Discrepancies in number of images taken and estimate

A little more digging into the .csv flight logs...

The October flight (85% front overlap/90% side overlap; 1800 photos) looks like it was taking images every 2.03 seconds (the mean time difference between rows in the .csv file when the App_Tip column records a "DJI_XXX.JPG" image captured). The mean speed when those images were captured was 7.2 m/x.

Last week's flight (89% front overlap/90% side overlap; 1100 photos) looks like it was taking images much slower-- every 3.03 seconds and at only 6.7 m/s on average.

I do think I adjusted the SD card speed to the faster setting for last week's flight (1 image every 2 seconds instead of 1 image every 2.5 seconds like October's flight), which I would have thought would make it take pictures faster.

What else might result in photos being taken less frequently? Both days were bright and clear. I assume the shutter speed and ISO settings were the same, but I will check that next...

EDIT:

It looks like ISO was 100 for each flight, but the exposure time was faster for the October flight (1/402 on average versus 1/214 on average last week). Would this be enough to slow down the frequency of camera capture?

Okay, so the number of images should be treated as an estimate. Fair enough!

That must have changed since your comment a year ago: "The number of images taken are carefully calculated based on the overlap , altitude, and speeds that are defined by the user. They are pretty accurate. We don't know what other apps do but our number is quite solid." [https://support.dronesmadeeasy.com/hc/en-us/community/posts/115000313283-Number-of-Images]

The flight logs suggest the aircraft firmware was the same for each flight: 1.3.1.00

The camera and aircraft were the same for each flight-- a Zenmuse X3 mounted on a Matrice 100.

The SD card is a SanDisk UHS Speed Class 3 (U3), so it should be fine to write 1 image per 2 seconds instead of 1 image per 2.5 seconds. And it wrote that fast in October (1 image every 2.02 seconds on average).

The speed of the flight doesn't seem to be the issue-- it was pretty similar both times. It seems to be in the triggering of the images themselves.

I learned from here [https://support.dronesmadeeasy.com/hc/en-us/articles/217006946-Connectionless-Mapping] that Distance Triggering isn't possible with my aircraft, so it must be doing Timed Triggering.

The camera was on Auto Exposure both times (and exposure was a bit longer when fewer photos were taken, but just fractions of a second longer. I wouldn't think this would cause a 1 second delay in triggering every image).

So it seems like it's something with Timed Triggering. A photo every 3 seconds versus one every 2 seconds is pretty significant. What can I do to change this timing?

Ha! Straight from the horse's mouth...

Terrain may affect things but timed triggering for connectionless mode will definitely affect things. 

If you have the log files you can email them to us for a look.

Thanks! An extra set of eyes on the flight logs would be super helpful. What is the best email to send them to? You just want the .csv files?

Some more thoughts... 

Please use AirData to visualize what is going on here in a better format. Have you checked the actual number of images that get written to the SD card and compared that with what is showing up in the log file. The lines in the log file that say what images got written are not getting written sequentially, there are gaps. The DJI_XXXX.JPG entries in the log file are not guaranteed to get there. For some reason they don't all show up but since it is operating in connectionless mode the triggering is happening on the aircraft and the files seem to be getting written. If they are not, that is a different issue. 

Look for images on the SD card that are not listed in the Log File. 

It also looks like aircraft that are being triggered by distance on the aircraft treat passing through a waypoint differently. Some reset the distance measurement and others don't. The result here is longer gaps after passing through a waypoint and if you have a super complicated linear mission it will have more gaps in it as it goes through all the waypoints. 

Wow! Was this patched in 2.8.1?? Is that what the "Fixed the Connectionless interval imaging on older cameras" refers to?

You all are amazing.

We hope so. Since the camera intervalometer can only be set to integer seconds (which is extraordinarily dumb) we adjust the aircraft speed downward to get the overlap to work with the quantized timer settings.

Let us know how it works for you.

YES! Excellent work and thank you for making this patch available. By slightly adjusting the flight speed in the way Map Pilot 2.8.1 calculates necessary speed for a given front overlap,  I now get image capture every 2 seconds instead of every 3 seconds. I was getting about 1300 images before, and now get about 50% more (about 1900). In Map Pilot 2.7.4, 90% front overlap with the X3 camera used to set flight speed at about 6.7 m/s, and now 90% front overlap sets flight speed to about 6.3 m/s.

Missions are now negligibly longer, and way more photos are taken. Perfect.