I downloaded aerial LAZ files from the USGS 3DEP website but cannot seem to find any mention of trajectory files there.
Does anyone know if/where these can be obtained?
Thanks,
Rod
Thanks Oto,
Apparently they require trajectory files from their vendors but several fruitless phone calls and unanswered submissions to their support site seem to indicate they don't re-distribute them. I stumbled on a USDA Forest Service paper that describes a possible workaround and also mentions this:
“…these [trajectory files] are often excluded from the products delivered to the client and their recovery after the contract is complete can require negotiations with the data provider, may involve additional costs, or even be infeasible.”
“Even when trajectory data are included in deliverables, they are not necessarily in the projection of the raw return data. Many vendors have an established data processing workflow based on a projection of choice that is applied across their entire area of operations. All intermediate data products are organized in the preferred projection and are converted to the projection desired by the client just prior to delivery. Reprojection of the trajectory data to match the rest of the deliverables is often neglected.”
It mentions algorithms which can recover trajectories from existing point clouds by analyzing them. Also some other mesh generation software produce nice meshes even without trajectories so should be so critical.Other option to recover trajectories is from FL24 or similar but unfortunately full archive is not kept in these services and again need metadata.
Same issue in our region raw trajectories are not provided and only some ESRI SHP files with flight linework which are not so useful. Why so secret no idea, as it is just metadata and doesn't contain any sensitive info. Unfortunately trajecotories are not available in python API so it complicates even more so custom formats need to be manually converted and no automation.