Scale and Area Measurement. Optical remote sensing - Coastal Wiki. This article provides an introduction of optical remote sensing techniques. This technique can be used to detect all kind of in-water properties. This article describes the general principles of optical remote sensing, the way data can be processed and the restrictions with respect to the application of optical remote sensing. Introduction Remote sensing using satellite and airborne sensors is a powerful, operational tool for monitoring coastal zones. This technology can provide accurate, large-scale, synoptic environmental information essential for understanding and managing marine ecosystems.
Optical multi- or hyperspectral sensor data allows the assessment of in-water properties, such as suspended matter or phytoplankton concentration, benthic substrate type, vegetation composition, and bathymetry in (optically-)shallow waters. Principles In marine and aquatic environments, the sunlight spectrum is modified on its way through the atmosphere, the water surface, and the water body. Numbering, Scale, and Indexing Aerial Photographs.
Each aerial photograph contains in its margin important information for the photo user. The arrangement, type, and amount of this information is standardized; however, the rapid development of cameras, film, and aeronautical technology since World War II has caused numerous changes in the numbering and titling of aerial photographs. As a result, the photo user may find that the marginal information on older photographs varies somewhat from the standard current practice. With certain camera systems, some of the data are automatically recorded on each exposure, while other systems require that all titling data be added to the film after processing. Before a photograph can be used as a map supplement or substitute, it is necessary to know its scale. On a photograph, the scale is also expressed as a ratio, but is the ratio of the photo distance (PD) to ground distance.
Figure 8-8. Figure 8-9. Figure 8-10. Figure 8-11. Figure 8-12. Figure 8-13. Figure 8-14. Return to Aerial Photographs. Sonar_introduction_2010. Registration of Stereo Pairs and the Stereo Window. In this chapter we outline the theory of registration and the stereo window. This is followed by a discussion of some tools to help get it done efficiently and effectively. The emphasis here is on making prints for viewing, or making stereo pairs for the web. Registration methods for projection are discussed in chapter 7, though the basic theory is discussed below. Before presenting a stereo pair it is necessary to align the images carefully. Film slops around inside film cameras (unless you use a very specialized scientific-grade pin-registered camera).
Images from twin digital cameras may be skewed by camera mounting errors or by individual cameras that have their CCD's in slightly different positions, for example. This misalignment of the images can cause severe eye strain and make it difficult to fuse the image pair, no matter what the presentation technique. Here is a simplified discussion of registration. Fig. 5.1 Image Registration Horizontal Translation in x. Vertical Shift in y. Tutorial: Fundamentals of Remote SensingMicrowave remote sensing - Radar Polarimetry.
Introduction to GIS. Volume 1, Lecture 6. Considering that most aerial photographs are not perfectly vertical, there are three different photo centers: the principal point, the nadir, and the isocenter. Each one of these centers plays a specific role and is of great importance to the photogrammetrist because different types of distortion and displacement radiate from each of these points. Theoretically, if an aerial photograph is perfectly vertical, the three centers coincide at one point (i.e., the principal point), which is the geometric center of the photograph defined by the intersection of lines drawn between opposite fiducial marks (figure 6.6). The principal point is the optical or geometric center of the photograph. It is the image of the intersection between the projection of the optical axis (i.e., the perpendicular to the center of the lens) and the ground (figure 6.6).
The principal point is assumed to coincide with the intersection of the x and y axes. Geometry of Aerial Photography. I. Classification of Photographs In his book on aerial photo interpretation, Paine presents a dichotomous key for classifying aerial photography. The key is listed as follows: Photographs Terrestrial Aerial Vertical Oblique True Tilted High Low We can define vertical aerial photographs as a photo taken from an aerial platform (either moving or stationary) wherein the camera axis at the moment of exposure is truly vertical. 1. 2. In a high angle oblique, the apparent horizon is shown; while in a low angle oblique the apparent horizon is not shown. The basic advantages of vertical air photos are: 1. 2. 3. 4. The advantages of an oblique aerial photograph include: 1. 2. 3. (Paine talks about clearance and cloud cover; but that's a tricky one (too cloudy for vertical but maybe enough clearance for an oblique).
Three terms need defining here, they are Principal Point, Nadir and Isocenter. 1. 2. 3. On a true vertical aerial photograph all three of these would be at the same point. A quick review. II. Tutorial: Fundamentals of Remote SensingMicrowave remote sensing - Airborne versus Spaceborne Radars. Like other remote sensing systems, an imaging radar sensor may be carried on either an airborne or spaceborne platform. Depending on the use of the prospective imagery, there are trade-offs between the two types of platforms. Regardless of the platform used, a significant advantage of using a Synthetic Aperture Radar (SAR) is that the spatial resolution is independent of platform altitude.
Thus, fine resolution can be achieved from both airborne and spaceborne platforms. Although spatial resolution is independent of altitude, viewing geometry and swath coverage can be greatly affected by altitude variations. Although airborne radar systems may be more susceptible to imaging geometry problems, they are flexible in their capability to collect data from different look angles and look directions. As with any aircraft, an airborne radar will be susceptible to variations in velocity and other motions of the aircraft as well as to environmental (weather) conditions.