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Re: Spec is missing 'declination' - body's current pointing angle above horizon

From: Andrei Popescu <andreip@google.com>
Date: Mon, 13 Oct 2008 15:35:18 +0100
Message-ID: <708552fb0810130735l380a68d1sf5a45ab5adb9e030@mail.gmail.com>
To: "Mathew Tizard" <tizardm@yahoo-inc.com>
Cc: "public-geolocation@w3.org" <public-geolocation@w3.org>

Hi Mathew,

Thanks for the suggestion. I think you are right that we're currently
missing an attribute that would allow a complete description of
velocity. Right now, we just have ground speed and heading (angle wrt
the true north). We could add another attribute that would denote the
vertical speed (i.e. the increase or decrease rate of altitude), which
could be more useful than describing this concept in terms of an
angle. What do you think?

Also, please note that the aim of this API is to provide a
geographical position of a body. We currently do not provide
information about the orientation of the body. As a convenience, we do
provide information about the direction of travel (i.e. velocity) but
that doesn't necessarily describe the orientation of the body. I think
that's a quite different matter and probably out of scope for this
version of the API.


On Mon, Oct 13, 2008 at 5:16 AM, Mathew Tizard <tizardm@yahoo-inc.com> wrote:
> Hello,
> I was reading the draft W3C spec for GeoLocation here
> http://dev.w3.org/geo/api/spec-source.html
> It occurred to me that there seems to be a missing attribute in the Position
> Interface.
> You have the following (inherited from the World Geodetic System [WGS84]
> )....
> latitude
> longitude
> altitude
> accuracy
> altitudeAccuracy
> heading
> velocity
> timestamp
> What is missing from this list is the notion of the current pointing angle
> above the horizontal (or tangent to the earth's surface at the relevant Lat
> and Long). May I suggest that "declination" would be the appropriate
> attribute name.
> http://en.wikipedia.org/wiki/Declination
> This would be extremely useful, and would enable specifying a body's current
> motion in space, as well as its position on (or above or below) Earth's
> surface. The compass heading alone does not allow a proper 3D vector to be
> constructed (rather, only motion along the surface).
> Another example: if a user knows their position in a city and wishes to
> point at something in their environment in order to retrieve information
> about it, knowing the angle above the horizontal as well as the direction is
> extremely important. It would be the difference between pointing at a drain
> at ground-level, or a shop at the horizontal level, a second-storey
> apartment, or the moon.
> I was thinking along the lines of using a service like this one
> http://www.earthmine.com/media/ (I am not affiliated to this company).
> Please excuse me if this aspect has already been considered, but it seemed
> important enough to mention to you. I would be interested to hear your
> thoughts on this.
> Best Regards,
> Mathew Tizard
Received on Monday, 13 October 2008 14:37:06 UTC

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