Proceedings of the Symposium on Global and Environmental Monitoring: Proceedings of the Symposium on Global and Environmental Monitoring

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Persistent identifier:: 856665355

Title:: Proceedings of the Symposium on Global and Environmental Monitoring

Sub title:: techniques and impacts ; September 17 - 21, 1990, Victoria Conference Centre, Victoria, British Columbia, Canada

Year of publication:: 1990

Place of publication:: Victoria, BC

Publisher of the original:: [Verlag nicht ermittelbar]

Identifier (digital):: 856665355

Language:: English

Document type:: Multivolume work

Volume

Persistent identifier:: 856669164

Title:: Proceedings of the Symposium on Global and Environmental Monitoring

Sub title:: techniques and impacts; September 17 - 21, 1990, Victoria Conference Centre, Victoria, British Columbia, Canada

Scope:: XIV, 912 Seiten

Year of publication:: 1990

Place of publication:: Victoria, BC

Publisher of the original:: [Verlag nicht ermittelbar]

Identifier (digital):: 856669164

Illustration:: Illustrationen, Diagramme, Karten

Signature of the source:: ZS 312(28,7,1)

Language:: English

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

Editor:: International Society for Photogrammetry and Remote Sensing, Commission of Photographic and Remote Sensing Data

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:: [TP-4 SOILS]

Document type:: Multivolume work

Structure type:: Chapter

Chapter

Title:: REFLECTANCE IN SPOT BANDS AND MICROWAVE BACKSCATTERING COEFFICIENT IN C BAND AS A FUNCTION OF STAGE OF SLAKING OF BARE SOIL. Patrick BERTUZZI,Dominique COURAULT, Gérard GUYOT and Emile CHAPUIS

Document type:: Multivolume work

Structure type:: Chapter

2. DATA COLLECTION 2.1 Location and Site Description The experiments were conducted at the Soil Science Laboratory of the Institut National de la Recherche Agronomique (I.N.R.A.) of Montfavet (France) during July 1988. The soil was a clay loam with about 27 % of clay and 62 % of silt. The field (0.1 ha) was initially tilled with a rotary digging machine. Soil clods were arranged in an apparently random manner and resulted from soil break up tillage implements (no tools marks or tillage directions). The general soil surface was flat. Rainfall was simulated using a sprinkler irrigation equipment composed of an aluminium frame (20 m long) with regularly distributed sprinklers and supported by two pneumatic tyred wheels on each side. The irrigation system was moved across the experimental field on two tramlines located on each side of the field. Rainfall was applied during 4 successive periods to simulate five stages of slaking (including the initial stage). The rainfall intensity was approximately 40 mmh' 1 . The cumulative rainfall precipitation was measured. At each stage of slaking, ground observations concurrent with remote sensing measurements were performed on the experimental field under wet and dry surface soil moisture conditions. Wet condition is obtained after completely surface draining (no puddles). Dry condition is reached by natural evaporation during two or three days. 2.2 Remote sensed data. Table 1 : Spectral band of the SPOT simulation radiometer. Band Wavelength (nm) XS1 500 - 590 (a) XS2 600 - 690 (b) XS3 790 - 900 (c) (a) green band (b) red band (c) near infrared band This instrument has two heads, (l)the first is equipped with diffusing screens and measures irradiance. It was fixed at the bottom of the crane. (2)the second is equipped with a 12° field of view and measures field target radiance. It was fixed at the mobile platform. The plot position, in respect to viewing and illumination directions are seen in Figure 2. The radiometer is enable to simulate SPOT sattelite data taken in nadir viewing angle (0* from nadir) and oblique viewing angle, here 23° (from to nadir). The choosen angle of incidence was different but quite near the oblique viewing angle of the SPOT satellite (27‘ relative to nadir). One cloud free day, thirty radiometric measurements in the three spectral bands were recorded during the travel of the platform and averaged. Radiometric measurements were performed at three approximately constant solar illumination angle at 6.00 am, 12.00 and 6.00 pm G.M.T. The two instruments were mounted an a mobile platform of a crane-boom. They were at about 19.70 m height above the soil surface. Remote sensing measurements were performed on about one third of the experimental field (Figure 1). 2.2.1 Microwave measurements. We used the scatterometer RAMSES designed by the Centre National d'Etudes Spatiales (C.N.E.S.) of Toulouse (France). It is a frequency-modulated continuous wave, multifrequency and multipolarization system. Microwave measurements were made at 5 3 GHz (C band) and HH polarization. According to theoretical and experimental results (Ulaby et al., 1978; Ulaby et al., 1982), we used only small or large angles of incidence to increase the sensitivity of microwave measurements to roughness changes. The two angles of incidence were fixed at 0‘ (nadir j and 50' from nadir. The surface foot print varied from 3 m 2 at nadir to 15 m 2 at 50*. Microwave measurements were expressed in term of the backscattermg coefficient (<r°) and reported in units of decibels. Spatial averaging of the <r° measurements was achieved by recording 200 <r° values during the travel of the platform along the crane-boom. 2.2.2 Optical measurements. They were performed in three different spectral bands (Table 1.) using a SPOT simulation radiometer (Guyot et al, 1984). 2.3 Ground measurements Depending on soil moisture conditions, ground observations of soil moisture, soil roughness and determination of stage of slaking were performed on the the field area not seen by the intruments (Figure 1). Ten gravimetric water content samples were collected approximately at the same location to measure soil moisture (Figure 1). They were taken from 0 to 2 cm depth. Dry bulk densities were measured at 3 cm depth using a gamma transmission probe (Bertuzzi et al., 1987). They were extrapolated at the 0-2 cm soil layer to compute volumetric water contents by combining gravimetric water contents and dry bulk densities. An automated non-contact Laser profile meter was used to measure changes in soil surface roughness (Bertuzzi et al., 1990a). Each profile was 2 m long with 1000 elevation data recorded at 2 mm sampling interval. The accuracy on elevation data was less than 0.25 mm. After each rainfall, twelve profiles, regularly distributed on the experimental field were recorded always at the same location (Figure 1). Six profiles were recorded in the main longitudinal eastern -» western direction of the field, parallel to the tillage direction. The six other profiles were recorded in the nothern -> southern direction perpendicular to the tillage direction. At each stage of slaking, roughness profiles were used to compute two roughness indices. The first one is the most common standard deviation of height (s). The

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