For the ground rods to check voltage in ground, try one copper and one steel rod and see what happens. If you get negative voltage, switch leads on the voltmeter to the rods.

When I found over 2volts, I had a copper rod in the ground about 2 feet deep and about 1 foot sticking out. I put one lead on the volt meter to that. Then I put the other lead of the voltmeter with an "extension cord" connected to the steel rod and I poked around on the ground up to several feet away from the copper rod until I found the highest voltage.

If you get 2 volts you're doing great. If you get 3+, that is phenomenal.