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

Hi Mathew,

Yes, it could be convenient to have this additional variable that together
with the heading could be used to calculate a 3D vector corresponding with
the device's orientation. It could be easily read from the device's
accelerometers if available. As an example, it could be useful for an
hypotethical sky-map application.

However, I think that in navigation and astronomy the right term for this
value would be *elevation angle* or *altitude*. If you take the Horizontal
Coordinate System that uses the observer's horizon as the reference plane,
the altitude gives you this value. So when altitude is 0 degrees, you are
pointing towards the horizon while with an altitude of 90 degrees you are
pointing the zenith (
http://en.wikipedia.org/wiki/Horizontal_coordinate_system)

The declination is used in the equatorial coordinate system which is 2D, and
uses a projection of the earth as the fundamental plane. So declination in
this system would be equivalent to the latitude.

Regards,

Angel