2 or 5 Hz Base Transmission

[Jim Campi]

Gentlemen,

I noticed several days ago that a 2 hz base transmission rate was added as an option in the LS and described on the web.

Today I noticed that the web is describing the rate as 5 hz.

There must be something going on in the background as a transmission rate of 0.5 seconds equals 2 updates per second or 2 Hz.

Did I miss something or is there now an option to set the base trans at 0.2 seconds?

 

[Matt Johnson]

There will be an option to set the base transmission period to 0.2 seconds in the next release of J-Field. Be aware that increasing the transmission rate increases the battery usage of the radio and will also increase the heat generated inside it. For 2 Hz corrections you should use D8PSK or D16QAM modulation. D16QAM has the most bandwidth and is required for 5 Hz transmissions but may reduce the range of the radio some. If you are using the 35 watt radio you probably need to use than fan with 5 Hz corrections if the output power is more than 4 watts.

 

[Jim Campi]

Thanks for the update Matt.
I use the 1 watt radio.

 

[Jim Campi]

One more quick question.

Does the increased base rate impact precision or accuracy?

 

[Matt Johnson]

The biggest advantage it has is that it reduces the time required to obtain a fix and you should be able to go through the RTK Verify and Validate processes much faster. Multipath causes the position to drift over time regardless of the RTK rate so increasing the RTK rate will not improve this, only longer observations will.

 

[Jim Campi]

Outstanding.

is Javad going to 100 hz? Apparently that is an optional upgrade?

 

[Matt Johnson]

5 Hz is the most a UHF radio at 12.5 kHz channel spacing will support. Faster rates currently work over TCP connections if your connection has enough bandwidth.

 

[Javad]

The 100 Hz is very different. It uses the one second update rate and uses it for the next 100 epochs. Our new 5 Hz is "true" 5 Hz which base transmits corrections at 5 Hz. It is very different. Radio links cannot transmit corrections faster than 5 Hz. Enjoy!

 

[Jim Campi]

I tried the updated base transmission rate of 2 hz and was suprised at the following:

1. Time to a fixed position. I was surveying a fairly open rural property and notoced that the LS fixed at least 2 engines dramatically faster than 1 hz base transmission. In many cases the the fix occurred within a few seconds.

2. Total number of fixed engines. Prior to the updated base transmission rate, there were many, many instances where only 2-4 engines fixed. After updating, 6 engines were typical. If I'm doing a precise topo with 2 fixed engines it will take at least 100 epocs for an acceptable position. 6 engines only requires 10 epocs. This is a time savings of 90 seconds per point!

3. Fixed position under a canopy or near an obstruction. I was able to set up many times near or directly large shrubs that normally would have resulted in a floating position. Not only did the LS fix a position, it typically fixed within 15 seconds.

Prior to the update, there were typically locations that simply wouldn't fix. I ended up relocating the rover, abandoning the point or using an optical solution. After the update this happened 1 time and I was able to move the rover slightly and gather the data I needed.

I really appreciate the latest update. It's going to increase efficiency and open up sites that wern't appropriate for GNSS surveying.

 

[Matt Johnson]

I noticed yesterday that even at a 4 watt output power the radio will get very hot broadcasting at 5 Hz so I would recommend using the fan at a 4 watt output with 5 Hz corrections.

 

[Matthew D. Sibole]

Yes mine was super hot today using 0.2 sec transmit rate.

 

[Monte King]

When I was running the 5 hz(0.2 trans rate D16QAM mod type) the box in the action screen for fixed/float/standalone status was not keeping up with the fixed status in six pack screen ie the status box showed standalone even though all 6 fixed in 6 pack screen. I can collect a point with no issue as the software is using the actual fixed data shown in 6 pack screen but when staking out if the status box is showing standalone the bearing and distance to the staked point is based on a standalone solution. Also the VRMS box in collect or stake action screen is representing a standalone solution when the status box shows standalone. The fixed/float/standalone status box will show fixed at random intervals. I am using the version available under testing without the "code." Is this a known issue or maybe I am doing something wrong. BTW the 2 hz settings work very well, love the faster updates, even in extreme multipath its an animal!

 

[Matt Johnson]

Monte I have seen this issue a few times as well.

 

[Monte King]

I just watched Matt S video on surveyor connect running 5Hz and I noticed the epoch recording was way quicker than when I was trying 5 Hz. Mine seems to fix faster but it collects(clicks) at same rate as 1 Hz. Is there something I need to do on the T2 or maybe some other setting I am missing.

 

[Matt Johnson]

That is actually my video.

Check to see if the RTK rate is set to 0.2 Sec. in Setup>Advanced>RTK/DPGS>RTK Rate. If you used Base/Rover setup it should have been automatically set to this. Also check that you have the 10 Hz RTK and Recording options in the Options Update screen:

 

[Monte King]

Lol I actually meant to have Matt's on previous post but that still could have been either of you! I did check that it was .2 second rate, I will check the options but if I remember right they are the 10 of 100 as your screen shows.

 

[Matt Johnson]

Did you notice the TX light on your radio? It should pretty much be solid at 5 Hz rather than blinking once a second.

 

[Monte King]

Just checked and it has 10 of 100 options. Jfield v1.11.2.43. Even at the 2 Hz(.5 sec rate) it fixes noticeably quicker but records epochs at same rate as normal(prior) settings.

Just saw your post, no I did not look at the tx light, will have to check that tomorrow. Maybe I need to update radio firmware?

 

[Matt Johnson]

No radio firmware updates are required but you do need to have the 10 Hz RTK option on the base station receiver.

 

[Monte King]

Ok. Again I think I recall the T2 having 10Hz update option but I could be wrong, I will check it out tomorrow. If it does have faster update option I will set up and look at tx light on the radio and will let you know if I still have issues.