Seems to be a lot of discussion re. CORS (Continuously Operating Reference Stations) & cell phones for differential. So, I went to the maps someone referenced in the threads below. Looks like US Govt provided towers vary a lot. From what I see, most ag states don't have a lot of them & they seem to be concentrated more towards high population areas. Not conducive to ag work, I'd say. Am I looking at the maps wrong? You can click on any given state map using the linked map:

http://www.ngs.noaa.gov/CORS/

Looks like IA has about 4-5 of them? MN has 2-3? SD has none? But then OH has about 500 of them! How did that happen? Also-I assume if they say co-op, they belong to someone & you're probably SOL anyway. Looks like closest to me would be about 35 sm (that's how we measure longer distances here)....though it's hard to tell specifically where tower is.

So, here's questions:

Sampling frequency-appears to be 1-30 seconds. How much is necessary? Seems to be mostly 5 second kinds. A few 1 second, a few 30 second.

Why does OH have 500 of them & WI only has 3-4?

Do you get a separate cell phone service for that gps differential if you're going to use cell/Cors thing? Doesn't the bill get big being locked on 16-18 hrs/day "in-season"?

So, how far from the CORS station can your cell phone be? Does that distance make a difference?

Since they're govt operated, are they subject to periodic "shutdown" for whatever reason?

I absolutely hate the "delay" in cell phone communications. Does that not play into navigation?

How strong does the cell phone signal need to be for usage? Does that signal strength affect accuracy? We have some farms w/OK signal, some w/questionable...occasional "drops". Carrier company doesn't seem to make a difference. Most that travel for a living around here carry 2-3 cell phones (different carriers).

So-why is a CORS better than RTK?

Thanks.