To ensure their results were accurate, the NDOT team used both ground control points and check shots.

The aerial targets were surveyed using a Trimble R10 RTK rover using a cellular modem to connect to a Virtual Reference Station. The site was georeferenced based on six monuments and the survey points were converted to State Plain coordinates (NAD83 Nevada West) in US Feet.

The configuration of the GCPs were varied in order to observe the change in accuracy, and to compare the point cloud with respect to GCP density and location.įigure 2: Image locations for the 318 images, taken in 8 flight lines. In total, over 15 computations were created and their root mean squared error (RMSE) values were compared. GCPs that were not used to georeference the project were used as check points to compare the reconstruction to the real-world values. The imagery was collected using a DJI Phantom 4 Pro, processed in Pix4Dmapper photogrammetry software, and point cloud products were georeferenced using 0 to 18 GCPs. The site is bordered to the southeast by Highway 50, and to the remaining sides by undeveloped sagebrush habitat.Ģ1 ground control points were arranged throughout the project site and surveyed using a Trimble R10 RTK rover connected to a VRS system over cellular radio. There is approximately 180 feet of vertical relief between the highest and lowest ground control shots. The 34 acre site measures approximately 2,000 feet long and 900 feet wide. Project informationĪn active Nevada Department of Transportation quarry was selected as the test site. To test how many GCPs are really required for accurate results, the team set out a series of tests. For example, RTK drones can give extremely accurate results without using any GCPs. But placing GCPs adds a lot of time, and the team had heard that in some cases GCPs may not be necessary at all. Because accuracy is vital, the team uses ground control points (GCPs) as a standard part of their workflow. Like many innovative government departments, the DOT uses drones for mapping. The Nevada Department of Transportation is responsible for the planning, construction, operation and maintenance of 5,400 miles of highway and over 1,000 bridges which keep the state of Nevada moving. Or does it? The Nevada DOT conducted a trial to find out. Adding more ground control points takes time but means more accurate drone maps.

Global mapper 11 blogspot