Christian Willmes wrote:
whats the problem here? Its simple coordiante transformation stuff... or
do I miss something?!
Here's a concrete reformulation of Christian's question, with the simple
stuff written down:
An AR device asks the server: "I know that I am at X,Y,Z position relative
to object A (eg the Eiffel tower); please tell me about features nearby in
rectilinear coordinates relative to A". But the device can also ask "please
tell me about A and the features nearby in WGS84; I'll do the math myself:"
x = 60*nauticalMileToMeter*(longitude(feature) -
longitude(A))*cosine(latitude(A)))
y = 60*nauticalMileToMeter*(latitude(feature)-latitude(A))
z = altitude(feature)-altitude(A)
This is an approximation, but will work well for AR except in the case of
people using their devices from orbit.
--chris
----- Original Message -----
From: "Christian Willmes" <[email protected]>
To: "Mike Liebhold" <[email protected]>
Cc: "Ron Lake" <[email protected]>; "geojson" <[email protected]>;
<[email protected]>; "GeoRSS" <[email protected]>
Sent: Friday, August 28, 2009 6:00 PM
Subject: Re: [Geowanking] [georss] [Geojson] simple 3D geocode for AR
Hi,
whats the problem here? Its simple coordiante transformation stuff... or
do I miss something?!
The device gets the geocoordinates from the web, and computes those using
its own position and orientation to local camera coordinates....
its that simple... I think. ;-)
regards,
Christian
Mike Liebhold schrieb:
Ron Lake wrote:
The most logical coordinate
system for locating such items is a rectilinear coordinate system (x-y-z
frame) centered (origin) at the focal point of the camera.
What's the use case?
In most cases, we probably can assume that the geo-annotations exist
independent of the viewpoint; e.g. a viewer should be able to see the
note attached to a restaurant from any perspective as they pass on a
sidewalk, or drive by.
In that case, we need absolute coordinates, not relative to the camera
perspective.
imho
Mike
Cheers
Ron
-----Original Message-----
From: Mike Liebhold [mailto:[email protected]] Sent: August 28, 2009 2:05 PM
To: Ron Lake
Cc: Joshua Lieberman; [email protected]; geojson; GeoRSS
Subject: Re: [georss] [Geojson] simple 3D geocode for AR
Ron Lake wrote:
The use of geographic coordinates for [location of things in the field
of view relative to the camera] likely does not. [ make sense]
Ron,
This is really counter intuitive, Can you explain what you mean?
- Mike
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Joshua Lieberman
Sent: August 28, 2009 11:03 AM
To: [email protected]
Cc: geojson; GeoRSS
Subject: Re: [georss] [Geojson] simple 3D geocode for AR
In both GeoRSS GML and GeoJSON, some explicit CRS needs to be specified
to use 3-coordinate locations. The simplest one for GeoRSS seems to be
epsg:4979 ( urn:ogc:def:crs:EPSG:4979 ). It would need a slight
modification to support the GeoJSON long-lat encoding. Otherwise use
GeoRSS Simple and the elev property.
e.g.
<georss:elev>346</georss:elev>
<georss:point>42.3234 -173.234134</georss:point>
Well-known text description of 4979
(http://spatialreference.org/ref/epsg/4979/ )
GEOGCS["WGS 84", DATUM["World Geodetic System 1984", SPHEROID["WGS
84",
6378137.0,298.257223563, AUTHORITY["EPSG","7030"]],
AUTHORITY["EPSG","6326"]], PRIMEM["Greenwich",0.0,
AUTHORITY["EPSG","8901"]], UNIT["degree",0.017453292519943295],
AXIS["Geodetic latitude",NORTH], AXIS["Geodetic longitude",EAST],
AXIS["Ellipsoidal height",UP], AUTHORITY["EPSG","4979"]]
Josh
On Aug 28, 2009, at 1:05 PM, Ron Lake wrote:
Sorry my example should have been
<Point id = "P1" CRS = "http://www.blah.bla/standardCRS.xml";>
<coordinates>100 200 150</coordinates>
</Point>
But the argument is the same. Similar encodings can be made in JSON
etc.
R
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Andrew Turner
Sent: August 28, 2009 9:57 AM
To: [email protected]; GeoRSS; geojson
Subject: Re: [georss] [Geojson] simple 3D geocode for AR
Simplest?
Just include a 3rd coordinate in GeoRSS-Simple point or GeoJSON
point.
No, this is not explicitly valid. But you see where that discussion
gets us. Long windy roads of elusive semantic talk (arguably
necessary
in the lon term, but not simple or useable *now*, which is when
people
are building these tools).
If we lose interest without achieving a near term concensus,
developers will just do arbitrary, different solutions. Give them a
simple answer now, even if it makes your strict-validation-only-skin
crawl just a little bit. :)
So I say just do it, and we'll catch up with documenting it as uses
emerge.
Also, KML already supports 3D points.
Andrew
(via mobile)
On Aug 27, 2009, at 4:35 PM, Mike Liebhold <[email protected]> wrote:
A friend wrote me with a request for clarification on a topic we've
discussed many times here, but every time we've approached a
consensus the answer seems elusive.
Many devleopers are starting to create applications for iPhones and
Android phones to view location specific data through the
viewfinder using the -imprecise- capabilities of the built in gps
and compass and applications platforms like Layar.
The question:
What is the -simplest- way to geocode a geoannotation in 3D using
geoRSS/Atom, geojson, KML ....?
(Is there a practical reason why WGS '84 shouldn't be implicit, and
a CRS lookup NOT be required?)
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