From the blog of the Pixahwk-compatible high-accuracy Reach RTK GPS
Reach was built with precision mapping applications it mind. One of the big challenges in UAV mapping is eliminating Ground Control Points which are time consuming and costly to place. Reach RTK can help achieve that by synchronizing with the camera shutter on sub ms level. I have written more about this in a previous post. All you need to do is connect hotshoe adapter to your camera and wire it to Reach port. Only two connections are required "GND" and "Time Mark":
At top is how @timvand did it with his Sony A6000.
During RINEX conversion on Reach you will see a new field that will show how many time marks have been collected. That should match the amount of pictures taken by the camera.
Those of you who have access to GrafNav can already start mapping and getting accurately georeferenced pictures. Thanks to @Stu74 we know that it parses time marks from RINEX and interpolates the post processed coordinates.
We have also implemented this feature in RTKLIB and will release modified RTKPost soon.
Emlid is going to make right what is broken about UAV mapping.