I've been doing more testing lately, specifically for an issue I've noticed with the camera not firing consistently in photogrammetry mode with my Inspire 1 Pro and 25mm lens. I created a simple route with one leg up and back, then ran that in the simulator using different flight speeds.
According to the calculations, this particular route would require 122 images, using the auto by distance option. I'm shooting in Shutter priority and using a fixed shutter speed of 1/1250. The Calc. Photo Interval is how often I expect the camera has to fire. Here are the speed results:
Speed Frames Taken Calc. Photo Interval
12 m/s 88 1 per 1.73"
10 m/s 100 1 per 2.08"
8 m/s 116 1 per 2.6"
6 m/s 118 1 per 3.47"
Even at 6 m/s, it appears to be missing some images. I've done tests with the Inspire 1 on my desk, manually taking photos using the DJI Go app every second without any issues, so I know the camera and my SD card are capable of capturing and storing data at that rate.
I also did another test with the above photogrammetry path, this time using the photo by time option, setting it to one photo every 1.5". That should have yielded 138 photos, but only took 72. I can't figure out where the issue is. The hardware seems perfectly capable. If it were a GPS issue, where delays in calculating the current position and deciding when to take the next photo were at play, then wouldn't that be ruled out with the photo by time test?