- From: Steve Block <steveblock@google.com>
- Date: Tue, 5 Jul 2011 13:39:44 +0100
- To: George Percivall <gpercivall@opengeospatial.org>
- Cc: public-geolocation@w3.org
> With rotation, acceleration will be different at different points in the > device. True, but I still don't see the need to specify the origin of the frame used for rotation. I think what's important is that the position and velocity (from the Geolocation API) and the acceleration (from the devicemotion event) refer to known points in the body, ideally the same point. Assuming that the body is rigid, this is sufficient to calculate the position, velocity and acceleration of other points in the body under rotation. We don't have any use-cases which which use rigid body kinematics to calculate velocities or accelerations at arbitrary points in the body, and hence require us to specify an origin, but I can see why this would be useful. So in Section 4.3 [1], we should probably update the wording 'must provide the acceleration of the hosting device' to use a specific point. The centre of mass seems like a good choice. Similarly, we should update the Geolocation spec to make clear that the position and velocity there refer to this same point. [1] http://dev.w3.org/geo/api/spec-source-orientation.html#devicemotion Thanks, Steve
Received on Tuesday, 5 July 2011 12:40:09 UTC