Re: MapML encoding of video features


Firstly, thanks for moving to a separate thread to discuss this.

1. You’re right. It’s not GeoJSON, though similarly structured - my mistake. 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. Leaflet has a clear tutorial: <>

2. I agree that DOMString is the correct choice for the shape element, c.f. the type attribute for the HTML input element: <>

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?

4. The HTML5 video element already supports metadata tracks, so I propose:
<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.

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.

This is an adaptation of the existing system and follows the precedent established by WebVTT. It leaves the original video file unchanged, adds a separate text-based file for the associated metadata, e.g. subtitles or map presentation, and makes the data accessible to be used in other contexts. In the case of subtitles, the text and timing details can be used and amended by the wider video community for non-web-based solutions.

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: <>, i.e. an HTML display container floating over the map and associated with a location marker. 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.

I look forward to hearing from you.

Rob Smith

Away Team <>
> On 11 Jan 2018, at 20:12, Rushforth, Peter (NRCan/RNCan) <> wrote:
> Hi Rob,
>> I think we should take any further discussion of MapML to a separate thread
> New thread name, as suggested.  I would like to maybe brainstorm a little on how a video element could be marked up and animated according to the motion and view of the sensor
>> The biodome example ... uses GeoJSON tags
> If you view-source on the biodome example, you'll see a MapML feature:
>       <feature><properties><name>Biodome</name></properties><geometry><Point><coordinates>-73.549767 45.559659</coordinates></Point></geometry></feature>
> which is not GeoJSON, its MapML in WGS84. Under the hood, we transform that so that the JavaScript Leaflet.js library can render it as SVG, in fact.  Leaflet needs GeoJSON for that purpose, so the transformation is pretty simple.
>> The area tag co-ordinates are defined in CSS
> Yes, we support the area tag as  fallback for when JavaScript is disabled or whatever.  The custom <layer-> element supports MapML content inline, as in the above example, or served over the network from servers and files. When the custom <map> element's JavaScript runs, if there is a custom <area> child element, it converts the area@coords to a layer/feature in MapML, which then is transformed into a GeoJSON object and then into SVG by the Leaflet engine.  
>> Also, the spec has a typo in the area tag’s shape attribute type, which is incorrectly defined as a boolean and should be an enumeration.
> Fixed, I think. Thanks. I could only find DOMString as being appropriate. DOMTokenList seems to represent a possible array of values, and shape can only take on a single value.
> In OGC Testbed 14 we are hoping to implement a MapML encoding of features which will look a little like the above, but will lean more heavily on existing / well defined markup in HTML.  
>> please let me know if you have any additional comments regarding video geotagging for maps.
> For example, we could think of a video related feature like this:
> <feature itemscope itemtype="">
> <properties><h1 itemprop="name">Search and Rescue Drone flight path 2018-12-22</h1><video itemprop="recording" src="flight-2018-12-22.webm"></video></properties>
> <geometry><LineString><coordinates>-75.6818885 45.40813 -75.6818872 45.408013 -75.6819895 45.4080214 -75.6821553 45.4079933 -75.6822566 45.4079207 -75.6823962 45.4078389 -75.6830192 45.407565</coordinates></LineString></geometry>
> </feature>
> The content of the <feature> element has two parts, the properties and geometry.  Properties is structured as microdata-marked up HTML, and generates a browsing context when activated, like a map balloon for example. Geometry is structured as an OGC simple features geometry, except that the content of <coordinates> could contain certain markup, such as span, a, and possibly others TBD.  The geometry is drawn on the map, according to applied styles.
> Is there a DOM API for video that would allow you to extract coordinates from the frames and animate the 'balloon' containing the video, perhaps? If the balloon browsing context could execute JavaScript, it could leverage that API for custom behaviour.
> Thanks,
> Peter
> Peter Rushforth
> Technology Advisor
> Canada Centre for Mapping and Earth Observation / Earth Sciences Sector
> Natural Resources Canada / Government of Canada
> / 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
> / Tél: 613-759-7915

Received on Monday, 15 January 2018 16:39:21 UTC