GPST vs UTC while geotagging in PPK

Hi Forum,
We are flying a drone with an M2 strapped to it and we want to geotag a bunch of images that have milisecond-level UTC-0 timestamps (tagged by a local gps-ntp-server). We also have an RS2+ on site for the usual PPK setup.
Now I’m learning, that all RS2+ and M2 are logging in GPST:

A)
I’m understanding from the forum here that in PPK, EMLID will convert GPST to UTC-0 in EMLID Studio and geotag UTC-0 images correctly. Is that true?

So that would mean, if I’m PPKing with EMLID studio, I can just trow in my UTC-0 Images, but…

B)
…in case we resort to geotagging the images without EMLID Studio, e.g. via the LLH, we will have to do the GPST-UTC-Conversion by ourselves?

C)
Could someone from EMLID confirm that the M2’s and RS2+'s LLH is “still / also” in GPST, like @kseniia.suzdaltseva says here Weird time difference between dji drond and M+ ?

Sorry for insisting on confirmation, but we have quite a complex project and we really need millisecond level alignment of our images to the drone position.

THANKS!

PS: it’s NOT traditional Photogrammetry, so nevermind tipps like "“use GCPs” for this one :wink:

Hi @sunny.droneman,

I can confirm that the Emlid Studio output files are in GPST by default. The raw data logs from the Reach devices are in GPST as well. So, you are correct that the M2 and RS2+ LLH files are also in GPST.

in case we resort to geotagging the images without EMLID Studio, e.g. via the LLH, we will have to do the GPST-UTC-Conversion by ourselves?

Yes, you need to consider the leap seconds, which are currently 18 seconds.

However, it’s worth mentioning that the LLH is the track of M2 during the entire flight duration. Thus, the LLH coordinates would be more than the number of images. You would need to automate the process to determine which LLH coordinates are closest to when the photo was taken.

But Emlid Studio drone data processing will do this for you.

1 Like

Hi Ruth, great, thanks for the clarification!

Yes, if we do use the LLH later on, we would pick two appropriate points in time to interpolate the location of our M2. It might be useful for a higher level of automation going directly through the LLH, but we haven’t fully thought it through yet.

For now, EMLID Studio is a great tool to get up & running fast!

One more thing, while we’re at it: is the antenna height subtracted before or after logging the position in the LLH? according to the logic from above, the LLH is probably logging the antenna position without offset, right? :thinking:

Vincent