RTK survey is widely used for mapping projects. RTK survey results in a horizontal accuracy of about 2cm and about 3cm vertical accuracy. The most common one is using RTK GPS techniques, as it is the fastest and least expensive. There are two techniques to survey ground control points. On these images, the user can pick any visible ground feature (such as a parking strip or edge of where the concrete meets the asphalt pavement on a bridge) to use as a control point. The rightmost images represent different types of photo identifiable ground control points. The leftmost image In Figure 7.9 represents a pre-marked control point set on black and white fabric, while the image next to it represent a pre-marked control point that is spray-painted on a sidewalk. Many projects make use of one type or the other, or a combination of the two. This type of control also does not need to be surveyed before the UAS flies the project as it can be surveyed later on however, if temporary markers that can be disturbed or moved are used, they should be surveyed ahead of time. Pre-marked (Panels): This type is generated by marking or painting certain figures or symbols on the ground before the UAS flies the project (the left two images of Figure 7.9).This type of control does not need to be surveyed before the UAS flies the project, as it can be surveyed later on. Photo Identifiable (Photo ID): This could be any feature on the ground such as a manhole, parking stripe, etc.There are two standard types of ground control points (Figure 7.9), those are: Accurate, well-placed ground controls are essential elements for any photogrammetric project utilizing aerial triangulation. In this section, we will discuss an important topic to any photogrammetric work: ground controls.Ī ground control, which we introduced in the last section, is a target in the project area with known coordinates (X,Y,Z).

Ground control points