Software for reducing manual theodolite observations

I have a set of survey data as a baseline traverse with side observations done using a manual theodolite (my elderly Cooke Tavistock). This is mostly horizontal and vertical circle readings plus chained measurements for the legs of the traverse. I do not have distance measurements for the side shots. In short a standard triangulation survey.

I tried to process this using COPAN as "field data" but it seems to complain about the lack of SD measurements.

Here is a trivial example with single baseline 1 to 2 and two side observations. I can obviously reduce this trivial example by hand. Copan objects to the to=3 line, I think because of lack of SD (the error isn’t clear)

at= 1   az=180.0    HC=0.0
    to=2    HC=165.4351 VC=90.0 SD=7.65 
    to=3    HC=39.1521  VC=90.0 
    to=4    HC=51.1922  VC=90.0 
at= 2   ref=1   HC=297.1256
    to= 3   HC= 334.0115    VC=90.0 
    to=4    HC=339.1919 VC=90.0 
end=close

Is there any trick to reducing this?