One of the primary products for Survey Mapping is a rectified orthomosaic. A rectified orthomosaic can be used as a background reference for creating 2D planimetric linework in a CAD platform.
A rectified orthomosaic is produced from multiple images taken along controlled flight lines at the right amount of front and side overlaps. My series of books on
Survey Mapping Made Simple
covers all of the details needed to plan missions that will capture the images correctly.
It is important to have a good multiple image neat area splicing solution when creating a rectified orthomosaic. The method to create a rectified orthomosaic from the flight data will be different between software platforms.
I have used Pix4D and Dronedeploy which does an excellent job in splicing the imagery.
I currently use Metashape Pro which has a easy to follow workflow to create a rectified orthomosaic.
I have experimented with different settings to see what produces the best rectified orthomosaic.
I have used a Sparse Point Cloud which is the quickest method. Any object that is elevated such as a fence, buildings, walls, covered parking structures, etc. will be somewhat distorted and unreliable for producing 2D planimetric linework as shown in the image 1 below.
The cleanest method is to use a high density 3D Mesh to control the rectified orthomosaic. This process takes the longest however the elevated structures are much cleaner as shown in image 2 below.
The method I use the most is to create the rectified orthomosaic from a Dense Point Cloud as shown in image 3 below. This method takes a while depending on the computer hardware and the number of images that need to be processed. It produces a rectified orthomosaic that is really close to the one produced using a 3D Mesh.
