Yes we are getting of the time period, but...
I know that British FO use the GPS on flat terrain i.e. desert, by giving the guns cp the FO loc stat. Then using a laser range finder give a correction to the target from their own location. So in effect you are giving a target location as your position then applying a correction. You want to hope the guns cp apply the correction. I see that as a risky business.
Back to TRP..are they worth their value?