On the wire to hard wire my scanner there is a label that reads "For POSITIVE ground, attach the black wire to the negitive wire on the battery and the red wire to the chassis. For NEGITIVE ground attach the red wire to the positive terminal on the battery and the black wire to the chassis."

Whats the difference and which is better?

 

gonna go out on a limb here and say the positive ground is for a positive ground system.. kinda like our 1930 model A ford, is a positive ground system where literally the positive is grounding the car..

 

Older Mack trucks and a lot of European autos use a positive ground . All American autos now use Negative ground .

 

All correct. It's nice that they provide those instructions, but for the vast majority of US installations, they are useless.

It does tell you that the scanner has it's chassis isolated from power ground though, which is interesting.

As has been noted, just wire it negative ground. Positive ground causes more chassis corrosion and that's why it was abandoned. You may have noticed over the years that the positive terminal of a battery tends to corrode more than the negative in an atmospheric environment.

Similar things are actually done using various metals on metal ship hulls using "sacrificial anodes" that get worn away to minimize corrosion of the hull plates.

Here's a wiki on that if you're interested: http://en.wikipedia.org/wiki/Sacrificial_anode

 

I need to bolt some of those to my truck frame.

 

ya they have those on civilian boats as well. their little aluminum fins that bolt to the stern drive above the prop. I never could figure out THAT works. but it does. after awhile u gotta replace them with a new fin.