slide 23

In nature, saw images have geometric distortions. There are three types: full shortening, layover, and shadow. Full shortening occurs when the radar beam hits the base of a mountain first, then the top later. This makes the length between the base and top appear compressed in the saw image. Layover happens when the radar beam hits the top before the base, causing the top to overlap the base in the image. Shadow occurs when the radar beam cannot hit an object, creating a shadow behind it. Going to the side look in nature, the saw images have some geometric distortions. There are three types of geometric distortions in saw images. Full shortening happens when the radar beam first hits the base of the mountain and then hits the top later. The measured length range is shorter than the real length between base and top of the mountain. So, on the saw images, the length between base and top is compressed. You can see the case of AB. The doped blue line is the radar beam. Dashed blue line is the projection line on the slant range. The solid blue line is the slant range. You can see the length between A' and B' is shorter than the real length between L and B. C and D is the extreme case for shortening. The base and top are imaged at the same time. So, C' and D' coincide in the slant range, which means they are in the same position in the saw image. Layover happens when radar beam hits the top earlier than hits the base. So, in the slant range, the top is closer to the base. In other words, on the saw image, the top layover the base. You can see the case of EFF. Shadow happens when radar beam cannot hit the object. You can see the shadow behind the steep object, such as buildings or mountains. It is just like the case when sunrise cannot illuminate the shady face of buildings. You can see the gray area as an example.