SITE and OBJECTIVE: Lake Elaine is a 65 acre site in Southeast Flagstaff, AZ. The site features a drained lake that is surrounded my multiple residential structures in a ponderosa pine tree forest. Objectives for this project were to capture aerial imagery to create an orthomosaic image, and produce mass points and break lines so that the client (a local surveyor) could produce a topographic surface for further engineering design work.

WORKFLOW: The surveyor set 10 Ground Control Points (GCPs) throughout the Area of Interest (AOI). The AOI was then flown and Structure from Motion (SfM) processing was used to create a GEOREFERENCED point cloud. That point cloud was then classified into ground and non-ground points, from which mass points and breaklines are created. This workflow produces much more accurate and efficient (in terms of file size) surfaces than other methods.

ACCURACY: Pretty point clouds are nice to look at, but what really matters is accuracy of data. The surveyor shot a number of additional points on the site which we used as check shots to test data accuracy. Client requirements for this site were for 1-foot contours. However, this dataset has an elevation accuracy at the 95% confidence interval of 4-inches, meaning that the data could be expressed with 8-inch contours per NSSDA standards.