annotations/Azaion.Common/Extensions/GeoUtils.cs

namespace Azaion.Common.Extensions;

public static class GeoUtils
{
    private const double EARTH_RADIUS = 6378137;

    public static (int x, int y) WorldToTilePos(double lat, double lon, int zoom)
    {
        var latRad = lat * Math.PI / 180.0;
        var n = Math.Pow(2.0, zoom);
        var xTile = (int)Math.Floor((lon + 180.0) / 360.0 * n);
        var yTile = (int)Math.Floor((1.0 - Math.Log(Math.Tan(latRad) + 1.0 / Math.Cos(latRad)) / Math.PI) / 2.0 * n);
        return (xTile, yTile);
    }

    public static (double lat, double lon) TileToWorldPos(int x, int y, int zoom)
    {
        var n = Math.Pow(2.0, zoom);
        var lonDeg = x / n * 360.0 - 180.0;
        var latRad = Math.Atan(Math.Sinh(Math.PI * (1.0 - 2.0 * y / n)));
        var latDeg = latRad * 180.0 / Math.PI;
        return (latDeg, lonDeg);
    }

    public static (double minLat, double maxLat, double minLon, double maxLon) GetBoundingBox(double centerLat, double centerLon, double radiusM)
    {
        var latRad = centerLat * Math.PI / 180.0;

        var latDiff = (radiusM / EARTH_RADIUS) * (180.0 / Math.PI);
        var minLat = Math.Max(centerLat - latDiff, -90.0);
        var maxLat = Math.Min(centerLat + latDiff, 90.0);

        var lonDiff = (radiusM / (EARTH_RADIUS * Math.Cos(latRad))) * (180.0 / Math.PI);
        var minLon = Math.Max(centerLon - lonDiff, -180.0);
        var maxLon = Math.Min(centerLon + lonDiff, 180.0);

        return (minLat, maxLat, minLon, maxLon);
    }
}