Band Ratio

The band ratio minimizes the effect of environmental factors like slope and aspect, shadows or seasonal changes which affect the brightness valnes of an identical surface. The band ratios provide unique information that is not available in any single band. The mathematical expression of the ratio function is  

Normalization is done to eneode the values in a standard eight bit format. Using the normalization function the ratio value 1 is assigned the brighmess value 128 and the ratio values between 1/255 and 1 are assigned values between 1 and 128 by the function  

Ratio values from 1 to 255 are assigned values within a range of 128-255 by the function 

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These authors detected the vibrational bands of reactive acrylate groups from a measuring volume of 1 pm3, and calculated reaction conversions from reactive band ratios before and after curing (see Figure 3.9). 

The addition of Na also impacted the Pt-CO linear u(CO) to bridged u(CO) band ratio, referred to as L/B.52-53 The presence of the Na dopant favored an increase in the amount of bridge-bonded CO, where the ratio of 8.3 for no alkali doping decreased to 1.5 for the 2.5% Na-doped sample. Competing viewpoints (e.g., electronic, geometric) regarding the nature of the change in the L/B ratio are summarized in previous works.1-49... 

KEYWORDS Remote Sensing Geology, Landsat Enhanced Thematic Mapper, Band Ratio,... 

The Dumas Formation is uncomformably overlying the Archean Superior Province. It hosts metasediments and intercalated iron formations, as well as peridotite and gabbro bodies, which were identified and separated with the help of both Band ratio and Principal Component Analysis. 

Methods Results The flow diagram (Fig. 2) outlines the methods used for the review and separation of the rocks present in the area. Image enhancement is done to increase the variance in the dataset. Contrast manipulation, spatial feature manipulation, and multi-image manipulation are used as digital enhancement techniques (Lillesand et al. 2007). In this study multi-image manipulation is used, which includes Band Ratio and Principal Component Analysis. 

The Band ratio approach for the lithology identification was taken previously by many authors (Sabins 1999 Gad et al. 2005 Khan etal. 2006). 

The Band Ratio enhancement technique can be used to remove the brightness variation caused by topographic effects in a region. (Gad et al. 2005 NASA Remote sensing tutorial by Dr. Nicholas Short)... 

Two objects with different spectral properties, i.e., variation in the slope of spectral reflectance curve of two bands, can be separable with the help of ratio images (Lillesand et al. 2007). In this study standard reflectance data of USGS Spectral Library and John Hopkins University spectral library (Available in ENVI) have been used. To enhance the dissimilarity between different rock types in the scene, plots with a higher reflectance were kept in the numerator and plots with low reflectance were kept in the denominator, while taking the band ratios. Using this approach, a ratio of 5/3 was taken for basalt, 7/3 for peridotite, and 4/2 for vegetation. 

Figure 3 displays a Band Ratio image (5/3, 7/3, 4/2), in which peridotite appears dark yellowish black colour. It is difficult to distinguish between gabbro and basalt, due to their similar reflectance properties. 

In general, the spectral band ratio technique is helpful to identify the peridotite, but basalt and gabbro are not uniformly separable over the entire region. 

Fig. 3. Band ratio image of 5/3, 7/3, 4/2 as RGB false colour composite.

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. 

It has become clear in the past decade that strong hydrogen bonding has associated with it several characteristic properties. In particular, as hydrogen-bond strength changes, maxima or minima are observed in nmr chemical shifts, the isotope effect on the chemical shift A[5( H) — 8( H)] defined on p. 271, ir Vah/vad band ratios, and in the isotope-fractionation factor, p. 

One of the now-classic examples of process Raman spectroscopy is monitoring the efficiency of converting the anatase form of titanium dioxide to the rutile form by calcining [67-69]. The forms have dramatically different spectra, enabling simple univariate band ratio models to be used. The uncertainty in the mean... 

Landsat imagery was downloaded from the GloVis viewer (http //glovis.usgs.gov/). The data were atmospherically and geometrically corrected. Band ratios were used to map the presence of iron oxides, hydroxides, and hydrous minerals, possibly associated with porphyry-style hydrothermally altered and mineralized rocks. 

Fig. 14.3. (a) Bone section under polarized light, black line outlines where Raman images were acquired. Polarized Raman images of (b) phosphate V2/amide III, (c) phosphate Vi/amide I, and (d) carbonate/phosphate V2 band ratios at the interface between osteon and interstitial bone, (e and f) Three-dimensional view of phosphate Vi/amide I ratio for different polarization directions. Reprinted with permission from [1]... 

Figure 4.17 Band ratio images of synthetic data (a) is the band ratio image spectral channels 75/25, (b) is the band ratio image at spectral channels 75/68.

A final quantitative example is that of determining the % ethylene in ethylene-propylene copolymers (EPM). The International Institute of Synthetic Rubber Producers (IIRP) Technical/Operating Committee and the American Society for Testing and Materials (ASTM) cooperated to produce an updated standard method [56]. They also produced a set of standards with the ethylene content established by 13C NMR. Those standards were utilised by Parker and Waddell to study the photoacoustic determination of % ethylene [57]. Three of the four infrared band ratios specified by ASTM were measured, 1378/1462, 1378/722, and 1156/722. The fourth one, 1156/4255, was not used since it involves measurements in the near-IR region. Baselines were drawn by the valley-to-valley technique as illustrated in Figure 2.11. 

Quantitation of PA-FTIR data appears to be generally applicable in the analysis of rubbers and polymers. The chances of success are best if the strongest, possibly saturated, infrared bands are avoided. The quality of the results are improved if band ratioing is used to compensate for experimental variables. 

Table II. Near Infrared Band Ratios Effect of Concentration ...

TABLE 2.16 The different chitin/chitosan reported IR absorption band ratios, their corresponding degree of N-acetylation ranges advantages and disadvantages... 

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