I forgot to mention you could also perform terrestrial laser scanning or SLAM underneath the bridge and fuse those together with the aerial photogrammetry to ge

I forgot to mention you could also perform terrestrial laser scanning or SLAM underneath the bridge and fuse those together with the aerial photogrammetry to get a unified model, but this is even more effort and more post process. I have to wonder at what level you want a truly accurate representation of all bridges so that anyone could see them. Bad actors can ruin a lot of cool stuff.