topic Re: Any idea to get center coordinate in each tile from basemap? in ArcGIS JavaScript Maps SDK Questions

Any idea to get center coordinate in each tile from basemap?

AyakoSUZUKI — Fri, 21 Jul 2017 11:14:09 GMT

I want to get center coordinate in each tile from basemap.

I am using JS API and I can get origin, level, row and colum.

So I think I can get center point by using math calculation.

But I do not have any idea...

I attached an image to show what I want to know.

Any help would be great!

Re: Any idea to get center coordinate in each tile from basemap?

ThomasSolow — Fri, 21 Jul 2017 14:08:08 GMT

Here's a sample that draws each tile's extent as the tiles update (ie as you zoom in and out)

JS Bin - Collaborative JavaScript Debugging

You could draw the center of each extent rather than the extent itself.

Re: Any idea to get center coordinate in each tile from basemap?

AyakoSUZUKI — Sun, 12 Dec 2021 00:48:45 GMT

This is a great idea!

However, I need to get center point when I create basemap.

I am tyring to create custom basemap layer by extending TiledMapServiceLayer class.

Because the tile service uses different schema, I concluded I need center point to retrieve tiles.

The snippet below is what I've done so far.

var CustomLayer = declare([TiledMapServiceLayer], {
  constructor: function(){
    this.spatialReference = new SpatialReference(...);
    this.initialExtent = (this.fullExtent = new Extent(...));

    this.tileInfo = new TileInfo({
      rows: 256,
      cols: 256,
      dpi: 96,
      format: "png",
      compressionQuality: 90,
      origin: {x: -2.0037508342787E7, y: 2.0037508342787E7},
      spatialReference: {wkid: 102100},
      lods: [
        { level: 0, resolution: 156543.03392800014, scale: 5.91657527591555E8 },
        { level: 1, resolution: 78271.51696399994, scale: 2.95828763795777E8 },
        .....
      ]
    });

    this.loaded = true;
    this.onLoad(this);
  },

  getTileUrl: function(level, row, col) {
    /* need to get center point in each tile to create request url*/
    return url;
  }
});‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Re: Any idea to get center coordinate in each tile from basemap?

ThomasSolow — Mon, 24 Jul 2017 19:21:08 GMT

Hmm, that's a harder problem. Thinking about it, there should be a way to figure out of the center of each tile if you know the row, column, origin, and resolution.

Speaking generally, I would think that the x, y would be (col + .5) * resolution, (row + .5) * resolution (assuming the tile coordinates are 0 based). But I'm unsure how the "tile grid" is oriented compared to the web mercator x, y axis. Maybe you can figure this out based on the origin that is passed into the TileInfo.

I'll take a look at the source code and see if I can find an example of this being done.

Re: Any idea to get center coordinate in each tile from basemap?

anweshponugumati2 — Mon, 31 Jan 2022 13:02:10 GMT

Hi Any luck with solution for this?

Re: Any idea to get center coordinate in each tile from basemap?

JohnGrayson — Mon, 31 Jan 2022 15:57:38 GMT

If using BaseTileLayer you can use the getTileBound() method.