I use Trimble R8-2's with a TDL450H. They were all set by the dealer to CMR+ and I have left them this way but I think everything is capable of using CMRx. I was reading somewhere that CMRx uses better compression and thus less data has to be transmitted and your radio runs cooler and battery life is nearly doubled.
Any reason not to switch over to the CMR-x?
*** moved to Land Surveying ***
CMRx is a proprietary Trimble signal. If you have all Trimble eqiupment and won't be mixing/matching that is what I would use. Not sure about anything running cooler, but I could see it maybe helping a tiny tiny amount with latency because less/more compact data means less processing time.
CMR couldn't handle increasing data from more satellites, so CMR+ was developed to send data from base to rover in a compressed format. Now with even more satellites up the info has increased and narrow-banding has decreased the info path available so CMRx was developed, as I remember it's a zipped file version of CMR+. So yes use it, should help your performance in the field.
Protocol Position Accuracy
Position accuracies depend in part on the selected output format. This list is the greatest accuracy of the particular format output specification, NOT the WVRTN output. Depending on the chosen format (RTCM or CMR) and on the messages activated, the reference-station position information is rounded to different accuracies due to different definitions in the RTCM version standards.
The following rules apply:
When output is RTCM 2.1, position accuracy is 1 cm.
When output is RTCM 2.3 and messages #22 and #24 are disabled, position accuracy is 1 cm.
When output is RTCM 2.3, message #22 is enabled and message #24 is disabled, position accuracy is 1/256 cm.
When output is RTCM 2.3 and message #24 is enabled, position accuracy is 0.1 mm.
When output is RTCM 3.1, position accuracy is 0.1 mm.
When output is CMR, CMR+, or CMRx, position accuracy is 1 mm.
The above is a copy/paste from: www.cors.us (WV RTN)
Finally remembered where I read it. This shows another slight difference in the messages, and explained why I was seeing between 0.01' and 0.004' error between the data sheet and the coordinates seeded by the data collector upon dial-up.
NOT that I was thinking it made any real difference at all on my work/processing. The introduced error was well under performance expectations for RTK (will creep up horizontal on static, though). My underlying reason for wanting to know the source of the difference was so that I could be comfortable knowing that no unforeseen cause would arbitrarily also shift RTN work by a meter... Also I guess I'm just curious by nature.
Edit: This is a separate issue from what you were wondering about, just further highlights the differences.
Well I switched everything over today to the CMRx and it all communicated like normal. Time will tell if battery life is improved. I found the paper from Frontier precision and they state that the CMRx uses 40% less bandwidth than CMR+ and will nearly double your battery life. Hopefully it does as the base really sucks down the battery when set at 35watts.
And YES, the radio will run much cooler...
Drilldo, post: 276468, member: 8604 wrote: Well I switched everything over today to the CMRx and it all communicated like normal. Time will tell if battery life is improved. I found the paper from Frontier precision and they state that the CMRx uses 40% less bandwidth than CMR+ and will nearly double your battery life. Hopefully it does as the base really sucks down the battery when set at 35watts.
So have you seen any differences in performance? Mine came with cmr+ from the delaer as well, and i'm considering changing it to CMRx
MightyMoe, post: 276311, member: 700 wrote: CMR+ was developed to send data from base to rover in a compressed format.
CMR+ was developed to even out the flow of data and eliminate an every 15 second "burst" of station data, not to reduce the actual amount of data. CMR+ is basically the same as CMR with some minor differences. CMR sends the station data as a single message every 15 seconds. CMR+ spreads the station data out into little incomplete chunks which it sends every second. Every 15 seconds the rover then reassembles those little incomplete chunks into a complete full message and processes it. The actual observation data in both CMR and CMR+ remains mostly the same. With CMR+ the data flow is more even, but because of the extra message header and trailer overhead (more than twice as much overhead), the actual amount of data is increased substantially, not decreased. But it's an even flow of data and not bursty.
CMRx is a far, far more sophisticated protocol. It's not even comparable.
The best choice these days is CMRx if both base and rover have it otherwise RTCM3.
When output is RTCM 2.3, message #22 is enabled and message #24 is disabled, position accuracy is 1/256 cm.
Are you certain that's 1/256 cm rather than 1/256 L1 cycle?
My equipment supports it. Do i enable it on the controller on both sides under uhf settings, or do i have to connect with null modem cable and enable it internally on the equipment?