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Australia | Accuracy varies depending on the mix of GPS technology, plus terrain compensation (TC) with the steering technology, here is a VERY generic guide:
Best = L1/L2 RTK (fixed pos'n) GPS + 3D TC + Proportional valve Hydraulic Steering (+/- inches absolute accuracy)
next = L1/L2 RTK (fixed pos'n) GPS + 2D TC + Steering column motor (+/- several inches absolute accuracy)
next = L1 RTK (fixed pos'n) GPS + 2D TC + on/off valve hydraulic steering (+/- inches but very prone to dropouts and solar disturbances, short range)
next = L1/L2 SBAS (Floating pos'n) GPS + 2D TC + on/off valve Hydraulic Steering (+/- 4 to 6 inches absolute after 1 hr of operation)
next = L1 SBAS (Floating pos'n) GPS + 2D TC + Steering column motor ( +/- 8 to 12 inches pass-to-pass accuracy, +/- 30 inches absolute)
Worst = L1 standalone (Floating pos) GPS + no TC + Steering column motor (+/-40 inches + and basically unusable)
In short, L1/L2 GPS is more accurate than L1 GPS; Fixed position is more accurate than floating position; 3D TC is more accurate than 2D TC; proportional hydraulic valves are more accurate/responsive than on/off valves; hydraulic steering is more accurate/responsive than steering motors; absolute and pass-to-pass performance cannot be compared adequately.
Various manufacturers have steps in between these with different mixes of the key components. You have to determine what your farming operation requires, and how much you can afford to ensure you get a return on the investment. If you grow a row-crop of any sort then I have to recommend RTK (some will disagree). Terrain compensation is a must in my view. Proportional Hydraulic steering is nice to have but the on/off valves and motor solutions are good enough for many people.
You generally need to buy a base station for RTK, or if you don't want a base look for an RTK network in your area. There are fee-based private networks run by dealers, and Gov't run free networks such as those run by state DOT's. You don't need a base station for SBAS systems but there will be a fee each year if want more than WAAS or SF1 accuracy.
L1/L2 is the number of satellite frequencies used and is also called dual-freqency GPS; L1 is sometimes called single-frequency GPS. SBAS stands for Spaced Based Augmentation System and includes services like WAAS, Starfire 1 & 2, Omnistar VBS/XP/HP. They transmit extra data to the GPS receiver from space to help with accuracy.
Accuracy is also affected by how well you set-up your equipment, and in many cases, this is the biggest problem in getting the most out of your GPS system.
You have all of the options above and you can keep the old brown box if you like!
Do the research and you will be fine. Make sure you get the dealers to spell out the pro's and cons for each product. AgTalk has some great contributors so ask away. | |
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Which way to go.
