5.13.2. Based on internal geometry

The internal geometry of design of a space-borne multispectral sensor is quite different from an aerial camera. Figure 5.19 shows six types of remote sensing sensor systems; digital frame area array, scanning mirrors, linear pushbroom arrays, linear whiskbroom areas, and frame area arrays.

This chunk discusses the different configurations and types of remote sensing sensor systems based on their internal geometry. The primary focus is on how the design of space-borne multispectral sensors differs from that of aerial cameras. It mentions six types of sensor systems, detailing their distinct characteristics. Some employ pushbroom technology where sensors capture each line of imagery at a time, relevant to the position and movement of the sensor.

Imagine comparing a digital camera that captures full images at once (similar to frame area arrays) to a scanning device that records one line of data at a time (like a pushbroom system). Just as a printer scans a page line by line, these sensors collect data incrementally rather than all at once.

The geometric distortions in the images, such as skew caused by the rotation of the Earth, are required to be corrected before analysing the imagery.

This chunk emphasizes the necessity of correcting geometric distortions in remote sensing images before analysis. Geometric distortions can result from various factors such as the Earth's rotation, which can skew or misalign the captured images. The accuracy of the analysis heavily relies on these corrections to ensure the images reflect the true position and characteristics of the Earth’s surface.

Think of taking a photo of a moving vehicle. If you don't hold your camera steady, the photo might appear blurred or tilted, making it hard to identify the car's actual shape or position. Similarly, in satellite imagery, these distortions can misrepresent land features unless corrected.

Several air-borne systems, like Leica ADS-40, ITRES CASI, SASI, and TABI also employ pushbroom technology where each line of imagery is captured at a time, corresponding to an instantaneous position and attitude of the aircraft.

This chunk describes the use of pushbroom technology in various air-borne remote sensing systems. In these systems, imagery is captured line by line, which means that data collection corresponds to the real-time position and orientation of the aircraft. This method ensures that images are collected accurately and efficiently.

Consider how a robot vacuum cleaner works. It moves methodically across your floor, cleaning one line at a time rather than rushing over the entire room at once. Similarly, pushbroom scanners gather image data systematically, ensuring no areas are missed and that the collected information is precise.

The internal geometry of images captured by space-borne scanning systems is much more complex. Across-track scanning and whiskbroom systems are more similar to a LiDAR scanner than to a digital array sensor.

This chunk discusses the complexity involved in the internal geometry of images captured by scanning systems. Across-track scanning and whiskbroom systems capture images with a level of complexity that requires detailed registration of multiple pixels over different times, relying heavily on precise alignment to produce an accurate multispectral image.

Think about a pieced-together collage made of pictures, where each photo captures different moments and angles. If those pictures aren’t aligned correctly, the overall image looks chaotic and misleading. Similarly, without precise registration and corrections, the data gathered from complex scanning systems can lead to inaccuracies in remote sensing images.

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