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  • 1
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    Comparison of 2.8- and 21-cm microwave radiometer observations over soils with emission model calculations (1979)
    American Geophysical Union
    Details
    Publication Date: 1979-01-01
    Print ISSN: 0148-0227
    Electronic ISSN: 2156-2202
    Topics: Geosciences
    Published by American Geophysical Union
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    PAPER CURRENT
  • 2
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    Predictions of malaria vector distribution in Belize based on multispectral satellite data (1996)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Use of multispectral satellite data to predict arthropod-borne disease trouble spots is dependent on clear understandings of environmental factors that determine the presence of disease vectors. A blind test of remote sensing-based predictions for the spatial distribution of a malaria vector, Anopheles pseudopunctipennis, was conducted as a follow-up to two years of studies on vector-environmental relationships in Belize. Four of eight sites that were predicted to be high probability locations for presence of An. pseudopunctipennis were positive and all low probability sites (0 of 12) were negative. The absence of An. pseudopunctipennis at four high probability locations probably reflects the low densities that seem to characterize field populations of this species, i.e., the population densities were below the threshold of our sampling effort. Another important malaria vector, An. darlingi, was also present at all high probability sites and absent at all low probability sites. Anopheles darlingi, like An. pseudopunctipennis, is a riverine species. Prior to these collections at ecologically defined locations, this species was last detected in Belize in 1946.
    Keywords: Life Sciences (General)
    Type: The American journal of tropical medicine and hygiene (ISSN 0002-9637); Volume 54; 3; 304-8
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    On the use of L-band multipolarization airborne SAR for surveys of crops, vineyards, and orchards in a California irrigated agricultural region (1985)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The airborne L-band synthetic aperture radar (SAR) collected multipolarization calibrated image data over an irrigated agricultural test site near Fresno, CA, on March 6, 1984. The conclusions of the study are as follows: (1) the effects of incidence angle on the measured backscattering coefficients could be removed by using a correction factor equal to the secant of the angle raised to the 1.4 power, (2) for this scene and time of year, the various polarization channels were highly correlated such that the use of more than one polarization added little to the ability of the radar to discriminate vegetation type or condition; the exception was barley which separated from vineyards only when a combination of like and cross polarization data were used (polarization was very useful for corn identification in fall crops), (3) an excellent separation between herbaceous vegetation (alfalfa, barley, and oats) or bare fields and trees in orchards existed in brightness was well correlated to alfalfa height or biomass, especially for the HH polarization combination, (5) vineyards exhibited a narrow range of brightnesses with no systematic effects of type or number of stakes nor of number of wires in the trellises nor of the size of the vines, (6) within the orchard classes, areal biomass characterized by basal area differences caused radar image brightness differences for small to medium trees but not for medium to large trees.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: NASA(JPL Aircraft SAR Workshop Proc.; p 63
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Results of remote-sensing tests for oceanography at Texas A and M University (1968)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: Airborne tests of multispectral scanners to determine usefulness of remote sensors in surveying river, coastal, and deep-sea phenomena
    Keywords: GEOPHYSICS
    Type: NASA. MANNED SPACECRAFT CENTER EARTH RESOURCES AIRCRAFT PROGRAM STATUS REV., VOL. 3 1968 (SEE N71-16166 06-13)
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    NASA TECHNICAL REPORTS
  • 5
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    Radar backscattering properties of corn and soybeans at frequencies of 1.6, 4.75, and 13.3. GHz (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The NASA Johnson Space Center made an observational study of the radar-backscattering properties of corn and soybeans in commercial fields in a test site in Webster County, IA. Aircraft-based radar scatterometers measured the backscattering coefficient of the crops at three frequencies, 1.6 GHz (L-band), 4.75 GHz (C-band), and 13.3 GHz (Ku-band), at 10 sensor look-angles (5 to 50 degrees from the nadir in steps of 5 degrees), and with several polarization combinations. Among other findings, it was determined that: (1) row direction differences among fields affected significantly the radar-backscattering coefficient of the fields when the radar system used like-polarization at look-angles from 5 to 25 degrees; (2) row-direction differences had no effect on radar backscattering when the system used either cross-polarization or look-angles greater than 25 degrees regardless of the polarization; (3) wet surface-soil moisture conditions resulted in significantly poorer spectral separability of the two crops as compared to dry-soil conditions; and (4) on the dry-soil date, the best channel for separating corn from soybeans was the C-band cross-polarized measurement at a look-angle of 50 degrees.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: (ISSN 0196-2892)
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    NASA TECHNICAL REPORTS
  • 6
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    Active Microwave Properties of Vegetation Canopies (1985)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Potential users of radar imagery need a better fundamental understanding of the capabilities of radar systems for vegetation studies than past studies provide. One approach is the use of theoretical models to predict observable active microwave properties of vegetation. This in turn requires accurate observations of backscattering coefficients and other active microwave properties in field research studies. The background document for the SRAEC program emphasizes the need to relate electromagnetic parameters to classical biophysical descriptors and to understand the role of polarization, especially cross-polarization. The broad goal of this study is to increase the understanding of the effects of canopy structure on the active microwave properties of vegetation canopies, with particular attention to polarization.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: NASA. Goddard Space Flight Center Fundamental Remote Sensing Sci. Res. Program; p 148-153
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    Effects of Vegetation Canopy Structure on Microwave Scattering (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-27
    Description: The role of canopy structure on microwave backscattering is studied. Structure refers to the size, orientation, and vertical placement of scatterers in the canopy. Models to predict the backscattering coefficient, SIGMAO, of vegetation with explicit biophysical and explicit polarization-dependent parameters were developed. Preparation for field measurements with radar scatterometers was completed. Technical progress included: (1) the modification of the Attema and Ulaby (1977) model and its multilayer variation by Hoekman et al. (1983) to include polarization explicitly (i.e., to allow for separate backscattering cross sections, SIGMA, and extinction cross sections, Q, for each polarization), (2) the investigation of the modified model to isolate canopy element orientation parameters by the rationing of SIGMAO measurements for different polarization combinations, (3) the development of expressions for bistatic scattering and canopy-substrate scattering to supplement the models, (4) the performance of sensitivity analyses on these models, (5) the modification of the Attema and Ulaby model to alloy for changes, (6) the use of the modified model with a seasonal corn data set from Kansas (Eger et al., 1983), and (7) the initiation of preparations for empirical measurements with radar spectrometer and the Mobile Radar Scatterometer in irrigated cropland to test the models.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA Goddard Space Flight Center Fundamental Remote Sensing Sci. Res. Program, Part 1; p 42
    Format: text
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    NASA TECHNICAL REPORTS
  • 8
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    Comparison of 2.8- and 21-cm microwave radiometer observations over soils with emission model calculations (1979)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: An airborne experiment was conducted under NASA auspices to test the feasibility of detecting soil moisture by microwave remote sensing techniques over agricultural fields near Phoenix, Arizona at midday of April 5, 1974 and at dawn of the following day. Extensive ground data were obtained from 96 bare, sixteen hectare fields. Observations made using a scanning (2.8 cm) and a nonscanning (21 cm) radiometer were compared with the predictions of a radiative transfer emission model. It is shown that (1) the emitted intensity at both wavelengths correlates best with the near surface moisture, (2) surface roughness is found to more strongly affect the degree of polarization than the emitted intensity, (3) the slope of the intensity-moisture curves decreases in going from day to dawn, and (4) increased near surface moisture at dawn is characterized by increased polarization of emissions. The results of the experiment indicate that microwave techniques can be used to observe the history of the near surface moisture. The subsurface history must be inferred from soil physics models which use microwave results as boundary conditions.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Journal of Geophysical Research; 84; Jan. 20
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    NASA TECHNICAL REPORTS
  • 9
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    Crop identification with multifrequency, multipolarization, and multiangle radars (1982)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: In a corn and soybeans test site in Webster County, Iowa, airborne radar scatterometers were used on August 19 and September 10, 1980, to investigate the backscattering properties of these crops at wavelengths of 2.3, 6.3, and 19 cm (Ku-, C-, and L-band, respectively). Both horizontal transmit-horizontal receiver (HH) polarization and horizontal transmit-vertical receive (HV) polarization combinations were used at L- and C-band. Only the VV polarization combination was available at Ku-band. Measurements were obtained at 10 angles of observation from 5 to 50 deg in steps of 5 deg (referenced to the nadir). Excellent separation between corn and soybeans was achieved when either C-band HV at 50 deg or when a defined depolarization factor was used at C-band. Good separation existed at L-band also using either L-band HH at 50 deg or an L-band polarization factor. Significant row direction effects were observed for all HH data near 10 deg. Significant effects of surface soil moisture were observed for all configurations at L-band and C-band.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
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    NASA TECHNICAL REPORTS
  • 10
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    Development and evaluation of techniques for using combined microwave and optical image data for vegetation studies (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Techniques for using combined image data from the Shuttle Imaging Radar (SIR-B) and the LANDSAT Thematic Mapper (TM) or Multispectral Scanner (MSS) for studies of irrigated crops, and boreal and deciduous forests are developed and evaluated. The effects of the structure and composition of crop canopies and soil surfaces on multiangle L-band HH (Horizontal polarization for transmission and reception) backscattering and on optical reflectance (in TM or MSS bands viewed at the nadir) are investigated. The relative accuracy of digital, calibrated SIR-B image data and LANDSAT TM or MSS image data is evaluated. Textural information extraction-techniques are developed for radar and optical image analysis.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: JPL The SIR-B Sci. Invest. Plan; 3 p
    Format: text
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    NASA TECHNICAL REPORTS
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