I’m confirming the accuracy of using UAS and Pix4DMapper for our road projects in anticipation of using aerial photography for our hard surface mapping. I was able to successfully create a point cloud and the necessary files to import a DSM into Civil 3D. At first I wasn’t too pleased with my results. I used 21 GCP’s over a 1.5 mile project and had them located with RTK GPS. I selected the proper state plane coordinates for my output files however; when I imported the “dsm_100cm.xyz” over a project which was completed with total station, I found that my elevation was a consistent 0.40’ off. But, if I reviewed the coordinate in the rayCLoud editor they are right on! If I applied a manual -0.40’ to the dsm in civil3D everything matched great! I was surprised to see my data within a 0.07’ of our total station locations. This is an amazing result, but I’m concerned about why I had to apply a manual shift.
My question is: How come in the rayCLoud editor my elevations are perfect, but yet when I import the dsm surface into CIvil3D those same elevations are shifted 0.40’?