Dear Sahar,

There are several techniques for instrument synchronization, but there are many questions:

What is the main difficulty for thy synchronization? e.g. distance between the systems? drift of instrument clocks?

Do the systems "cooperate" each other? e.g. need for common shared clock signal? Or one triggers another one?

What synchronization accuracy do you want to achieve?

So please specify the problem a bit more in details.

Best wishes,

David

Dear Sahar,

we have developed an event-based procedure for temporal calibration between a TLS and several total stations (for kinematic laser scanning) and in a second try we reapplied the approach to synchronise a TLS and pair of cameras. If that is of interest for you please let me know.

All the best from Berlin

Daniel

Dear David,

Thank you very much for your response.

The main difficulty for the synchronization of our instruments is that each measuring system starts its measurement in its own scale. forexample one of the instruments start at 10:00 and the other at 10:02:35 UTC and also with various integration and averaging times through the measurements

and we have for instance measured values every 5-10 seconds for first instrument and every 13 sec for the second one.

Therefore when we would like to compare the measured values they are not surely presenting the same results or better to say we can not compare the results in exact snapshot of the measurements.

Synchronization in the accuracy of seconds sounds nice I think in our measurements.

I would appreciate your feedback.

Wishes,

Sahar

Dear Daniel,

Thanks for your explanation of your experience. What do you mean with the event-based procedure for the temporal calibration?

Looks very interesting to my mind. Although our measurement devices are different with yours but I think I will surely learn alot from your expereince.

Therefore, I would be grateful and surely interested to know more about your experience.

All the best from Hannover

Sahar

Dear Sahar,

Usually time synchronization can be perfomed based on: 1- Multiplexer, 2-using a real time unit/processor and 3-GPS event. However, there are differnet methods of schnchronization based on: 1-Clock-controlled registration, 2- Event-driven registration by triggering signal from the master sensor to the slave sensors and 3- Event-based registration using central time base e.g. PPS or DCF77. Subsequently, it is important to define an accuracy and accordingly choose a proper technique. In addition, if you just have the time series of the data in their own time reference, you can refer to the following mathwork page regarding comparing signals to find a cross-correlation between them.

https://de.mathworks.com/help/signal/examples/measuring-signal-similarities.html

Best regards from Hannover,

Mohammad

Dear Mohammad,

I appreciate your time and your detailed explanations. I think I should study more about the entire methods you introduced. Then I will come back to you again surely with more precise questions :)

And one more question raised in my mind about the cross-correlation analysis between the time series in the mathwork page is:

Can I use this method when the measuring devices measure different parameters (for example one of them measure aerosol content through the atmosphere and the other measures the solar radiance) ?

Thanks

Best regards,

Sahar

I should edit the answer for the accuracy we need. Our aim for the synchronization is in the order of milliseconds