3.4 RC1 Enhanced Camera Trigger

First of all, the current code rocks!! As it has for quite a few releases now!!

I’m in the process of testing out the enhanced camera trigger with RTK GPS. To check the viability of not using Ground Control. I have a highly accurate test location setup with around 20 control points set with mm accurate survey equipment.
I am using the standard 3DR GPS for Navigation and a Piksi as GPS2 for logging and processing after the flight (mainly because the Piksi RTK is too flaky for flight navigation). I’m currently flying with a Sony A7 using the Tuff Wing Hot Shoe cable. Everything works great!!
My only issue is how do I geotag the images with the precise x,y,z position of GPS2?
The CAM messages that are created correspond to GPS1 and the sampling rate of my GPS2 isn’t fast enough to log at the speed I’m flying (~7m/s), unless I interpolate manually. I get a GPS2 position about every tenth of a second. Can I get the CAM message to use GPS2 instead of GPS1? Or is there a better way to do what I’m trying?
I have a Reach GPS on the way as well so I can test the two against each other. I know they have a Hot Shoe setup that will tag the RINEX file when the camera fires as well. I’m planning to use that for post-processing.


Hi, Steve! Do you have any progress with using GPS2 instead GPS1 ?

@aerocub Yes, it worked great with GPS2. The best way I found was to just extract the data from the log file. However, I am no longer running in RTK because it’s not needed. I now just have an Emlid Reach along for the ride and post-process the GPS. I’m using the Hot Shoe to tag as well.


I have a question regarding enhanced camera trigger.
Pixhawk logs the exact time of camera trigger in UTC? how
accurate (not precise) is that timestamp?
If I process data from second GPS that is not connected
to Pixhawk and get precise position and time, can I directly
relate this TRIG messages with precise position? I know I
have only 10 hz position data, so interpolation has to be done
what I want to know is, if the these two information
(camera precise timestamp and precise position)
are related to the same time frame or can there be a delay?

Check out the “Enhanced camera trigger logging” section of the arducopter documentation:

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I looked at it, but there is no information about
what is the source of time for Pixhawk.
Obviously it is GPS (what else could it be),
but how accurate is it? What I am wondering is,
does Pixhawk clock accuracy match the precision
of hotshoe signal logging.
Pixhawk is using data stream from GPS for time synchronisation
with it’s internal clock, but that data stream can be delayed as far as
I know and is not accurate. For accurate timing information it should also
use PPS info from GPS unit (does it?)
So here I see the problem, I have precisely logged time on Pixhawk, but
I don’t know if it is also accurate so I would confidently use that
time logs with post processed GPS positions from separate (better and not attached to pixhawk) GPS unit.

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I think I understand what you’re asking now.
Yes, I believe the GPS Time field in the Pixhawk Log is directly from the GPS unit, so 1 PPS.
The exact time of when it was sampled has a slight delay from when the hot shoe sent the signal to the Pixhawk and the shutter closing. I believe I read somewhere it is around 20 ms?

Hello again,
today I tried this new feature on pixhawk and I have some questions:

First, I get cam and trig messages if I set
It does not seem to affect anything.

Second, the TimeUS parameter is accurate to microsecond, while
GPSTime is changed only if the time delay between TRIG and CAM is
more than 0.2 s, so basically 200 ms resolution. Isn’t that still a little low?
Flying at 20 m/s that is 4 m resolution

Any discoveries to report regarding the enhanced camera trigger logging accuracies? I’ve seen anything reported other than this thread.