It could, hypothetically, work at such a small distance if you're very precise. Longer distances would be better, but unless each line covers a quarter of the sphere's circumference you wouldn't get a triple right triangle, just a triangle with an interior angle of greater than one hundred eighty degrees.
This is because the smaller the distance on a sphere, the closer to planar the surface between points is. So the smaller the distance on the Earth, the smaller the total interior angle of the triangle, down to one hundred eighty degrees, or very near to it.