Mike, Not wanting to put words in Ron's mouth, but: the focal point of the camera IS the location - everything else is "relative". The numbers are smaller, the calculations are simpler and the data load is lighter if you use a local (frame of) reference system. Surveyors have known this for centuries.;-)
Cheers AlanK -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Mike Liebhold Sent: Saturday, 29 August 2009 9:35 AM To: Ron Lake Cc: geojson; [email protected]; GeoRSS Subject: Re: [Geowanking] [georss] [Geojson] simple 3D geocode for AR 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?) >>>> >>>> >>>> _______________________________________________ >>>> Geojson mailing list >>>> [email protected] >>>> http://lists.geojson.org/listinfo.cgi/geojson-geojson.org >>>> >>>> >>> _______________________________________________ >>> georss mailing list >>> [email protected] >>> http://lists.eogeo.org/mailman/listinfo/georss >>> _______________________________________________ >>> georss mailing list >>> [email protected] >>> http://lists.eogeo.org/mailman/listinfo/georss >>> >>> >> _______________________________________________ >> georss mailing list >> [email protected] >> http://lists.eogeo.org/mailman/listinfo/georss >> _______________________________________________ >> georss mailing list >> [email protected] >> http://lists.eogeo.org/mailman/listinfo/georss >> >> >> >> > > > _______________________________________________ Geowanking mailing list [email protected] http://geowanking.org/mailman/listinfo/geowanking_geowanking.org _______________________________________________ Geowanking mailing list [email protected] http://geowanking.org/mailman/listinfo/geowanking_geowanking.org
