Re: ISSUE-31 relative points?

Hi Alex,

Q: Would this be a valuable addition to the spec?

YES, I believe it is extremely important to include relative in a frame 
of reference. This is

Q: Can we think of use cases that would benefit?

Using a system in which the detection and the display devices are 
decoupled. Point display/output device in any direction to detect and 
display objects (moving or fixed) relative to the viewing system, in 
another or place (e.g., by "looking through" the walls and) knowing the 
position of the camera is relative to the display/output device. Frame 
of Reference is important to correctly position (a) object of interest 
relative to both (b) capture/detection device (e.g, remote camera) and 
(c) the display/output device.

Such a system would be relevant for

#1 games
#2 surveillance
#3 Personal area "health" networks (e.g., a patient monitoring device, a 
display in another part of the room)
#4 Navigation
     imagine using the FOR feature to locate/navigate to an object 
(e.g., a phone) rather than a place as long as the user is positioned in 
a zone (e.g., a building)


Q: What about indoor tracking of POIs?

IMHO, this is an extremely important topic but I suspect we don't need 
to treat it separately from any relative positioning use case. The 
support for FOR must be in the specification. Then, we can use it to 
work backwards from indoor positioning.


Q: What about vehicle/pedestrian entrances for the mapping crowd?

Q: Can we put the relative information in the data model and then let 
systems back out the actual coordinates for efficiency? Then if you find 
(don't know how yet) that an update is necessary you can re-calculate.

Yes, my opinion is this is the optimum (best) scenario.

I look forward to hearing the views of others.

Christine

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cperey@perey.com
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On 6/10/11 6:17 PM, Alex Hill wrote:
> I think we need to have a discussion about what "relative" positioning 
> means.
> One example I have seen is in CityGML where building geometry is 
> described in meters relative to an anchor point.
> However, I'm not sure what such a system for describing polygons, etc. 
> would buy us in the POI spec.
> I tend to think that we intended relative positioning to facilitate 
> things like the following:
> <pois>
> <poi id="frame_of_reference">
> <location>
> <!-- some reference to a moving vehicle a building or any arbitrary 
> frame of reference (not just coords but orientation would be nice) -->
> </location>
> </poi>
> <poi id="alex">
> <location>
> <!-- some value calculated within that frame of reference (WiFi 
> tracking, etc.)  in something not WGS84 -->
> <point srsName="urn:ogc:def:crs:EPSG:6.6:4979" srsDimensions="3">
> <pos>10023.123 1234.123 666.66</pos> <!-- lets say this is mm for now -->
> </point>
> </location>
> <relation type="relative-to" id="#frame_of_reference"/>
> </poi>
> </pois>
>
> Is that appropriate, or do we want something where each individual 
> georeference can specify a relative frame of reference?
>
> <pois>
> <poi id="frame_of_reference">
> <location>
> <point relative_to="#frame_of_reference" 
>  srsName="urn:ogc:def:crs:EPSG:6.6:4979" srsDimensions="3">
> <pos>10023.123 1234.123 666.66</pos> <!-- lets say this is mm for now -->
> </point>
> <!-- some reference to a moving vehicle a building or any arbitrary 
> frame of reference (not just coords but oriented would be nice) -->
> </location>
> </poi>
> <poi id="alex">
> <location>
> <point relative_to="#frame_of_reference" 
>  srsName="urn:ogc:def:crs:EPSG:6.6:4979">
> </location>
> </poi>
> </pois>
>
> Sorry if this is not "correct", but I'm more concerned about the 
> spirit of this than the syntax.
> Would this be a valuable addition to the spec?
> Can we think of use cases that would benefit?
> I suspect the AR advocates can.
> What about indoor tracking of POIs?
> What about vehicle/pedestrian entrances for the mapping crowd?
> Can we put the relative information in the data model and then let 
> systems back out the actual coordinates for efficiency?
> Then if you find (don't know how yet) that an update is necessary you 
> can re-calculate.
> Perhaps what you have above ends up looking like:
> <location>
> <point>
> <pos>-72.123 34.1234 100.7</pos> <!-- the non-relative position of 
> this point in WGS84 -->
> </point>
> <point relative_to="#frame_of_reference" 
>  srsName="urn:ogc:def:crs:EPSG:6.6:4979" srsDimensions="3">
> <pos>10023.123 1234.123 666.66</pos> <!-- lets say this is mm for now -->
> </point>
> <!-- some reference to a moving vehicle a building or any arbitrary 
> frame of reference (not just coords but oriented would be nice) -->
> </location>
>
>
> Alex Hill Ph.D.
> Postdoctoral Fellow
> Augmented Environments Laboratory
> Georgia Institute of Technology
> http://www.augmentedenvironments.org/lab
>