New function to get the center of a tile

[jenningsanderson]

Have written this helper function a few times now, perhaps it's helpful to others to include here?

@batpad ?

[honjo2]

function tileToCenterPoint(tile) {
    var bbox = tileToBBOX([tile[0]+.5, tile[1]+.5, tile[2]]);

    return {type: 'Point',
        coordinates: [
            bbox[0],
            bbox[3]
        ]
    };
}

[jenningsanderson]

@honjo2 Wow.

So the latitudes are slightly different between these two versions of the script, I imagine that your version is actually more true given that my version simply averages the min/max.

[bhousel]

I have to admit - I would never have thought to try it that way. 👏

[jenningsanderson]

Tile:

02001021130033300

Bbox:

 {"type":"Polygon","coordinates":[[[-166.212158203125,65.18648824110723],[-166.212158203125,65.18764086352971],[-166.20941162109375,65.18764086352971],[-166.20941162109375,65.18648824110723],[-166.212158203125,65.18648824110723]]]}

Original Way (avg. min/max):

{"type":"Point","coordinates":[-166.21078491210938,65.18706455231847]}

New way (tile x,y + 0.5):

{"type":"Point","coordinates":[-166.21078491210938,65.18706455858751]}

FeatureCollection of the three...

{"type":"FeatureCollection", "features" : [
  {"type":"Feature", "properties":{"type":"bbox"},"geometry":
  {"type":"Polygon","coordinates":[[[-166.212158203125,65.18648824110723],[-166.212158203125,65.18764086352971],[-166.20941162109375,65.18764086352971],[-166.20941162109375,65.18648824110723],[-166.212158203125,65.18648824110723]]]}},
  {"type":"Feature", "properties":{"type":"avg min/max"},"geometry":
  {"type":"Point","coordinates":[-166.21078491210938,65.18706455231847]}},
  {"type":"Feature", "properties":{"type":"tile x,y +0.5"},"geometry":
  {"type":"Point","coordinates":[-166.21078491210938,65.18706455858751]}}
]}

Loading ^ into QGIS, I'm inclined to say that averaging the min/max is actually slightly more accurate when considering the center of a tile as a point on the ground.... though a tile itself should never really be considered a square on the ground... so whichever computation is faster (likely @honjo2 ) seems like the 🥇