XAML-Map-Control/MapControl/Shared/EquirectangularProjection.cs

using System;
#if WPF
using System.Windows;
using System.Windows.Media;
#elif AVALONIA
using Avalonia;
#endif

namespace MapControl;

/// <summary>
/// Equirectangular Projection - EPSG:4326.
/// Equidistant cylindrical projection with zero standard parallel and central meridian.
/// See "Map Projections - A Working Manual" (https://pubs.usgs.gov/publication/pp1395), p.90-91.
/// </summary>
public class EquirectangularProjection : MapProjection
{
    public const string DefaultCrsId = "EPSG:4326";

    public EquirectangularProjection() // parameterless constructor for XAML
        : this(DefaultCrsId)
    {
    }

    public EquirectangularProjection(string crsId)
    {
        IsNormalCylindrical = true;
        CrsId = crsId;
    }

    public override Matrix RelativeTransform(double latitude, double longitude)
    {
        return new Matrix(1d / Math.Cos(latitude * Math.PI / 180d), 0d, 0d, 1d, 0d, 0d);
    }

    public override Point LocationToMap(double latitude, double longitude)
    {
        return new Point(
            EquatorialRadius * Math.PI / 180d * longitude,
            EquatorialRadius * Math.PI / 180d * latitude);
    }

    public override Location MapToLocation(double x, double y)
    {
        return new Location(
            y / EquatorialRadius * 180d / Math.PI,
            x / EquatorialRadius * 180d / Math.PI);
    }
}