I didn't actually calculate the field of view in degrees, because that would be harder at this time in the morning ;) working out how much area they would cover is pretty simple though if you are happy to guess what resolution camera they used... I went with a 10MP camera, such as a Canon EOS 1000D, which has an output resolution of 3888 x 2592px... If the resolution is quoted as 12.5cm per pixel, 3888 of them would be 486m :) Then, knowing that the picture has been taken from 1676.4m up, making some more assumptions about the camera being aimed directly at the ground you can work out all the angles involved as you are dealing with a right-angled triange with a height of 1676.4m and a base of 243m (half of the 486m worked out previously), all the information you need :)
d 2009/4/10 Keith Ng <khensth...@gmail.com> > How does one go about calculating the field of view from the elevation and > resolution? Would you mind explaining that? Thank you very much. > > On Fri, Apr 10, 2009 at 11:30 AM, D Tucny <d...@tucny.com> wrote: > >> 2009/4/10 Ed Avis <e...@waniasset.com> >> >>> Pieren <pieren3 <at> gmail.com> writes: >>> >>> >>http://wiki.openstreetmap.org/wiki/Aerial_photography_funding_appeals >>> > >>> >The wiki says about this supplier: >>> >About $17 per sq km for basic 2 meter resolution photography. >>> >>> Does that mean that each pixel covers an area roughly 2m by 2m? If so >>> this is >>> not any better than the Yahoo aerial imagery that OSM can already use for >>> many >>> countries. (It could still be worth buying for places not covered by >>> Yahoo.) >>> >>> The aerial photographs used by People's Map are from getmapping.com (in >>> fact, it >>> seems to be run by the same people somehow) and those have a resolution >>> of >>> either 25cm or 12.5cm. That's the kind of detail that would really help >>> with >>> mapping those council estates and car parks. >>> >>> < >>> http://www2.getmapping.com/Support/Aerial-Photography-Coverage-%281999-to-2003%29 >>> > >>> >>> At this detail level they will sell a 10km * 10km area for 1850 GBP. At >>> least >>> nine such areas would be required to cover inner London (the area of a >>> 'Mini >>> A-Z'). However, this price is for '1 to 10 hard copies' - I don't know >>> how much >>> they would want in exchange for providing photos that can be used in OSM. >>> Since >>> OSM is a competitor to People's Map, they might ask a lot. >>> >>> >> The reason getmapping has such a high resolution is that they are not >> using satellites... they capture images from 5500 feet (1676m) according to >> their site... If they were using a 10 mega-pixel camera, getting a 12.5cm >> resolution would give them a field of view covering 486m x 324m, or double >> that for 25cm resolution, they'd have to do a lot of flying just to cover >> the UK, let alone the rest of the world... In comparison, satellite imagery, >> which for commercial use currently has a best resolution of 41cm (apparently >> downgraded to 50cm due to US Government controls) in monochrome, 2.4m in >> full colour, takes shots that can be 15km wide and hundreds of km long... >> They do cost a bit to build, launch and manage though... >> >> How much does a small plane with camera mount cost to hire for a day? :) >> >> d >> >> _______________________________________________ >> talk mailing list >> talk@openstreetmap.org >> http://lists.openstreetmap.org/listinfo/talk >> >> > > _______________________________________________ > talk mailing list > talk@openstreetmap.org > http://lists.openstreetmap.org/listinfo/talk > >
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