Change LatLon of Point with Zoom

[wipfli]

By default, point text labels have fixed LatLon coordinates which are constant across zoom levels. However, the ideal placement can depend on the zoom level.

I would like to move labels of countries depending on the zoom level. This requires that I can configure the LatLon of a Point depending on the zoom level. Are there any options to do this in Planetiler?

[msbarry]

There isn't a built in way to do this, but you could emit distinct separate features for each zoom level. Something like:

for (int z = 1; z <= 14; z++) {
  var geom = computePointAtZoom(z);
  features.geometry(layer, geom).setZoomRange(z)... setup feature
}

Maybe there could be some more succinct way using the z or m coordinate of jts point features, but this approach should work today.

[wipfli]

Thanks for the suggestion. I might have a something wrong in the following code snippet since it does not produce a point feature in the output tile. Do you see anything obvious?

  @Override
  public void processFeature(SourceFeature sourceFeature, FeatureCollector features) {
      double longitude = 0.0;
      double latitude = 0.0;
      Coordinate coordinate = new Coordinate(longitude, latitude);
      Point point = GeoUtils.JTS_FACTORY.createPoint(coordinate);

      features.geometry("country", point)
        .setZoomRange(0, 15)
        .setAttr("hello", "world");

[msbarry]

The geometry needs to already be projected into "world web mercator" coordinates where 0,0=top left, and 1,1=bottom right. There's a latLonToWorldCoords(geometry) utility for this, so you could do:

Point point = GeoUtils.latLonToWorldCoords(GeoUtils.JTS_FACTORY.createPoint(coordinate));

[wipfli]

That worked. Thank you!

[1ec5]

This sounds like something that a MapLibre stylesheet would have better control over, especially if the map can be rotated and/or tilted or if the font can vary.

[wipfli]

I can't argue with that for variable fonts and map orientation. But if you know the font then you can optimize for a default orientation. It is actually quite fun to move labels around by hand. Maybe I can share a demo at some point...