The calculation of ionospheric coefficients is not well understood

[7upcyang]

The coefficient of the vertical single-difference ionospheric delay is equal to the average of the two projections. Which literature introduces it? It seems to be difficult for beginners to understand.

rtkpos-ddres- im[i]=(ionmapf(posu,azel+iu[i]*2)+ionmapf(posr,azel+ir[i]*2))/2.0;

I hope you can reply me when you are free.