Float RTK mode to fixed RTK using LC29HBS and LC29HDA

I have configured both the LC29H BS module as a base station and the LC29H DA module as a rover device to establish RTK communication. The base station is working with SNIP, and when I connect the rover to receive the data, I noticed that it remains in Float RTK mode and does not switch to Fixed RTK mode. I should mention that the position applied to the base station is not accurate because I haven’t been able to achieve a better value during the survey-in process. I’ve monitored the connection for a considerable amount of time to see if it changes mode, but nothing has happened. What could be the problem? I’ve reviewed the documentation but haven’t found anything that triggers the mode change. Best regards.
These are the commands I have used for both the LC29H BS and LC29H DA:
LC29HBS:
*$PQTMRESTOREPAR 13
$PQTMCFGSVIN,W,1,xxxx,15,0,0,0*26
$PQTMCFGSVIN ,R*26
$PQTMSAVEPAR*5A
$PAIR434,1*24
$PAIR432,0*23
$PAIR432,1*22
$PQTMVERNO,LC29HBSNR11A01S,2023/02/13,10:14:06*27

LC29HDA:
$PQTMRESTOREPAR*13
$PQTMCFGRCVRMODE,W,1*2A
$PQTMSAVEPAR*5A
$PAIR062,2,0*3C
$PAIR062,3,0*3D
$PAIR062,5,0*3B
$PQTMCFGNMEADP,W,3,6,2,2,3,2*36
$PQTMVERNO,LC29HDANR11A03S_RSA,2024/03/19,13:55:31*20

Have you changed the convergence time of survey-in of LC29HBS?
The default convergence time of LC29HBS is 43200 times, so it is definitely impossible to output a fixed position in a short time.
You can verify it as follows.

  1. Send the command “$PQTMCFGSVIN,W,1,300,15,0,0,0*15” to configure the Survey-in mode. After positioning, when the 3D threshold is less than 15 and the cumulative count is 300 times, the Survey-in is completed.
  2. Send the command “$PQTMSAVEPAR*5A” to save the Survey-in configuration command.
  3. Send the command “$PQTMCFGMSGRATE,W,PQTMSVINSTATUS,1,1*58” //Open PQTMSVINSTATUS and check the convergence status of Survey-in.
    The command format is shown in the figure.
    When the <Obs> value is equal to <CfgDur>, it means that Survey-in is completed.
  4. When Survey-in is completed, you can send the command “$PQTMCFGMSGRATE,W,PQTMSVINSTATUS,0,1*59” to close PQTMSVINSTATUS message.

Hello George.gao, thank you for responding. Yes, I followed the steps you mentioned. In fact, I’ve tested it with different times: 1 hour, 2 hours, and 4 hours, and with a distance of 15m (at the moment, I have the command running on another LC29HBS with 28,800 seconds and 12m). It’s worth mentioning that when executing the survey-in command, I waited for the final result before testing the RTK connection between the devices. The results I got with those times showed that the 4-hour duration allowed the rovers to reach Float mode faster, but they still didn’t manage to enter the fixed mode. Now I will run the calculation again, but I will position the antenna in a different location. The antenna I’ve been working with is outdoors. My goal is to work with centimeter-level GPS, so I need to achieve precise results. Thank you very much

Hi @Jorge_Pardo

  1. Only after the Survey-in of LC29HBS is completed, LC29HDA can use the data of LC29HBS.
  2. LC29HDA achieves centimeter-level positioning. The antennas of LC29HBS and LC29HDA need to be in an outdoor OPEN environment.
  3. In order to further improve the accuracy of LC29HDA, you can send the following two commands to LC29HBS. (These two commands cannot be sent to LC29HDA)
  4. $PAIR432,1*22 //LC29HBS outputs MSM7
  5. $PAIR513*3D //Keep configuration

I solved it; apparently, even when outdoors, the position of the antennas wasn’t very good. I changed the position of the base station antenna and obtained a certain value by running the survey-in mode for an hour. I should also mention that I managed to establish a connection between both devices using a TCP server and TCP client, in conjunction with RTKLib (both modules are connected to respective Raspberry Pi Zero 2 units).

My problem now is as follows: I managed to establish RTK Fixed mode, but when I move the rover, it loses this mode and switches to RTK Float. It doesn’t return to Fixed mode until it remains in a stationary position for several minutes and close to the internet it is connected to. I monitored the terminal of the Raspberry Pi to which both modules are connected and observed that the connection between them sends data and stays connected; I did not see any moment when they lost their connection.

Could this problem be due to the quality of the internet signal, the quality of the antenna, or the position set on the base module, considering it was given an hour and a 3D_AccLimit of 15 m? Thanks a lot

Hi @Jorge_Pardo

  1. LC29HBS and LC29HDA must use dual-band antennas (L1+L5). Please provide your antenna signal and we will confirm it.
  2. When the LC29HDA module is moved, make sure that the differential data of the base station can be obtained all the time, and confirm that more satellites can be searched in the test environment and there is no interference in the environment.

Hi @george.gao. For the LC29HBS model, I am using this module and antenna: (https://es.aliexpress.com/item/1005007606687669.html). For the LC29HDA model, I have the following: (aliexpress … /1005006605427126.html). How can I get more information regarding the relevant data? I am currently conducting more tests to observe the performance of Fixed RTK.

Hi @Jorge_Pardo
Please provide your email address and I will send you the relevant information via email.

Hi! I have the same setup as Jorge_Pardo (the same antenna for rover and base station), LC29H easily goes in to Fixed RTK when the rover is stationary but when I move the rover it switches to the Float RTK mode. After some time (few minutes) rover returns to the Fixed RTK mode. Could you help somehow?