We seem to have connectivity issues on our statewide RTN. The base stations appear to be collecting data and the network server seems to be sending out the corrections. We get a lot of callers asking if the network is down. They tend to go from a fixed solution to float frequently. We cannot tell if this is a location issue, but it seems to be random.
Assuming the issue is with the cellular connections, what are some remedies we can look for to assist our users to stay connected? How exactly is the data used/transmitted on a cellular connection?
Thanks.
Bad/slow comms are the biggest issues that we see with our RTN here in Texas and Oklahoma.?ÿ Just like with RTK, if the correction is more than two seconds old, it is considered invalid and the residuals will jump up.?ÿ If the situation is not resolved, you will lose initialization.?ÿ The data is used almost the same as using a radio with a base/rover setup with one caveat.?ÿ At least with the Trimble Pivot software, the data package is bi-directional.?ÿ The rover sends it's location to the server.?ÿ The server then creates a Virtual Reference Station (VRS) at or near the point of initialization to keep the baselines short and then keeps sending said correction until the user get a specified distance from the VRS or the survey is ended.
The biggest thing that I tell our customers is to make sure they use the fastest APN available, i.e AT&T's "Broadband" APN.?ÿ The second thing I check is where is there sim card.?ÿ If it is in an older device with a 3G modem, they will likely experience more downtime.?ÿ I don't know about all of the providers, but Sprint and AT&T are getting ready to sunset their 3G networks.?ÿ I have been advising our users to start moving towards using 4G hotspots.
What part of the world are you in, Dan??ÿ What manufacturer is the majority of your user base?
Kris
Thanks Kris. I am located in Iowa. Most users use US cellular or Verizon or their cellular connection. LTE is available in many areas, but due to hills and distance from larger communities, user can find themselves in 3G.
I have use VRS while using Trimble in the past, but most users use RCTM 2 or 3 with iMAX or MAX mount points. MSM iMAX is provided as well.
The equipment at the base stations are Leica.
I have been suggesting users use the MSM iMAX mount point because (from what I gather) it is the latest and greatest method of transferring data and is the only mount point to provide Galileo corrections. I’m not sure why vendors are telling users to use RTCM.
I can't speak to the MSM iMAX solution, but RTCM is vendor agnostic and anyone regardless of equipment make can use it.?ÿ As long as the firmware in the receiver/data collection package is up to date enough to decode the RTCM version being transmitted.
I recently switched from CMRx (which was problematic because one of our R8's could use it and the other could not) to RTCM3.x. Also, we could not get CMRx to work using a Trimmark 3, no idea what was happening but since the RTCM worked, I just gave up and switched. It was strange, the CMRx would work over cell, but then not work over radio, and this only happened with certain receivers. That is the drawback to having a mixture of receivers (2 4700's, 2 5700's, R7, 2 R8's, 2 R10's). I have also had issues from some VRS's using CMRx even though there is a mount point for it.?ÿ
Thanks for your feedback on this, Gavin.?ÿ?ÿ
The radio issue is limited to the TM3 only, which is puzzling since my understanding (which may not be entirely correct) of this is that the actual format (CMRx versus RTCM) should be transparent to the radio. The radio link format (Trimtalk V1 9600 I think, don't have it here in front of me) is what should matter. The receiver decodes the reference ID but times out in "waiting for information from the base". But it works fine for RTCM or CMRp over that radio. Strange. It may be a problem unique to this radio, which was given to me. We had to narrowband it, which we did. And I have only used it a couple of times, it is rare when we need a radio link (normally use cell, I have both internal (R10) and external cell modems). But we were in an area recently with bad cell coverage doing hydro, wound up using GPS only due to the CMRp protocol being on one unit and CMRx on the other. But it worked fine, hydro is very tolerant of low number of SV's because the lake level was stable, so we only really needed horizontal to a few decimeters.?ÿ
I have an RTK bridge that is going to be obsolete after the end of the year (3G), so we have pretty much stopped using that. But is always worked fine with CMRx. That was before I got the cell modems.?ÿ
I believe that the 9600 bps option for TM3s was removed at narrowbanding. I have had the same experience.
