[OSM-talk] People's Map

[Keith Ng]

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 at tucny.com> wrote:

> 2009/4/10 Ed Avis <eda at 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
>
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