RE: MapML encoding of video features

Hi Rob,

As a colleague of mine pointed out, given that a text track can accept HTML markup, perhaps, depending on what markup is allowed, that HTML could (in the future) include a <map> element. The map could be an overlay on the video, and it could be navigated by the  changing location information in the text track, in sync with the video.  That could be another option, of course HTML doesn't yet support the proposed <map> element per our community group.  Here's hoping :-).

Thanks,
Peter


Peter Rushforth

Technology Advisor
Canada Centre for Mapping and Earth Observation / Earth Sciences Sector
Natural Resources Canada / Government of Canada
peter.rushforth@canada.ca / Tel: 613-759-7915

Conseiller technique
Centre canadien de cartographie et d’observation de la Terre / Secteur des sciences de la Terre
Ressources naturelles Canada / Gouvernement du Canada
peter.rushforth@canada.ca / Tél: 613-759-7915


> -----Original Message-----
> From: Rushforth, Peter (NRCan/RNCan) [mailto:peter.rushforth@canada.ca]
> Sent: January 15, 2018 2:52 PM
> To: Rob Smith <rob.smith@awayteam.co.uk>
> Cc: public-sdwig@w3.org
> Subject: RE: MapML encoding of video features
> 
> Hi Rob,
> 
> > 1. ... It might help others to more easily understand these features if you
> made a sequence of simple examples, e.g. how to add a marker with a label,
> how to draw a path, how to draw basic shapes, etc.
> 
> Yes, that would be ideal.  I started writing tutorials with "how to make a map
> with MapML":  http://www.nrcan.gc.ca/earth-

> sciences/geography/topographic-information/free-data-geogratis/geogratis-
> web-services/18875 and I intend to extend it as time and resources allow.  I
> was thinking that since vector MapML is more experimental at this point, that
> after Testbed 14 is done will be a good opportunity to extend the
> documentation.  I would like to get other contributors involved, and I hope
> that I can bring the client code base closer to compatibility with the just-
> released Leaflet 1.3.0, in the further hope that we can find some common
> opportunities with the Leaflet.js core contributors.
> 
> > 3. Is it possible to draw a circle in non-CSS pixel units with MapML? For
> example, how can I draw a 10-metre radius circle around the Greenwich
> Observatory at 51.48N, 0.00E?
> 
> The intent of MapML vectors is to rely on OGC Simple Features for the
> geometry model.  As such, I believe (anyone with better knowledge than this
> please correct me) that a circle is easily represented by a Polygon with the
> vertexes arranged approximately in a circle. So, in order to enable simple
> client-side creation of circles as features using WGS84, we would have to
> either extend the standard or do it imperatively, via a attribute/property/
> API method on the <layer> element, or something similar.  Certainly worth
> discussing!  Maybe you could join the Maps for HTML cg and we can design
> something through email over there.
> 
> > 4. The HTML5 video element already supports metadata tracks, so I
> propose:
> <div>
> <h1>Search and Rescue Drone flight path 2018-12-22</h1>
> <video width="640" height="360">
>     <source src="flight-2018-12-22.webm” type=“video/webm”>
>     <track src=“flight-2018-12-22.meta” kind=“metadata">
>     Your browser does not support HTML5 video.
> </video>
> </div>
> 
> where the flight-2018-12-22.meta file contains the associated map
> annotation details, e.g. draw a line using a list of path co-ordinates at given
> times, in a suitable standard format.
> 
> Yes, I think that would be ideal. I see that tracks can contain structured info,
> including html markup or json objects. (Why not MapML?). The important
> thing for such tracks would be to relate sequences from the video / audio to
> locations on a map. The task then is to define a reliable way to do that.  If the
> video/audio element is (part of) a property of a MapML feature, that is a
> predefined scope for the relationship, no? That is to say, that a video in an
> HTML document, despite that it might be have a track that contains
> coordinates of a path, how(why?) would you create an API to access that info
> if maps weren't part of HTML?  OTOH, if maps are built-in to HTML, you could
> associate the video/audio track to maps in different ways, I think.  I think this
> is fertile ground.
> 
> > I’m unclear about the aim of your ‘balloon’ example. Which problem is it
> trying to address? Firstly, the video-related feature does not link the path co-
> ordinates to any timing information in the video. I presume that the ‘balloon’
> is equivalent to a Leaflet Popup: http://leafletjs.com/reference-

> 1.3.0.html#popup, i.e. an HTML display container floating over the map and
> associated with a location marker.
> Yes I used 'balloon' to mean what is described as 'popup' by leaflet.
> 
> > Assuming I’ve understood correctly so far, the video and map elements will
> be competing for the same display space, as a significant part of the map will
> be obscured by the video near the point of interest, which seems
> counterproductive.
> > Firstly, the video-related feature does not link the path co-ordinates to any
> timing information in the video.
> 
> I guess there are different modes in which to manage the relationship
> between video and map.  One is as a balloon/popup.  In that case the balloon
> hides some of the map, yes. But it has the advantage of pointing to a spot.
> Maybe the track metadata could guide where it points to as the video/audio
> plays. Another is like we see in the Leaflet documentation, where a video is
> treated like an image overlay feature (static).  I don't know if there's any
> value in georeferenced track info  /metadata in that use case.  What do you
> think? Finally, maybe you could control the map via its api using track location
> information as the video/audio plays. I think this is more of a scripting use
> case, but you could probably figure out how to do it declaratively too.
> 
> Interesting discussion!
> 
> Thanks,
> Peter
> 
> 
> Peter Rushforth
> 
> Technology Advisor
> Canada Centre for Mapping and Earth Observation / Earth Sciences Sector
> Natural Resources Canada / Government of Canada
> mailto:peter.rushforth@canada.ca / Tel: 613-759-7915
> 
> Conseiller technique
> Centre canadien de cartographie et d’observation de la Terre / Secteur des
> sciences de la Terre
> Ressources naturelles Canada / Gouvernement du Canada
> mailto:peter.rushforth@canada.ca / Tél: 613-759-7915

Received on Tuesday, 16 January 2018 17:13:33 UTC