I have used a survey grade GPS unit from work before ............ for 25k they work awesome
On a serious note you can use a GPS unit with differential correction like WAAS can get you to sub-meter accuracy which is sufficient for a DG course. The only issue with using a GPS unit is when you have severe elevation. Think Hole 11 at McHose and Hole 6 at Akita’s Run. The only way you can accurately use a GPS unit with severe elevation is with a survey grade unit where you get centimeter vertical and horizontal measurements and do a little post processing to calculate the length of your slope (your straight line distance, tee to pin) by using your rise and run.
"I'm not impressed with aces of any kind. 95% of the time, they're just bad shots that got lucky and happened to hit the chains. Otherwise, they'd have sailed 50' past the hole." ~ Cydisc