Here is the translation:

"Dear,

I use the Jag3D program for the adjustment of both 1D and 2D networks. I have a question to which I couldn't find an answer on the forum. What do the parameters sigma a, sigma b, and sigma c mean?
As far as I understand, if the accuracy of the instrument we use is 1mm, sigma b should have a value of 1. Sigma c is always zero, but what is sigma a? Is it the a priori standard deviation that is by default 1, or is it something else?
If it is, should sigma a be 1? If not, what is it, and where is the a priori standard deviation set?
Thank you."