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Lynn, Point cloud from Agisoft issue in Cloud Compare is a scaling issue. See this discussion from the Cloud Compare Forum. http://www.danielgm.net/cc/forum/viewtopic.php?t=2804 I'm still learning CC, but had the same problem with opening Agisoft PC in CC. Cheers, Dave On Sat, Aug 4, 2018 at 10:45 AM, [log in to unmask] < [log in to unmask]> wrote: > This is primarily a visual exercise (viewsheds) so error in the > transformation of elevations from drone measure to real world measure is > acceptable and expected. Just want to get to roughly the right z values as > grad student is working on thesis (and perhaps publications). The points > are pretty much spot on in xy space. All the data were collected on the > same day; over the course of approx. 7 hours. > > Area of interest is +- 300,000 square meters small enough that we are not > concerned with curvature of the earth surface. Also found out that the > origin is different than what I was given before – so take off location and > altitude of the drone is: > 38.8 m Above Sea Level > 33 deg 57' 19.93" N > 35 deg 35' 49.15" E > > At this location, using Google Earth for a ground control point (thanks > for the suggestion Dave Tewksbury), the elevation is +- 28 meters. > The point cloud elevation at this location in the .las file is -90.093 > As others have suggested, should be simple math (!), but just taking the > home point elevation and trying to adjust the point cloud elevation based > on that does not work. > > Home point = 38.8 meters Above Sea Level > Point cloud elevation at Home point = -90.09 meters > Real Elevation (approximate from Google Earth but the only thing I have to > go on) = 28 meters > > Add home point to point cloud elevation gives -51.293 meters nowhere near > 28 meters not to mention still negative. > Tried following as well – took several locations and found their real > elevations (again approximate from GE) to use as GCPs > > (-90.093) x (Y) = 28 > Solving for Y > 28/-90.093 = -0.3107 > > At a second location in the study area > 33 deg 57’ 17.09” N > 35 deg 35’ 43.24 E > > At this location, using Google Earth for a ground control point, the > elevation is +- 32 meters. > The elevation at this location in the .las file is -73.592 > > Applying the same math > (-73.592) x (Y) = 32 > Solving for Y > 32/-73.592 = -0.4348 > > This seemed promising – maybe the conversion is somewhere around -0.5 give > or take > But then: > At a third location in the study area > 33 deg 57’ 21.16” N > 35 deg 36’ 7.81” E > > At this location, using Google Earth for a ground control point, the > elevation is +- 77 meters. > The elevation at this location in the las file is -12.992 > > Applying the same math > (-12.992) x (Y) = 77 > Solving for Y > 77/-12.992 = -5.927 > > Way different than the other two > I tried with four or five more GCPs and each time came up with very > different Y values, so there is not a consistent one I can use across the > entire point cloud. > > Then I tried opening in Cloud Compare (thanks Neil Olson for suggestion – > I had forgotten about this app). It does not open correctly but rather in > a long single strip. Makes me think some important value is being > transposed? Not sure…since I cannot “see” it, I cannot bring in the text > file of GCPs to do point matching. > > Conclusions so far: > - I am not using my GCP elevations correctly (bad math) > - Maybe over the course of the day, the drone’s home point was reset > (I do not know) and Photoscan is able to adjust for this and stitch the > data together to produce an .las file that is correct relative to itself. > If so, maybe there is metadata in Photoscan that will say what the > adjustment was? Sadly I cannot check as I do not have access to the > software, only the output .las file > - Something about the coordinate system? XY are in decimal degrees, > Z in meters. Not finding a tool in ArcGIS to project the .las file….will > explore further. > > Biggest conclusion: > NEARC folks are the best (although I already knew this). Thanks so much > to everyone for the help. > > ------------------------------------------------------------------------- > This list (NEARC-L) is an unmoderated discussion list for all NEARC Users. > > If you no longer wish to receive e-mail from this list, you can remove > yourself by going to http://s.uconn.edu/nearcsubscribe. > -- Dave Tewksbury FAA Certified UAS Pilot GIS & Tech support Dept of Geosciences Hamilton College Clinton, NY 13323 USA ------------------------------------------------------------------------- This list (NEARC-L) is an unmoderated discussion list for all NEARC Users. If you no longer wish to receive e-mail from this list, you can remove yourself by going to http://s.uconn.edu/nearcsubscribe.