Hi.

I am a GNSS engineer who works on the receiver on your tractor.

We both specify and test (obsessively...) TerraStar for 1 inch accuracy (https://tinyurl.com/n4yduya4). Unless you have a lot of tree lines or other signal problems you absolutely should get inch pass-to-pass accuracy. Year-to-year repeatability, however, depends on if the AgLeader uses the receiver feature that corrects for continental drift (sorry, I don't actually know). If they don't, then because Iowa is moving about 3/4" per year that means this much error accumulates per year. If they do use the feature, then you would have inch year-to-year repeatability.

If I had to guess (?) I'd say AgLeader does use the receiver continental drift feature; it was created specifically for Ag applications.

20-25 miles is a reasonably long RTK baseline, although if the Iowa CORS is doing "network RTK" (averaging information from multiple stations) then the effective baseline will be shorter. A problem with RTK is that it is more dependent on ionosphere activity. If the ionosphere is quiet, then RTK will probably perform better than TerraStar: most notably, it will get to 1 inch accuracy faster. If the ionosphere is active, then (at some point) I would expect RTK to become less reliable than TerraStar. This is because the TerraStar solution makes no assumptions about the ionosphere but the RTK solution does. When these assumptions break down, solution reliability is affected.

Also, as has been noted elsewhere, if you have problems with cellular connectivity in your working area this will obviously corrupt RTK.

Thanks.