I know little about the subject but, whilst a little old, this thread suggest there may be : Open Drone Map - a serious alternative to Pix4d
Also this search will take you to several thread where there may be relevant info.
I know little about the subject but, whilst a little old, this thread suggest there may be : Open Drone Map - a serious alternative to Pix4d
Also this search will take you to several thread where there may be relevant info.