For anyone contemplating a flight under a bridge without VLOS, don't forget there is almost a 1/4 second (typically 200ms) lag in your display, versus reality. You have to line yourself up really good because your reactions to correct any drift could be too slow to compensate in tight quarters. That's the downside to digital video communications. Consider, the video image compression at the camera > transmission to ground > receiving the signal by the RC > decompression of video packets by Go4 app > then displaying the video to the tablet. All this takes some time, about 180-220 milliseconds, which is amazing to me. The benefit of digital transmission is the range capability, along with video clarity on the display, virtually no snow (when in range). The distance doesn't affect this timing hardly at all, it's the compression and decompression that creates this lag.
DJI knows this lag needs to improve, and I believe they will continue to improve Lightbridge in the future. I believe this has improved with Lightbridge 2 (which is used in their high end drones), they claim 50ms, but I don't believe it. I read that Mavic's Ocu-Sync has reduced transmission lag also, but I haven't measured to confirm the numbers yet. I assume P5 will be upgraded to Ocu-Sync to be compatible wirelessly with the DJI goggles, and have less lag.
This is different than race quads that use analog video communications, which have no compression or decompression steps for transmission, hence the lag is only a few milliseconds. You virtually get real time control of the drone through the goggles, which is essential when navigating a drone at speeds of 80mph. The downside is less resolution, snow in the video feed, and less range capability.