Transmission Line Earthing

Dear Sirs,

It appears that counterpoise wires are used parallel to the transmission line in order to reduce the earthing resistance and also the potential between the conductor and tower top.

But countepoises are also used at 45 degrees to the transmission line, and also at 90 degrees to the alignment of the transmission line. Why?

In case of single counterpoise wire, parallel counterpoise wires are also used?Also, where are radial and ring-type of counterpoises used?

If the tower footing resistance is not achieved by say 25 metres of counterpoise, then the length is increased to 50 metres or 70 metres?

Best Regards,