Remote sensing for resources development and environmental management: Remote sensing for resources development and environmental management

Damen, M. C. J.

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Multivolume work

Persistent identifier:: 856342815

Title:: Remote sensing for resources development and environmental management

Sub title:: proceedings of the 7th international Symposium, Enschede, 25 - 29 August 1986

Year of publication:: 1986

Place of publication:: Rotterdam; Boston

Publisher of the original:: A. A. Balkema

Identifier (digital):: 856342815

Language:: English

Additional Notes:: Volume 1-3 erschienen von 1986-1988

Editor:: Damen, M. C. J.

Document type:: Multivolume work

Volume

Persistent identifier:: 856343064

Title:: Remote sensing for resources development and environmental management

Sub title:: proceedings of the 7th international Symposium, Enschede, 25 - 29 August 1986

Scope:: XV, 547 Seiten

Year of publication:: 1986

Place of publication:: Rotterdam; Boston

Publisher of the original:: A. A. Balkema

Identifier (digital):: 856343064

Illustration:: Illustrationen, Diagramme

Signature of the source:: ZS 312(26,7,1)

Language:: English

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Editor:: Damen, M. C. J.

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2016

Document type:: Volume

Collection:: Earth sciences

Chapter

Title:: 3 Spectral signatures of objects. Chairman: G. Guyot, Liaison: N. J. J. Bunnik

Document type:: Multivolume work

Structure type:: Chapter

Chapter

Title:: Theoretic reflection modelling of soil surface properties. B. P. J. van den Bergh & B. A. M. Bouman

Document type:: Multivolume work

Structure type:: Chapter

332 The second hypothesis, whereby k is independent on par ticle size, seems to be justified only in cases where the particle size is greater than the wavelength of incident radiation (Kortum, 1969). However, for most soils in natural condition, small particles tend to cluster in aggregates. Thus, in case of clayey samples particle size should be interpreted as the smallest existing aggregate size. The samples used by B&H were aggregates of clay particles and several times larger in diameter than the wavelength of incident radiation. Plots were made of Ln(r) versus wavelength for samples of different aggregate size and of Ln(r) versus aggre gate diameter at different wavelengths (Bouman, 1986). Interpretation of these plots led to the following formula, equating mean penetrated layer thickness d to wavelength X and aggregate diameter 0 : d = \T£*Ln(0/X) (in ) eq.3 This equation was tested on the .(B&H) measured reflec tance values of the kaolinite and bentonite clay samples. To this end, the coefficients of absorption of the clay minerals were calculated as a function of wavelength, using two samples of different aggre gate size. With the aid of the values calculated for k, reflectance r was computed for the other aggregate sizes and compared with the measured values, see figu re 1. Figure 1. Calculated and measured reflectance values for kaolinite (o) and bentonite (x) clay samples, (measured values are from Bowers and Hanks, 1965) On the whole, there seems to be a great consistence between measured reflectance and reflectance computed using equation 3. Any decrease in reflectance with increasing particle size is fairly well predicted. The total mean deviation computed for the kaolinite and the bentonite samples is 3.5 % resp. 3.9 % (n = 70). Boundary conditions for the validity of equation 3 could not be established for lack of data in literatu re. It should be clear however, that particles or aggregates infinitely small or very large are beyond the limits of this formula. In figure 1 it can be seen that for large values of 0, reflectance r tends to become overestimated. There appears to be a maximal particle/aggregate size beyond which reflectance is no longer significantly reduced (Belonogova, 1959; Stoner and Baumgardner, 1980). The influence of mineralogy It is assumed that the effect of different mineral composition on reflection can be described by means of a weighed average of the coefficients of absorption of the individual components. The coefficients of weight are based on the percentages of volume of each component. For a homogeneous mixture of minerals, the coefficient of absorption k^ is proposed to be : k = y*c. k. (m 2 ) eq.4 s 1 1 in which : k = coefficient of absorption of the mi neral mixture k. = coefficient of absorption of mineral i c^ = percentage of volume of mineral i In 1970, Hunt and Salisbury published the results of extensive reflectance measurements of samples of pure minerals of various particle sizes. With the aid of equation 3, the coefficients of absorption of three minerals quartz, gypsum and calcite, have been calcu lated as a function of wavelength of incident radia tion, see table 1. Table 1. Coefficient of absorption k as a function of wavelength of incident radiation for quartz, gypsum and calcite. Wavelength (^i) Coeff. of absorption (-1 ^ 2 ) Quartz Gypsum Calcite 0.4 i. 086 1, . 205 1 . . 188 0.6 0 . 983 1, . 062 1 . ,062 O CO 0 . 903 o, . 974 0 . ,969 1.0 0 . 851 o, . 899 0 . , 905 1 . 2 0 . 808 0 .839 0 . ,855 1 . 4 0 . 775 o, .777 0 . ,82 1 1.6 0 . 748 o, .739 0 . ,793 1.8 0. 72 1 o, .7 19 0 . .771 o C\1 0 . 705 0 . 557 0 . .741 2 . 2 0 . 689 0 . 565 0 . , 724 2.4 o . 675 0 .451 0 . , 688 For any dry mixtu re of th ese m ine r a 1 s in a well so r ted parti ele s iz e c las S / r e f 1 e ctance r can n ow be calc ulate d w ith the aid o f equa- tion 3 and 4 . Table 2 summariz es the m inera- logical prop er ti e s and me an pa rti cle s ize of two sam pies from ' Tunes ian soil su r f ace s (van den Ber gh, 1 986) . The samples hav e bee n air- dried i n ord er to pres e rv e the ca leite and gypsum conte nt an d wer e placed in smal 1 cups with a depth of about 20 mm . Table 2 . Min ¡éralo gical pr opert ies and mean partic1 e s i z e of two T une ■ s ian soi 1 s am ¡pies . Property S amp 1 e A Sample B quartz (%) 85 70 gypsum (%) 5 25 calcite (%) 10 5 organic matt er ( % ) 0 . 5 0 . 2 mean pa rtic 1 e siz e 75 -12 5 1 2 5-250 (yim) Sample ref le ctanc es we re both cal culat ed and measure d with the NIWARS- spect rof otome ter ; results are given in f igu res 2 a a nd 2b I 100 .. '-'80 .. Figur« of sac 60 50 iiR 40 § 30 1 20 I I <D u 10 Figur« of sari In gei the me reflec B is c dips c reflec pronoi ted r< tanc e bratic ces ii Hunt i and tc struct and S< sample The ii The ii from < many t dry sc sorpt; on it: which attemj water the ii ferenc 1965)

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