CODEWITHSUNDEEP
zoomingopenlayersopenlayers-5
svoop
svoop

Reputation: 3454

Lock zoom of WMTS tiles in OL

I'm using tiles from IGN Géoportail WMTS to render a background map as outlined in this example:

var resolutions = [];
var matrixIds = [];
var proj3857 = getProjection('EPSG:3857');
var maxResolution = getWidth(proj3857.getExtent()) / 256;

for (var i = 0; i < 18; i++) {
  matrixIds[i] = i.toString();
  resolutions[i] = maxResolution / Math.pow(2, i);
}

var tileGrid = new WMTSTileGrid({
  origin: [-20037508, 20037508],
  resolutions: resolutions,
  matrixIds: matrixIds
});

var ign_source = new WMTS({
  url: 'https://wxs.ign.fr/pratique/geoportail/wmts',
  layer: 'GEOGRAPHICALGRIDSYSTEMS.MAPS',
  matrixSet: 'PM',
  format: 'image/jpeg',
  projection: 'EPSG:3857',
  tileGrid: tileGrid,
  style: 'normal',
  attributions: '<a href="http://www.geoportail.fr/" target="_blank">' +
    '<img src="https://api.ign.fr/geoportail/api/js/latest/' +
    'theme/geoportal/img/logo_gp.gif"></a>'
});

var ign = new TileLayer({
  source: ign_source,
  opacity: 0.7
});

On zoom level 12, the map shows the details I need:

enter image description here

However, zooming out to zoom level 13, the tiles switch to less details, too few for my use case:

enter image description here

Is there a way to tell OpenLayers to "lock" the tile zoom to 12 while still allowing zooming beyond this threshold rendered by OpenLayers instead of the WMTS?

Or in other words: Let OpenLayers do all the zooming and always get zoom level 12 detail tiles from the WMTS.

Thanks for your help!

Upvotes: 2

Views: 405

Answers (1)

Mike
Mike

Reputation: 17932

This will restrict the tilegrid to zoom level (matrix id) 13:

var tileGrid = new WMTSTileGrid({
  origin: [-20037508, 20037508],
  resolutions: resolutions.slice(13,14),
  matrixIds: matrixIds.slice(13,14)
});

Upvotes: 2

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