[OSM-newbies] Trust Yahoo or OSM?

[Kevin Samples]

Be aware that buildings may appear to be shifted in comparison to the 
Yahoo aerial images or any aerial imagery, but actually are not.  In 
aerial photography any structure that has hight will exhibit parallax 
(sometime drastically) and will appear to be tilted away from the center 
of the image (central perspective).  If buildings are drawn from any 
aerial photograph, the building should be traced from it's base where it 
has contact with the earth in order for it to be properly aligned on the 
map.

Kevin

Habib Habib wrote:
> Thank you guys for your answers.
>
> As for my original problem, I noticed that streets were aligned with 
> Yahoo images while buildings are not, therefore I assumed that 
> buildings are wrongly placed.
>
> On Mon, Sep 14, 2009 at 8:06 AM, Aspen Swartz <aspendel at gmail.com 
> <mailto:aspendel at gmail.com>> wrote:
>
>     > ------------------------------
>     >
>     > Message: 10
>     > Date: Sun, 13 Sep 2009 21:18:11 -0600
>     > From: James Ewen <ve6srv at gmail.com <mailto:ve6srv at gmail.com>>
>     > Subject: Re: [OSM-newbies] Trust Yahoo or OSM?
>     > To: newbies at openstreetmap.org <mailto:newbies at openstreetmap.org>
>     > Message-ID:
>     >      
>      <fe2e5b210909132018k625a8810s9ad6eac332ff6704 at mail.gmail.com
>     <mailto:fe2e5b210909132018k625a8810s9ad6eac332ff6704 at mail.gmail.com>>
>     > Content-Type: text/plain; charset=ISO-8859-1
>     >
>     > On Sun, Sep 13, 2009 at 4:54 PM, David Ellams
>     > <osmlists at dellams.fastmail.fm
>     <mailto:osmlists at dellams.fastmail.fm>> wrote:
>     >
>     >>> The aerial photos can be displaced slightly. Potlatch has a
>     built in
>     >>> facility for moving the background photo to align it to the real
>     >>> world.
>     >>
>     >> Sorry, I am not clear - are you saying Potlatch will allow you
>     to move
>     >> the Yahoo photography from its default position? If so, please
>     could you
>     >> let me know how, as I cannot see an option.
>     >
>     > Go to http://www.openstreetmap.org in your browser. Zoom in to level
>     > 13 or better so that the edit button becomes available. Click on
>     edit,
>     > and then select either "Edit Live", or "Edit with Save". Once
>     you have
>     > Potlatch running, on the bottom of the screen is a button that
>     has the
>     > word "Help" on it. Click that button, and a help screen opens up. On
>     > the top of the help screen, click on the word "Surveying". The last
>     > paragraph under "Using Satellite Photos" describes the process for
>     > shifting the photos against the map.
>     >
>     > While you have the help screen open, take a bit of time to read the
>     > information provided. Potlatch is actually a collection of fairly
>     > powerful tools, and information on how to access those tools is
>     > available in the help file.
>     >
>     > Now, you are probably thinking that it would have been much
>     easier to
>     > simply say "Hold down "Space", and drag the background", but I'm
>     > hoping you and others will actually take the time to read the help
>     > file rather than keep asking those who have read the help file to
>     > regurgitate it for you. Richard went to the trouble to create
>     the help
>     > file, the least we can do is read it.
>     >
>     > It's the old "Teach a man to fish" adage...
>     >
>     > The real short answer would have been RTFHP. 8)
>     >
>     > James
>     > VE6SRV
>     >
>
>     Thank you, that was very clear and just the sort of learning I signed
>     up to the newbies list for.
>
>     Aspen (eulochon)
>
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