Hi
I like to share a CHDK script, which combines both triggered by usb signal and by intervalometer.
The most popular script for UAV photomapping is probably KAP_UAV.lua that is certainly very useful. However, it is somewhat too much for works that don't have to adjust exposure condition for every photo and don't shoot video. I found out that when triggered by intervalometer, it can only take photos every 5 seconds or longer. Even we set time interval to be 3 or 4 seconds, the camera (Canon S100) still takes photos every 5 seconds. Guess this is because the camera needs several seconds to interpret the script.
CHDK site provided a short script for intervalometer. But trigger by distance is a better way to do photogrammetry because photos will distribute more evenly. Event38 provides a short script for triggering by usb signal, which is really convenient for Do-Cam-Trigg-Dist shooting. But the command occasionally fails to send out the signal (see attached image). Not just me, I found other people reported problems about Do-Cam-Trigg-Dist on this forum. There are times that the camera stopped shooting after a missing shot.
So we write a short script that combines Event38's usb-trigger script and the intervalometer script on CHDK site. It will read usb signal first, and if no signal for an extended period of time (set by user) for whatever reason, it will shoot a shot (as an insurance), then wait for next usb signal. You can also end the do-cam-trigg-dist in middle of the mission, or shift between usb-trigger and time-lapse trigger. I have tested in flight. The result is the attached image. We use do-cam-trigg-dist in the begging then change to intervalometer. We set the interval to be 10 seconds, so it's easy to see the difference. In real work, we probably will set the time interval 2 or 3 seconds longer than the estimated time (from distance and speed).
Feel free to modify it to fit your need, and share with others.
Shouyeh
2017_01_19_distance%20or%20interval_test_%E5%8C%97%E5%B1%AF.jpg
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