wiki/Exchangeable_image_file_format#Geolocation
> Even some non-gps enabled phone are sometimes able to geotag 
> approximately the images.
I see; so providing that the right phone was used, someone could in theory photograph water supplies and runoff (and collect data as well though that's irrelevant here), and those photos could  be tagged with the geolocation, even in Africa? (Correct me if I'm wrong . . . otherwise thanks for this info.)
> 
> > 2. Is having a mobile-ready web page normally include the idea of
> > having a page that does not take much bandwidth to download? And is the
> > likelihood of getting a 404 not found message in the third world
> > increased because of bandwidth issues?
> 
> there are two parts in your questions.
> i start with the latest one: you would never get a 404 due to bandwidth 
> issue. a 404 is generated and send by a web server, so that that means 
> that your request has reach the targeted web server which in does not 
> have the right page and tell you so. The lack of bandwidth would give 
> you a 'connection timeout' but not a http error code.
> The bandwidth issue is at different level too:
> - between the user and the internet: ie the pipe of the operator, the 
> signal and the handset. the bottleneck can be between the user and the 
> data service provider (ie the operator). there are at least three major 
> reasons for such a bottleneck: the type of data service (GPRS vs 3G 
> etc): in most countries today in e.g. Africa only GPRS is available 
> outside urban area, which means a couple of KB of bandwidth only.
> Then you might have a great 3G signal, but if your phone is only a 
> GPRS-enabled one you wouldn't see any difference.
> Finally, even gprs itself has a theoretical bandwidth and an effective 
> one, which highly depends on the position of the user vis-a-vis the 
> tower. the weaker the signal, the lower the bandwidth.
> - between the operator and the requested web site: even if the user has 
> a great connection to his provider, then the bottleneck could also be on 
> the international bandwidth between the operator and the targeted site.
 
Thanks very much for this detailed reply; I will quote you.  Best wishes.
 
Sincerely,
 
--C. E. Whitehead
cewcathar@hotmail.com 
> 
> All in one, it is clear that the bandwidth available to user in 
> developing countries is almost always low. It is therefore critical to 
> ensure that coding techniques and content development techniques takes 
> that constraints into account.
> It is also important to note that the bandwidth is not the only reason 
> for making the page small. As most data service plan (pre or post paid) 
> are based on time or size of content, making small content means a 
> cheaper one for the user. There are also device limitation, particularly 
> memory limitation that would make some bigger content not 
> usable/accessible/displayable on some devices.
> 
> The Mobile Web best practices (MWBP http://www.w3.org/TR/mobile-bp/ ) 
> has a lot of recommendations concerning small content.
> However, most of the MWBP are about why to make small content, and 
> where, but not really how. This is more hands-on expertise. For instance 
> W3C has online training courses with specific modules on this topic 
> (http://www.w3.org/2009/03/mobitrain_course_description.html )
> The Web Foundation is running face-to-face training in Africa with also 
> modules on this topic (see http://www.mobilewebghana.org/training.html )
> 
> Let me know if you have other questions
> Stephane
> 
> -- 
> Stephane Boyera stephane@w3.org
> W3C +33 (0) 5 61 86 13 08
> BP 93 fax: +33 (0) 4 92 38 78 22
> F-06902 Sophia Antipolis Cedex, 
> France
 		 	   		  
Received on Wednesday, 9 February 2011 19:19:33 GMT

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