gorshkov-leonid/geo-tricks.md

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geo-tricks.md

Slippy map and EPSG3857. How to get SW / NE coordinates of tile.

        // 8 / 85 / 154
        const z = 8
        const x = 85
        const y = 154
        const x0 = (x / Math.pow(2.0, z)) * 360 - 180;
        const y0 = 360 / Math.PI * Math.atan(Math.exp((180 - (y / Math.pow(2.0, z)) * 360) * Math.PI / 180)) - 90;
        const x1 =  (x + 1) / Math.pow(2.0, z) * 360 - 180;
        const y1 = 360 / Math.PI * Math.atan(Math.exp((180 - ((y + 1) / Math.pow(2.0, z)) * 360) * Math.PI / 180)) - 90;
        console.log([x0, y0], [x1, y1])