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<map-meta>

The <map-meta> element is an extended HTML meta element, for use in Web maps.

Attributes​

name​

The name attribute identifies the type of metadata that is being set. Possible values of name related to maps include:

NameDescription
projectionSet the projection for the document
extentDefine the bounds of the document in terms of corner position keywords and axis names, potentially combined with a zoom value if necessary (depending on coordinate system).
csIdentifies the default coordinate reference system of coordinate strings found in the document.
zoomSpecify the zoom range min, max and default zoom value for displaying the document contents. The 'native' zoom range of templated map content is specified by the min/max attributes of associated zoom inputs. If templated content is not described by associated zoom input min/max/value attributes, the values specified in a <map-meta name=zoom> will be used as fallback, if it exists. If no <map-meta name=zoom> exists, the corresponding min/max values from the projection will be used.

content​

namecontent value
projectionA case-sensitive projection name, or a custom projection name
extent((position keyword)-(axis name)=(axis value)(,))4(,)(zoom=(zoom value))0,1
csA case-sensitive coordinate system abbreviation.
zoom(min=minimum zoom value,max=maximum zoom value,)(value=current zoom value)
Content categoriesMetadata content
Permitted contentNone, it is an empty element.
Tag omissionWhile the HTML <meta> element is a void element, the polyfill <map-link> must have an end tag.
Permitted parentsInline: the <layer-> element. In a MapML document: the <map-head> element.
Implicit ARIA roleNo corresponding role
Permitted ARIA rolesNo role permitted
DOM interfaceHTMLMetaElement extension

Examples​

Setting zoom​

Using the <map-meta> element to specify the native zoom and fallback zoom range for a <map-feature>. The coordinate encoding is narrowly determined for the feature, by the <map-geometry cs="gcrs"> attribute, which tells the polyfill how to parse and process strings of coordinates found in descendant <map-coordinates> elements.

<layer- label="Favourite Restaurant" checked>
  <map-meta name="projection" content="OSMTILE"></map-meta>
  <map-meta name="zoom" content="min=0,max=22,value=3"></map-meta>
  <map-feature>
    <map-featurecaption>Big Daddy's Crab Shack</map-featurecaption>
      <map-geometry cs="gcrs">
          <map-point>
            <map-coordinates>-75.690276 45.41868</map-coordinates>
          </map-point>
      </map-geometry>
  </map-feature>
</layer->

Setting extent​

Using the <map-meta> element to establish the pcrs (easting,northing) extent of a map layer, the coordinates of which are encoded as gcrs pairs. 

<layer- label="Favourite Restaurant" checked>
  <map-meta name="projection" content="OSMTILE"></map-meta>
  <map-meta name="zoom" content="min=0,max=22,value=3"></map-meta>
  <map-meta name="extent" content="top-left-easting=-8433179, top-left-northing=5689316, bottom-right-easting=-8420968,bottom-right-northing=5683139"></map-meta>
  <map-feature>
    <map-featurecaption>Big Daddy's Crab Shack</map-featurecaption>
      <map-geometry cs="gcrs">
          <map-point>
            <map-coordinates>-75.690276 45.41868</map-coordinates>
          </map-point>
      </map-geometry>
  </map-feature>
</layer->

Fallback cs for <map-geometry>​

Using the <map-meta> to specify a fallback coordinate encoding for geometries in the layer. The encoding of the coordinates is identified by the use of the <map-meta name="cs" content="gcrs"> element. Such a declaration tells the polyfill how to parse and process any coordinates that don't have an ancestor <map-geometry cs=""> coordinate encoding declaration. Note that the zoom level at which the feature should be displayed is not specified, nor the extent. Both values will fall back to the default values for the projection. 

<layer- label="Favourite Restaurant" checked>
  <map-meta name="projection" content="OSMTILE"></map-meta>
  <map-meta name="cs" content="gcrs" ></map-meta>
  <map-feature>
    <map-featurecaption>Big Daddy's Crab Shack</map-featurecaption>
      <map-geometry>
          <map-point>
            <map-coordinates>-75.690276 45.41868</map-coordinates>
          </map-point>
      </map-geometry>
  </map-feature>
</layer->

Default metadata​

Allowing all metadata values to default to those of the map's projection. The feature will be displayed at all zoom levels, and the coordinates are by default interpreted to be gcrs (longitude latitude). The extent of the layer defaults to that of the projection.

<layer- label="Favourite Restaurant" checked>
  <map-feature>
    <map-featurecaption>Big Daddy's Crab Shack</map-featurecaption>
      <map-geometry>
          <map-point>
            <map-coordinates>-75.690276 45.41868</map-coordinates>
          </map-point>
      </map-geometry>
  </map-feature>
</layer->

Specifications​

Specification
MapML meta element
HTML meta element

Requirements​

Need to be documented.

See Also​