Below is straight off the Iowa RTN website http://www.iowadot.gov/rtn/

It looks to me like there are some issues yet to be worked out, which relates exactly to what I have been seeing all spring running this network.
(see previous post – http://htsag.blogspot.com/2009/06/finally-finished.html )

IaRTN users have reported having problems with initialization, frequent base changes and shot repeatability the last couple of weeks. We are and have been working with the end-users reporting this issue and Leica Geosystems to determine the cause and resolution of this issue. We suggest you evaluate the impact this issue may cause your surveying operations.
When using the IaRTN, please use the nearest option which will direct your equipment to the nearest base station minimizing errors due to baseline distance. A list of the Nearest data products on the IaRTN are listed below for you selection.
NTRIP Port 10000

RTCM3_NEAR (GPS+Glonass Solution)

RTCM2_NEAR – (GPS Solution)

CMR_NEAR – (GPS Solution)

CMRP_NEAR – (GPS Solution)
TCP/IP, GPUID Ports

RTCM 2.3 (GPS) 11002

CMR (GPS) 11003

CMRP (GPS) 11004

As a sound survey practice, make sure you check the repeatability of your shots as well. Another suggestion, if you may deem it appropriate, is to use your conventional GPS base until we get this issue resolved.
We apologize for any inconvenience this may cause, and we will keep you updated on the progress of the resolution of this issue.