Get triggered positions from SD-card log files of Alpha

Here I would like to show the processes of getting the trigger positions from SD-card log files of base and rover.
Roughly speaking, the log file in Alpha’s SD card contains

  1. [both base and rover sides] GNSS raw measurement data.
  2. [rover side] GNSS raw measurement data at regular sampling points at 1/5/10 Hz.
  3. [rover side] GNSS raw measurement data at trigger points (trigger input comes from pin 3 of the 4-pin connector on Alpha).

The processes to retrieve trigger positions will be

  1. From base Alpha, we get logged base RTK correction raw data file, say, “b.DAT”
  2. From rover Alpha, we get logged rover positioning raw data file, say, “r.DAT” (with time stamps of regular sampling points and user trigger points)
  3. Feed files “b.DAT” and “r.DAT” into RTKLib utility tools do PPK processing, and we can get the recorded path file “*.pos” with timestamps and positions.
  4. Use the RTKViewer’s new feature “SD Timestamp Acquisition” (will be provided later in version update) to extract timestamps of trigger points from “r.DAT” file (mentioned in point 2). The triggered timing will be stored in the output file named “r.DAT.txt”
  5. Use PC utility locator.exe to find positions of trigger points by providing path file “*.pos” (mentioned in point 3) and triggered timing file “r.DAT.txt”, you can specify the output filename like “out.txt”

PPK results and trigger points at turning points and middle way are shown here.

PC utility locator.exe and sample files are zipped in the rar file.

Hi Jim,

I think you should place the category in PPK, not others so people can see.

You posted it 16 days ago and I only see it today.

Hopefully, somebody who owns UAV with camera triggering flight controller (e.g. Pixhawk) and Alpha can verify this process for UAV Mapping with PPK.


Hi Jym!!
When trying to use the locator.exe file I noticed two things: that the negative sign (coordinates in decimal degrees) makes it read only longitude and altitude instead of latitude and longitude (due to the negative sign of both being in America South) should be because the file counts the number of spaces or tabs. Another thing is that even finding the longitude, the values ​​of this longitude do not match the data of the .pos file. Following is an image for verification. Maybe the signal (and consequent error in obtaining the data) imputes some error, I imagine. Shouldn’t locator.exe take the entire line corresponding to timestamp in the .pos file?what was expendable could be discarded by the user
Best regards.

I used a distant COORS base for verification and found that the locator.exe file is taking the coordinate value from the base and making some calculations, it is clear from the fact that the altitude appears
665.95 which is the altitude of the base. But even if it were correct, it would be better if the tool this tool locator.exe was already inside tools in RTKViewer, such as timestamp. Are there any predictions for this to happen?

I’m leaving a link with data where the coordinates have negative sign, I believe this is the problem, you knew how to say.


Please allow us some time to answer you.

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Hello Jim!! Any developments?

nothing yet? what’s the problem?

Hi Rods,
The file format of your pos file (Rover_SDL_004.pos) is not the same as the one of the pos file I obtained (SDL_003.pos in the zipped file locator.rar). Your file is of the format with lat/lon/alt values

while mine is of the format with differences of lat/lon/alt in meters

Please go either of the 2 ways

  1. do PPK using the same RTKLib package (Attention: Use the tested RTKLIB to do PPK) with the same operations (https://www.youtube.com/watch?v=TcUxvhxBXWc) to get pos file with the same format with mine.
  2. write a simple tool by your own to get the coordinates of your triggered points. (should be easy, you just get the coordinates with the triggered time stamp; you do not need to calculate)

Hi Rods,
Just built a tool for your pos file. Please try it.


Thank you Jim!! That’s great. A question: Do you intend to put these apps on RTKViewer in the next updates?

Hi Rods,
This is not scheduled in RTK Viewer’s plan yet. Please use the utility tool for now.
Sorry for the inconvenience.


Jim, Hello, I am thinking of creating a GUI front end for the console applications rtkconv, rtkpost, “locator.exe”, “getriggeredpoint” to create a flow that can semi-automate the PPK process. For this, would also be necessary the "timeout of SD acquisition " separate from RTKviewer to complete the sequence. Would it be possible to release the separate RTKviwer application as an executable? Or, if possible, if it’s not asking too much, the source code of these applications so that I can (not just me, but whoever wants to) develop an application to sequence the data flow to obtain the PPK semi-automatically? in GITHub repository for example, so that can we work together?.this already exists for another low cost gnss, so it would be something to equate the use but with the Alphas.Am I dreaming big?

Hi Rods,
The integration of tools involved in PPK processes has been in my mind for a while.
The “SD Timestamp Acquisition” function of RTK Viewer can be extracted out and can be built as a command-line application, according to the response from one of my colleagues. However, it will not be in his high priority list. I will let you know the status.
Making RTK Viewer open source seems not likely to happen in the near future.
Thank you for the great idea.

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Hello Jim !!
I thank you for your attention. I imagine the difficulties involved in these processes. I also have some tasks that make it impossible for me to go deeper into the subject but I already have an outline of what I imagine to be a sequential data entry application for the PPK, but at the moment just the design, a challenge is the geotagging of the photos (without this I don’t think it would be worth building the app).
I believe, although the new Alpha L1 / L2 is another firm step for RTK, that PPK is still a tool that can help integration with other legacy devices and be quite useful when it is difficult to obtain data via RTK. I’m available to help. greetings