PPK for gis mapping?


I am setting up the system for GIS mapping with a single rover and CORS correction. Obviously, I will be mapping in places where none or bad data signal is available. In such cases storing positions in SD for later RTKLIB processing is desirable (PPK). I have never worked using PPK and RTKLIB so I will have to investigate. Nevertheless, my main question is:

SD is storing ALL positioning information for ALL the time the alpha is switched on. But I only need data for those points I am storing on my Android GIS app. How do I correct just those points using PPK? Do I need to double look for GPS lectures in app and SD, correct and make a correlation and discard ‘unsurveyed’ points?

Thanks in advance

Please see section 3 Table 3-1 description item #6 on start/stop control of SD Card logging. One can log a file for each survey location if needed.

If the SD card logging is not turned off between the survey locations and assume everything is stored into a single file, if the receiver is kept stationary for several minutes at the survey locations, then when doing RTKLIB post-processing one should find clusters of points at the survey locations and be able determine center of the cluster. I’m not familiar with RTKLIB, maybe other users familiar with RTKLIB post-processing can offer suggestions.

Here good reference for PPK and RTKLIB.


I think the Pin 3 in the 4-Pin Connector is a bit confusing. Is it for trigger the camera or the timestamp for the PPK? It is IN (going the input to RTK GNSS Receiver). How can it trigger the camera when it is receiver an input from the camera?

If the pin 3 is really for triggering the camera, where we get the time mark / time stamp which I think needed for PPK?


Pin 3 is for connecting with camera hot shoe to record the timing of taking picture. Yes, it is IN.

OK. Now, it is clear that Pin 3 is for “CAM Messages” or flash / shutter feedback.

I think you have to rename “External camera trigger input signal” to “Camera Flash / shutter Time mark / Timestamp input signal” or something that.

The “camera trigger” is really misleading since it does not trigger the camera, I suppose.


I could not understand why Polar Support is not answering questions in your blogs.

RTKLIB Post-Processing With Alpha


That is a good point. We will consider it. Thank you.

The informing system of the blog does not work very well. Thank you for reminding us.

Please check this topic out. Perhaps it helps your work with Alpha and VRS/CORS.

Jim Lin
Polaris GNSS Team

I don’t know why Pin 3 is no longer use to trigger the record the timing of taking picture in Alpha+

This is no good now. Alpha+ for Phantom 4 PPK.


Will have update firmware supporting this next week.

Hi, the update firmware to use Pin 3 (external camera trigger input signal), when can be released, I want to buy a module, Thank you for time

It’s already been released for a while. If you have Alpha+, simply update firmware via RTK Viewer.

Ooops, it appears the released Alpha+ firmware update was unable to support pin-3 external trigger time stamping due to I/O pin conflict between data logging and time stamp function. Still need more time to resolve the issue.

When completed, it would be possible to do raw measurement logging with time-stamp, and the converted RINEX log file will have event mark.

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Hi Jackson,

I hope it will be working soon, so Alpha+ can be useful for UAV Aerial Topo Mapping with PPK.


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New Alpha+ firmware supporting pin-3 (on the 4-pin connector) for external triggered time-stamp PSTI,005 in NMEA output has been released.

SD-Card recorded binary raw measurement will also have time stamp information. When using below program to convert to RINEX, event mark will also be generated.


The SD Card logging function could only support up to 5Hz logging with quad-GNSS. Will need to reduce satellite constellation if wanting to use higher update rate.