Vincent MEURISSE <[email protected]> Sent by: [email protected] 16/08/2009 14:47 Please respond to [email protected]
To [email protected] cc Subject Re: [OSM-dev] OpenStreetView: Digital Photos: Getting the field of view angle On Sunday 16 August 2009 14:42:26 Nick Whitelegg wrote: >> 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)? >The formula is : >Tan(angle/2)=size of film/(2*focal) >for a standard film you get and a 50mm objective: >size of film = 24x36 (diagonal=43.3) >so angles are: >vertical 27° >horizontal 39.6° >diagonal 46.8° Thanks for the replies on this. What I'll probably do is put up my thoughts for how this app should work on the blog http://www.openstreetview.org.uk/wordpress/. One question about something which I *think* should be possible: is it possible to overlay a ground (not aerial) photo on a DEM? In, say, OpenGL, if you set the field of view and aspect ratio to the same as the photo, I'd imagine you could overlay a ground photo on a DEM generated from, say, SRTM. There would be a number of issues, principally the inaccuracy of the SRTM data, plus the presence of trees, etc, but I'd imagine it would be theoretically possible. Nick > 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? In fact you don't really need the size of film (captor size). Most of the camera store the focal in both real and equivalent distance. If I take a random picture from a nikon D300 the exif information contain this: Focal Length: 70mm Focal Length In 35mm Film: 105mm Digital zoom ratio: 1.0 So with the equivalent focal and the digital zoom, you can get your angle. -- Vincent MEURISSE _______________________________________________ dev mailing list [email protected] http://lists.openstreetmap.org/listinfo/dev _______________________________________________ dev mailing list [email protected] http://lists.openstreetmap.org/listinfo/dev
