![]() Absolute AccuracyĪbsolute accuracy is how accurate the items are in relation to their position on Earth. The use of Ground Control Points could improve the absolute accuracy. ![]() (Learn more about ground sample distance.) This aerial survey appears to have a low level of absolute accuracy because the images do not line up with the base map. Relative accuracy will usually fall within one to three times the ground sampling distance. If the measurements between the buildings in the images were the same as in the real world, the relative accuracy of the project would be high. For example, imagine an aerial survey with two buildings. Relative accuracy is how accurate points within a project are in relation to each other. To understand how GCPs improve the accuracy of an aerial survey, it is important to understand the difference between relative and absolute accuracy. ![]() Two kinds of accuracy are relevant to data gathered by drones for surveying. How Do Ground Control Points Improve Drone Survey Accuracy? Additionally, the center point provides an exact point that can be measured. A checkerboard works well because it is high contrast and easy to see in the image. Commonly, GCPs have a checkerboard pattern or some kind of target with a defined center point. So what exactly is a Ground Control Point? Anything that is easy to see in an aerial image can be used as a GCP. Ground control points ensure the accuracy of these outputs by linking the latitude and longitude of a point in a photo to an actual GPS coordinate on the ground. ![]() After a flight, the software processing turns photos and geodata into orthomosaics, 3D models, digital elevation models, or other outputs. Ground Control Points (GCPs) are physically defined points on the ground, with known coordinates, that are visible in the photos. The high contrast is easy to see in images and the center point is easy to define.ĭuring an aerial survey, drones collect photos and geographic data. What is a Ground Control Point? A typical example of a Ground Control Point with a checkerboard pattern. ![]()
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