We collect thousands of photos from our municipality with our little drone and our goal is to create survey grade ortophotos and a presentable 3D model for the web. When adding the photos to Context Capture I assume camera data would be the same for all photogroups, but surprisingly they show varying focal length.
Camera data is listed in the database and should be fetched from there, so what causes the program to set different focal lengt to photos taken with the same drone camera at more or less same altitude all the time?
Am I worrying for no reasons, does the altered focal length affect any of our results, or is it just something to accept and forget?
Happy for any ideas!
/Anders Theodorsson, Ludvika Municipal GIS-data office
Thank you for the tip
Yes you would need to clear the focal lengths to group. Unfortunately there is no option to edit protogroup selection only each separately.
Hi Oto,
Same pb here with DJI camera for which various focal length are affected to same drone images.
Anyway, my pb is that I cannot group the photogroup as usual in iTwin Capture Modeler v 23.0.0.1659
Calibration is more or less random. It is not so important as adjusting focal length is way how software handles tie point connections. For example slightly blurry photos will also change calculated focal length while physically it is the same. Just enter some average fixed value and merge all photogroups. Software will do adjustments if necessary.
Answer Verified By: Anders Theodorsson
Okay, I get that every calibration gives different result because of the variation of focus adjustment. But then again, how does CC handle a single photogroup with drone photage where almost every single photo has a variation in focal length due to the autofocus constantly adjusting to the present motiv?
In some way it seems to do this and by that I don't get why one should ever have to calibrate and enter new values instead of the fixed values stated by DJI? The calibrated values I get from a calibration are more or less random depending on what photos I choose to use in the calibration process. I may pick 20 from the beginning of a flight, or from any other part of the same flight and by that get different values out of the process every time.
Maybe I shouldn't bother but instead just enter the fixed values from DJI and be happy with that?