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

Damen, M. C. J.

Bibliographic data

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:: Spectral components analysis: Rationale and results. C. L. Wiegand & A. J. Richardson

Document type:: Multivolume work

Structure type:: Chapter

349 xLanted at :ions and months late lonirrigated .5 June to 15 . the corn :ion at 200 luction. conducted at k3 long. ;rtic die North )°W) on a stolls. Both Lants/ha in lurth was Ly planted ition of a i the rate of lead-sized 300 plant/ha if mepiquat and 25 g/ha and at first Lning densely the <NT) did not aintained as nations of . 1983 at the L in rows nieved two 3 197 ), and 66 m apart. s/m 2 . D) plots each Twelve hat the significant . Rainfall y 100 mm all each term in three segments of 4 x 0.6 m) tentative of corn were lite per ted in Table d frcm 1982) (Table 1) J., 1981) he 630 to 690 ! infrared igth interval. : view and was centered over >nses plus >servations r for each of luced by the ¡1). the '9) and Richardson these based on the ndville clay PVI = 0.628(RIR) - 0.778(RED) - 2.537 based on the soil line RED = -3.26 + 0.807(RIR) for the Hidalgo sandy clay loam. Photosynthetically active radiation (PAR) incident on (Io)' transmitted (T) through, reflected (R) from the composite canopy-soil backgrounds, and from the bare soil (R s ) provided the data for absorbed PAR, termed APAR, and defined as (I 0 -'P-R+R S T)/I 0 = d-T’-R'+Rs'T') (Hipps et al., 1983; Gallo et al., 1985) wherein I D = the downward PAR flux density at the top of the canopy T = the downward PAR flux density at the bottom of the canopy R = the upward PAR flux density at the top of the canopy (the PAR reflectance of the composite plant and soil background scene) Rg = the reflectance of the soil beneath the canopy, and the primes indicate that all values are normalized to I Q . For the field measurgments T, R, and Rs were measured with LI-COR ^ line quantum sensors (LI 191SB) and I Q was measured with a quantum sensor (LI 190SB). A line quantum sensor was inserted below the canopies perpendicular to the rows (wheat, cotton) and obliquely middle-to-middle (corn) for the T measurements while the sensor for measuring R frcm the canopy plus soil was inverted 30 cm above the canopies and parallel to the sensor below the canopies. The Rs term was measured by a line quantum sensor inverted 30 cm above a small area in the plots where the plants had been removed soon after emergence. The LI 190SB sensor was moved frcm plot to plot on a 2-m tall stand that was leveled at each stop. The sensor outputs for T, R, and I D and the time of the observations were all electronically logged simultaneously. Care was taken to keep all sensors level and to avoid shading the sensor measuring T by the one measuring R. The data were fit to the ccmmonly used exponential relation, ^^2 = (1-Ae“ BIAI /cosZ 2) wherein A is an arbitrary coefficient, B is the extinction coefficient, and cos Z 2 adjusts LAI for the path length through the canopy at the time of the APAR observations. At the time of each sampling, up to twto days was required to determine LAI, one day to make the PAR sensor observations, and about 1 hour to make the reflectance factor observations. Thus it was impossible to make all the necessary observations on the same day. Table 1 summarizes the dates on which the various measurements were made for each experiment. When data frcm the various sensors were merged, the sample date was considered to be that of the PAR absorption data and they were used as measured. For pairing observations, the VI and LAI data were plotted versus time and the VI and LAI estimates interpolated to the dates of the PAR measurements. The LAI samples provided information on the aboveground biomass by plant parts for those sampling dates, while yield canponents were determined on the harvest samples. Solar zenith angle was calculated frcm latitude and longitude of the experimental sites using day of year and time of day of the observations in ephimeris equations. t Equations [1 ] and [2 ] were used in analyzing the data. That is, VI and APAR data taken at different times of day were accomodated by the solar zenith angle adjustment to LAI incorporated into the terms of these equations. ■^Mention of trade names does not infer preferential treatment nor endorsement by the U.S. Department of Agriculture over similar products available frcm other sources. 6 RESULTS Data presented are paired wath the PAR observations since they were available on the fewest number of dates (Table 1). Solar zenith angles were small on all dates for corn—because measurements were made near solar noon in June and July and our latitude, 26.2°N, is close to the Tropic of Cancer—moderate for cotton, and wide-ranging for wheat. However, the solar zenith angle adjustments in LAI were made for all crops on all dates for uniformity of analysis. Expressions for each of the three terms of equation [1 ] are summarized in Table 3 for each of the three crops. Results for two vegetation indices, the normalized difference (ND) and the perpendicular vegetation index (PVI) are given as exponential, power, or linear expressions. For the first term on the left, the coefficients of determination for the dependence of LAI on PVI are 0.92 or greater for all three crops, compared with 0.77 to 0.96 when expressed in terms of ND. The results demonstrate that there is a close association between LAI and the vegetation indices as calculated from reflectance factor measurements in the visible and reflective infrared wavelengths, for all crops. f The second term on the left in equation [1 ] estimates absorbed photosynthetically active radiation (APAR) frcm leaf area indices adjusted for solar zenith angle, LAI/cosZ2* Results are presented for both the widely accepted (Charles-Edwards, 1982; Pearson, 1984) exponential form and a power expression. Again, r 2 ^ 0.93 for the exponential form and 0.89 for the power form for all crops. The extinction coefficients are 0.514, 0.540, and 0.347 for cotton, wheat, and corn, respectively. Corn had a more open canopy than the other crops and consistently transmitted more PAR at a given LAI. Pooling the observations for Aim and Nadadores cultivars of wheat may have lowered the r 2 because we found in unreported analyses that their extinction coefficients differ significantly. ■Jhe results for the right hand side of equation [1 ] in Table 3 demonstrate that APAR was estimated almost as well for cotton and corn from the vegetation indices (r 2 = 0.75 to 0.99) as frcm the LAI. For wheat, the r 2 were lower, 0.48 to 0.83. PVI gave a closer relation in every case than did ND. For wheat ND increased rapidly frcm its value of 0.2 for bare soil to 0.83 by the time LAI was 1. Consequently it was insensitive to increases in LAI beyond 1.0 where most of the APAR observations were taken and APAR was still increasing as LAI increased. In contrast, PVI increased at a diminishing rate as LAI increased. Figures 1, 2, and 3 display the data by crop for each term in equation [1']. In Figure 1 (1st term) and Figure 3 (right side term) the data are presented in terms of PVI. For all Figures the best fit curves for the equations given in Table 2 are superimposed on the data displays. The data are restricted, as in Table 2 to the dates when the data for all three variables LAI, VI, and APAR were available for pairing. The data for PVI (Figure 1) and APAR (Figure 2) are both asymptotic to the LAI axis. The result is that the APAR vs PVI data in Figure 3 appear to be nearly linear; coefficients of determination for a linear fit in Figure 3 were 0.924, 0.825, and 0.969 for cotton, wheat, and corn compared wath 0.969, .835, and .986 for the power form. Asrar, et al. (1984) reported a linear relation between APAR and the normalized difference vegetation index whereas Gallo et al. (1985) related APAR to the RIR/RED ratio, ND, and greenness (GR) vegetation indices by quadratic expressions. 7 SUMMARY The plant physiological, agroncmic, and

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