Such relations not only enable us to compute the ground coverage of a photograph (image) but also enable us to compute the scale of such a photograph or image. From such geometry, the film four corners a' b' c' d' cover an area on the ground represented by the square ABCD. In Figure 4.3, ground point A is projected at image location a' and ground point B is projected at image location b' on the film. This physical phenomenon enables us to express the ground-image relation using trigonometric principles. Source: Elements of Photogrammetry with application in GIS, 4th edition, 2014 McGraw Hill Scale of Vertical ImageĪs the sun's rays hit the ground, they reflect back toward the camera, and some actually enter the camera through the lens. In summary, a vertical image is an image that is either looking straight down to the ground or is looking a few degrees to either side of the aircraft. Therefore, vertical image definition allows a few degrees deviation from the nadir (the line connecting the lens frontal point and the point on the ground that is exactly beneath the aircraft). As the aircraft moves, so does the camera, and this makes it impossible to take a true vertical image. By vertical photograph or image, we mean an image taken with a camera that is looking down at the ground. oblique photography: between ☓5º degree and ±55º off nadirįor the purpose of this course, we will focus only on the first two types, and that is vertical and near-vertical photography.įigure 4.3 illustrates the basic geometry of a vertical photograph or image.tilted or near-vertical photography > 0º but less than ☓º – Most used –.true vertical photography: ☐º from nadir.
In photogrammetry, we usually deal with three types of imagery (photography), They are defined in term of the angle that the camera optical axis makes with the vertical (nadir), those are: Therefore, it is essential to the work of the flight planner to have all of this information understood and available before starting to design a mission. The size of the CCD array and lens focal length coupled with flying altitude (above ground) determines the image scale or the ground resolution of the image. In order to understand mission flight planning, you need to understand the geometry of the image as it is formed within the camera.
0 kommentar(er)
