How to select 3 position lines

I explained the effects of the included angles of 3 position lines or of the distances between the observer and the objects upon the accuracy of ship's position. And I also compared the accuracy of ship's position by 3 position lines with that by 2 position lines. So it will be solved how to decide 3 position lines to obtain the best accuracy of ship's position. Now I studied each accuracy of ship's position by 3 position lines having equivalent random error and different one. The former, I believe, will be useful to select 3 heavenly bodies on nautical astronomy, and the latter to select 3 objects for Cross Bearing method.