function TCoordConverterMercatorOnSphere.LonLat2MetrInternal(const ALl: TDoublePoint): TDoublePoint;
var
  VLonLat: TDoublePoint;
begin
  VLonLat := ALl;
  VLonLat.x := VLonLat.x * (Pi / 180);
  VLonLat.y := VLonLat.y * (Pi / 180);
  result.x := Datum.GetSpheroidRadiusA * VLonLat.x;
  result.y := Datum.GetSpheroidRadiusA * Ln(Tan(PI / 4 + VLonLat.y / 2));
end;

function TCoordConverterMercatorOnSphere.LonLat2RelativeInternal(const XY: TDoublePoint): TDoublePoint;
var
  z, c: Extended;
begin
  Result.x := 0.5 + XY.x / 360;
  z := sin(XY.y * Pi / 180);
  c := 1 / (2 * Pi);
  Result.y := 0.5 - 0.5 * ln((1 + z) / (1 - z)) * c;
end;

function TCoordConverterMercatorOnSphere.Metr2LonLatInternal(const AMm: TDoublePoint): TDoublePoint;
begin
  result.X := (AMm.X / Datum.GetSpheroidRadiusA) * (180 / Pi);

  Result.Y := (AMm.Y / Datum.GetSpheroidRadiusA);
  Result.Y := exp(Result.Y);
  Result.Y := ArcTan(Result.Y);
  Result.Y := (2 * (180 / Pi) * Result.Y) - 90;
end;

function TCoordConverterMercatorOnSphere.Relative2LonLatInternal(
  const XY: TDoublePoint): TDoublePoint;
begin
  Result.X := (XY.x - 0.5) * 360;
  Result.Y := -(XY.y - 0.5) * (2 * PI);
  Result.Y := (2 * arctan(exp(Result.Y)) - PI / 2) * 180 / PI;
end;