I have a question regarding to position and location engine. I have conducted several experiments and I realized that the position of the tag works best when the tag is in the middle. However, I do not understand the reason. Why it should works best in the middle?
it gives the position everywhere even in out of the box, so there is no problem with trilateration. So one assumption is that the ranging between Anchor and tag is less noisy, but why in the middle?

The middle is better due to GDOP, rather than the range errors. It is a trilateration/geometry effect.

Hi Zoran;

Could you explain more? what is GDOP?


I am asking this question because I also measure the noise in ranging measurements from an anchor every 0.5 meter to 3 meter. The result I attached in the picture. The error in ranging is small when the tag is very close then it goes up as you get further away, however in the middle the noise drops at the middle. This is independent from trilateration. I do not have any idea why?