[OSM-dev] OpenStreetView: Digital Photos: Getting the field of view angle

[Thomas Wood]

I've seen some quite awesome apps on the iphone that allow for
augmented reality. http://layar.eu/ is one such example from a quick
google. And another - http://www.youtube.com/watch?v=5fZk0HaIs4s

2009/8/16 Nick Whitelegg <Nick.Whitelegg at solent.ac.uk>:
> Hello everyone,
>
> Have been thinking a bit more about my own interests within the
> "OpenStreetView" project introduced by John McKerrell at SOTM. My
> particular interest is an in the field navigation tools for countryside
> users, particularly walkers/hikers/mountaineers etc, which I'm giving the
> codename "footnav" for the moment (seeing as John already has
> openstreetview and I'm more focusing on the countryside!)
>
> One option is simply to have a computer generated 3D view from SRTM, OSM
> and 3D models of stiles, gates and so on. However I'm quite interested in
> using actual photos: the advent of "compass phones" such as the N97 and
> latest iPhone makes this a realistic possibility.
>
> What I'd like to do is build up a database of photos taken along a path or
> footway, say every 10 metres or so. If a user wanted to navigate, the app
> could locate the nearest photo to them, based on location and direction of
> travel, and display it, with their position and OSM data overlaid on the
> photo. I was on top of a hill looking down at a valley the other day and
> was thinking "how cool would it be if I could see a photo of that valley
> and have all the footpaths overlaid on it"!
>
> I've done a bit of OpenGL and believe something like this could be done if
> the position, direction, slope, aspect ratio and field-of-view angle of
> each photo were known. Most of these I have ideas on how to obtain, or at
> least where to go to look it up, *except* the field of view angle.
>
> The thing I don't really know much about is: how can you get the
> field-of-view angle of a photo taken from a digital camera (either a
> standalone camera or within a phone)? I've seen a few explanations on the
> web on how you get it from the focal length (which appears to be quoted in
> e.g. the N95 specs) but they also require another parameter (the "size of
> the film"). Where might I get this from?
>
> If anyone's an expert on photography theory I'd welcome any explanations
> on how to obtain the field-of-view angle of digital photos.
>
> Thanks,
> Nick
>
>
>
>
>
>
>
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-- 
Regards,
Thomas Wood
(Edgemaster)