Radar guns are calibrated with tuning forks, as far as I know Georgia calibrates for 33 mph and the other is for 66mph. They "ring" each fork then dial them both in to the correct mph. Halfway between 33 and 66 is 49.5 mph, a difference of 16.5. Add that 16.5 to 66 and that will give you the highest accurate amount of mph the radar gun is calibrated for. Ironically 66 + 16.5 is 82.5 and the dude that had the jury trial was charged for 83 mph. Anything above that amount is not accurate and the higher it goes the more error there is. That is information coming from a retired officer. Sources on the internet say one is for ground speed and the other is for patrol car speed. It is all different for the different radar bands used and stationary radar is calibrated differently than moving radar.Originally Posted by marcos713
Other laws (those "14" documents, etc.):
1) One, the gun has to be certified with an annual or semi annual inspection. Every single one has to be sent off. It has to be done by a 3rd party/independent, not the department themselves. This is not always done. They may only send off a few.
2) The gun has to be calibrated daily and it's recorded by the officer each time. Hand written, date and time of calibration.
3) The road the radar is being used on MUST be certified by the FCC. Each county/city has a huge book with all the roads that are certified for radar use. If that road isn't on the list then it legally can't be used on it.
4) The department has to licensed by the Department of Public Safety to use the radar/laser. They pay for an annual permit. If they don't renew that permit then they lose all radar use privileges and it takes months to go through the process again. (I lived in a county that lost their permit for over 3 months because they failed to renew it in a timely manner, good times.) It's not just that the department that is certified, each and every officer has to be certified and registered under that department. If it's a new or transfered officer there is a chance he is not registered with that department.
5) Line of site has to be a minimum of 500' to prevent entrapment. 500 feet on an interstate isn't far at all but 500 feet in congested area where the speed limit is only 25 to 45 is a considerable distance.
6) It's unlawful for them to ticket you with radar if the slope is greater than 7.0% grade downhill. This is 7 feet down for every 100 feet forward. It is much steeper than you think. If you've seen the signs in the mountains that say "12% grade downhill, trucks use lower gear" then you know what I mean.
7) Just because there is a speed limit sign does not mean it instantly applies. You have 300 feet in an unincorporated area and 150 feet in an incorporated area past the sign before that change of speed limit legally applies to you.
8) An officer can not be within 500 feet of a speed detection device warning sign.
I should do a complete write up including the codes they refer too...
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