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| Sounds like you might be fighting WAAS issues, with the recent changes to the WAAS system the Ag community has had a difficult spring. Couple of hints:
1: Lowering the Elevation mask will not effect WAAS tracking, the mask only affects the GPS satellite tracking , and the mask is already pretty liberal at 8 degrees. Lowering this mask will allow the receiver to track low elevation satellites which are more prone to error.
2: The SNR mask filters the GPS satellite selection by signal strength, raising it will make the receiver more selective in that it requires higher quality signals, lowering it allows the receiver to use weaker and potentially noisy signals. The SNR mask has no effect on WAAS tracking.
3: The differential correction age limit is by default 240 seconds for WAAS and should not be raised any higher because corrections older than 240 seconds are too old to be accurate, lowering the age will make the receiver more selective. Recommend the default here.
4: The OnPath filter is very important if you are having problems tracking WAAS. The OnPath filter works by exponentially decaying (very slowly adding) position shifts into the guidance rather than adding them in real time. For example with a Decay Time of 1 minute if the user is running along a swath and they drop from 8 satellites to 7, without OnPath it would have shifted 5" to the right instantly, with OnPath the filter detects the change and builds interpolated guidance to continue straight, during the first minute the filter slowly adds half (2.5") the shift to the current guidance, then after two minutes it adds half of the remaining shift (~1.25) and this goes on until the user is at the current GPS position. The decay time is adjustable from 1 - 999 minutes, for fields with treelines, buildings or terrain obstacles it is recommended to run the filter from 30- 120 minutes. For more open field conditions the filter can be set higher all the way up to 999.
5: In some parts of the country users can track both WAAS satellites which can lead to problems if the receiver switches between the satellites on subsequent passes. For most users in the western states the AOR-W satellite is the better choice, so disabling the POR satellite will restrict the receiver from tracking anything but AOR-W.
Hope that helps, Good Luck | |
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On Ground Pass to Pass Errors with EZ-Steer WAAS
