Cheap GPS unit with ~3 ft or better accuracy, used or otherwise.

All,

I'm wanting to mark out some points on my property based on lat/lon, and need a GPS unit I can carry around that will give me a ~3 ft or better accuracy under some tree cover (lot has a decent amount of trees.) I can carry my laptop or phone to run software that will do post-processing. Ideally something $300 or less (used is fine.)

Just need to know recommendations for a complete solution (I saw a lot of items on ebay for Trimble and others, but, don't know if they have all of the parts I need, etc.)

Thanks!

Nate

 

Commercial and military gps perhaps but not consumer / civilian gps. Military I remember reading years back is into mm accuracy for different types of gps controlled equipment.
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The United States government currently claims 4 meter RMS (7.8 meter 95% Confidence Interval) horizontal accuracy for civilian (SPS) GPS. Vertical accuracy is worse. Mind you, that's the minimum. Some devices/locations reliably (95% of the time or better) can get 3 meter accuracy.Dec 10, 2012

See Document "GLOBAL POSITIONING SYSTEM STANDARD POSITIONING SERVICE PERFORMANCE STANDARD"

http://www.gps.gov/technical/ps/2008-SPS-performance-standard.pdf

General GPS accuracy information: http://www.gps.gov/systems/gps/performance/accuracy/

I've read with some consumer/civilian gps units are able to achieve around ~2 meter accuracy without some form of correction technology.