Remote sensing techniques

None of the foregoing methods will tell the frequency or duration of exposure of any receptor to irritant or odorous gases when each such exposure may exceed the irritation or odor response threshold for only minutes or seconds. The only way that such an exposure can be measured instrumentally is by an essentially continuous monitoring instrument, the record from which will yield not only this kind of information but also all the information required to assess hourly, daUy, monthly, and annual phenomena. Continuous monitoring techniques may be used at a particular location or involve remote sensing techniques. 

List the advantages and disadvantages of remote sensing techniques by optical methods. 

Remote sensing techniques have been successfully applied for the identification of rocks in Cape Smith fold belt region. Principal Component Analysis is very effective for the separation of gabbro, metabasalt and peridotite. Band Ratio was helpful for the preliminary identification of peridotite. Supervised Classification approach is taken to verify the results obtained by Principal Component Analysis and Band Ratio. It is also useful to remap the unknown regions once the results are verified. 

Wert, S. L. A system for using remote sensing techniques to detect and evaluate air pollution effects on forest stands, pp. 1169-1178. In Proceedings of the Sixth International Symposium on Remote nsing of the Environment. Vol. 2. Ann Arbor University of Michigan, 1%9. 

It should be noted that scattering of light by particles can be measured using remote sensing techniques on satellites, from which such parameters as total aerosol optical thickness i.e., the exponent (bcxlL) in... 

In Sweden, three-way catalysts have been required on all cars since 1989, and tax incentives were offered to purchase such vehicles in the 1987 and 1988 model years. Figure 16.34 shows the CO and hydrocarbon exhaust emissions as a function of model year of gasoline-powered cars, measured using a remote-sensing technique (Sjodin, 1994). There is a large decrease in the emissions from 1987 to 1988 and 1989, supporting the effectiveness of these motor vehicle exhaust controls. 

A similar decrease of 18 + 11% in CO emissions attributed to the use of oxygenated fuels was reported by Johnson et al. (1997). They used remote-sensing techniques to compare CO from automobiles leaving Las Vegas, where oxygenated fuels were in use at that time in winter (1991/92), to that from automobiles entering from California, where these fuels were not then in use. 

The hatched region in Fig. 14.1 shows the approximate values of k at visible wavelengths inferred by various remote-sensing techniques (Grams et al., 1974 Reagan et al., 1980 and references cited therein). If we compare these values of k with those for individual constituents of the atmospheric aerosol, it seems... 

Cosmochemistry is the study of the chemical composition of the universe and the processes that produced those compositions. This is a tall order, to be sure. Understandably, cosmochemistry focuses primarily on the objects in our own solar system, because that is where we have direct access to the most chemical information. That part of cosmochemistry encompasses the compositions of the Sun, its retinue of planets and their satellites, the almost innumerable asteroids and comets, and the smaller samples (meteorites, interplanetary dust particles or IDPs, returned lunar samples) derived from them. From their chemistry, determined by laboratory measurements of samples or by various remote-sensing techniques, cosmochemists try to unravel the processes that formed or affected them and to fix the chronology of these events. Meteorites offer a unique window on the solar nebula - the disk-shaped cocoon of gas and dust that enveloped the early Sun some 4.57 billion years ago, and from which planetesimals and planets accreted (Fig. 1.1). 

Chemical analyses by spacecraft are spectroscopic techniques. Some techniques used successfully on spacecraft (X-ray fluorescence, mass spectrometers) have been discussed previously. Here we focus on some important remote sensing techniques that have not already been presented. 

One of the first examples of the modem application of remote sensing of the composition of the atmosphere was the assertion by Hartley in 1880 that the UV absorption in the solar absorption spectrum was attributable to ozone. In this manner the earth s stratospheric ozone layer was discovered. Since this pioneering work and especially in die past 30 years, there has been rapid progress in the development of atmospheric remote sensing techniques. 

Various instruments utilising remote sensing techniques to determine atmospheric composition are discussed in the sections. The characteristics of the different instruments and their objectives are summarised in Table 1. 

Table 10.1. Surface features of terrestrial planets measured by remote-sensing techniques... 

Reflectance spectroscopy has proven to be the most powerful and versatile remote-sensing technique for determining surface mineralogy, chemical compositions and lithologies of planetary objects, as well as constituents of their atmospheres. Table 10.1 summarizes information that has been deduced for the terrestrial planets based on spectral properties of light in the visible and near-infrared regions reflected from their surfaces. 

Andersen, K.L. (1978) Reflectance spectroscopy as a remote sensing technique for the identification of porphyry copper deposits. Ph.D. Thesis, MIT. 

Reading the above, one might get a pessimistic view of the possibilities of remote sensing techniques to derive the composition of cosmic dust in protoplanetary disks. However, when the limitations of the techniques are properly considered, it is possible to derive a wealth of information. The above limitations force one... 

In conclusion, (radial) mixing and the accompanying thermal processing of the grains are evident from both remote sensing and laboratory studies of protoplanetary dust. These mechanisms will be discussed extensively in Chapter 8. Further development of the remote sensing techniques requires accurate models of the optical properties and predictions on the aggregate shapes expected to form in disks. These will be discussed in Chapter 7. 

As is clear from several of the earlier sections, estimation of in the field is technically difficult and results are spatially and temporally limited. Some efforts have therefore been made to investigate whether remote-sensing techniques... 

Underwater remote-sensing techniques using an optical fiber cable have several advantages. Useful data on the in situ size distribution, concentration, and algal color group of phytoplankton in the marine environment may be obtained. Measurements at high speed can be carried out because the towed pressure vessel can be streamlined by limiting it to the optical... 

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