def coordinate(i, j)
      x = @pos.x + (i * @delta_col * @cosines[0]) + (j * @delta_row * @cosines[3])
      y = @pos.y + (i * @delta_col * @cosines[1]) + (j * @delta_row * @cosines[4])
      z = @pos.z + (i * @delta_col * @cosines[2]) + (j * @delta_row * @cosines[5])
      Coordinate.new(x, y, z)
    end
def coordinate(i, j)
      x = @pos.x + (i * @delta_col * @cosines[0]) + (j * @delta_row * @cosines[3])
      y = @pos.y + (i * @delta_col * @cosines[1]) + (j * @delta_row * @cosines[4])
      z = @pos.z + (i * @delta_col * @cosines[2]) + (j * @delta_row * @cosines[5])
      Coordinate.new(x, y, z)
    end
Calculates the cartesian coordinate of the given pixel index pair.

 @param [Integer] i the image column index
 @param [Integer] j the image row index
 @return [Coordinate] the cartesian coordinate of the pixel