static Base/moving Rover options in RTKPOST

[filipnil]

I'm currently working on a school project where we have a static base (F9P) and a moving rover (F9P). Both have multi-band GNSS Antennas.

We collect data on ubx format and through RTKconv we convert from ubx to .obs/.nav files for both the base and the rover.

After our preprocessing we want to get fix or float status in the .pos file, right now we only getting Q=5=single. We are doing something wrong. What options should we use in RTKconv and in RTKpost to get fix or float status with our setup static base and moving rover ? Any tips? Or other threads we can read more about a similar setup?

To extract the ubx file we are using two arduinos, one connected to the base, one connected to the rover. Have anyone done similar and have some code for this to share?

Thanks in advance /Filip

[geofis]

Hello Filip.

I suggest you check some options I can think of that are usually related to the described behavior. Press the "Options" button in the RTKpost app, and check the following:

• In the "Setting1" tab, check that you have the "Positioning Mode" set to "Static". Also, in this tab, check that the needed GNSS constellations are enabled.
• In the "Positions" tab, section "Base Station", select a meaningful option from the drop down list. If you know the position of your base station, select Lat/Lon/Height and type it in the boxes below, or just select "Rinex Header Position" instead if you want to use the average position stored in the header of the base station rinex file.

Also do a sanity check of your .obs files using RTKplot or by browsing through the RINEX file (v 3 is a easire to read than previous versions). You may see epochs consistently stored (e.g. without gaps) throughout the file.

[filipnil]

Hi thanks for your answer, is the mode still static although the rover is moving while the base is static?

"Without gaps" can you specify this more? I'm really new to RINEX. Or is it like if I drag the rinex file to RTKplot i will see if the curve is continuous or not? How big of a gap is okay and is it okay if it is some gaps or should it be no gaps?

[geofis]

Oops, sorry, I forgot the part where you mentioned the moving rover. Therefore, the "Positioning Mode" should be set to "Kinematic".

Regarding the "gaps", I mean you may look at your observation data to check for consistency using RTKplot. First, use RTKconv to generate a RINEX file of observations (obs extension), then drag it to RTKplot and select the "Sat Vis" mode. The plot should show a dot for every epoch collected (this is related to the RATE option in the receiver configuration).

For example, this plot was generated by a faulty receiver:

And this one was generated by a flawless receiver:

[filipnil]

@geofis Would you say that this is a faulty receiver? The left picture represents the base and the right the rover. What rate should we use to collet data?

[geofis]

@filipnil

It is difficult to say whether the receiver used as the rover is faulty or not, but the gaps after 12:30 are not supposed to occur. In some cases, this behavior is related to a power source with low voltage. Does your ZED receive power from a USB port?

However, even with the gaps showed, the rover should have a fix during the time intervals in which the signal is continuous (e.g. 12:20 - 12:30).

I use 1 Hz in both base and rover without issues.

[filipnil]

@geofis Okay, our setup is on a breadboard and driven by a battery -> so probably there might be som loose cables that causes us to lose power :)

We got the ratio 15%/85% fix/float in our post-processed solution. If you have time, feel free to give it a try to post-process our data. And see what ratio you get.

Here is our data: base_rover_data_UBX.zip

[geofis]

@filipnil

I guess the low fix rate may be related to voltage drops. I was having a similar issue weeks ago; as my setup includes a Raspberry, and I feed the receiver via USB, I was having problems with voltage drops. I changed the cables (the shorter the better) and used a better power supply, and the issue went away completely.

You could try using a higher amperage adapter. You could also use a multimeter to see if the voltage remains stable enough after the receiver is connected and fully operational.

I looked at your data, performed a PPK solution and got the same fix rate as you did.

[filipnil]

@geofis Hi again.

Our receivers works now. Now we want to just log single rover points. So we have a program that only extract single raw messages from our rover when we press a button. The base is logging continuous. The rover sat view is below. Is it possible to get a reasonable result with this method? Do you know? Our do you have any tip on how we can do instead?

[geofis]

@filipnil

Sorry for my late reply.

What you are asking for is PPK (post processing kinematics). Since you have to raw files, one from the rover and another from the base, you can do this. The workflow is typically as follows:

• First, extract the observations from both files in rinex format using convbin (CLI) or RTKCONV (GUI). From the base raw observations, also obtain the navigation data (only one set of navigation files is needed).

• Second, use rnx2rtkp (CLI) or RTKPOST (GUI) and specify the location of observation files for the rover and the base, as well as the navigation data files. In addition, you will need to specify some configuration options. I suggest you to follow the recommendations from this blog post.

Finally, I am not sure if your file has some issues, but the screenshot seems to show large data gaps.

[bigman996]

yes