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  • COMMUNICATIONS AND RADAR  (2)
  • EARTH RESOURCES AND REMOTE SENSING  (2)
  • Organic Chemistry
  • 1990-1994  (4)
  • 1935-1939
  • 1992  (4)
  • 1
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    Identification of a far-red reflectance response to ectomycorrhizae in slash pine (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Spectral reflectances were measured for the canopies of Pinus elliottii seedlings that were inoculated versus noninoculated with the ectomycorrhizal fungus Pisolithus tinctorius. Reflectances of the less vigorous, noninoculated seedlings increased substantially at visible and near-IR wavelengths compared to the more vigorous, inoculated seedlings. An algorithm was developed to indicate the spectral regions in which reflectance was most sensitive to ectomycorrhizae. The reflectance curve of the more vigorous seedlings was used as a standard of comparison. The spectral regions defined by this algorithm are denoted as regions of maximum reflectance sensitivity. Far-red and near-IR photography filtered to the region of maximum sensitivity (700 nm) were used to enable visualization of a 'blue shift' reflectance response to decreased vigor in the noninoculated seedlings in response to these differences of mycorrhizal development.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Journal of Remote Sensing (ISSN 0143-1161); 13; 925-932
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Response of Thematic Mapper bands to plant water stress (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Changes in leaf reflectance as water content decreases have been hypothesized to occur in the 1.55-1.75 and 2.08-2.35 micron wavelength regions. To evaluate this hypothesis, studies were conducted on ryegrass (Lolium multiflorum Lam.) and oats (Avena sativa L.), which were grown in a controlled, outdoor situation. Both fully-watered control beds and water-stressed beds were periodically examined with a spectroradiometer calibrated against a reflectance reference of polytetrafluoroethylene. The observed changes correspond to those predicted by stochastic leaf models employed by other investigators (leaf reflection increases in the 1.55-1.75 micron region as leaf water content decreases). Although the percentage changes in TM bands 1-3 are nearly as great as those found in TM bands 5 and 7, the absolute values of reflectance change are much lower. It is believed that these patterns are probably characteristic of a broad range of vegetation types. In terms of phenomena detection, these patterns should be considered in any practical remote sensing sensor scenario.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Journal of Remote Sensing (ISSN 0143-1161); 13; 10, J
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    An optimal GPS data processing technique (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: A formula is derived to optimally combine dual-frequency GPS (Global Positioning System) pseudorange and carrier phase data streams into a single equivalent data stream, reducing the data volume and computing time in the filtering process for parameter estimation by a factor of four. The resulting single data stream is that of carrier phase measurements with both data noise and bias uncertainty strictly defined. With this analytical formula the single stream of equivalent GPS measurements can be efficiently formed by simple numerical calculations without any degradation in data strength. The formulation for the optimally combined GPS data and their covariances are given in closed form. Carrier phase ambiguity resolution, when feasible, is improved due to the preservation of the full data strength with the optimal data combining process.
    Keywords: COMMUNICATIONS AND RADAR
    Type: In: IEEE PLANS '92 - Position Location and Navigation Symposium, Monterey, CA, Mar. 24-27, 1992, Record (A93-10976 01-04); p. 21-26.
    Format: text
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  • 4
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    L- and K-band LMSS propagation measurements using MARECS-B, OLYMPUS, and ACTS (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: L-band measurements of land mobile satellite systems (LMSS) propagation effects were last made at the end of 1988, but some voids were left in the database, making modeling of low elevation roadside tree shadowing and multipath reflections difficult for some path geometries. Transmission of a pilot tone from MARECS-B at 55 deg West during Sep. and Dec. 1991 gave an opportunity to fill the gaps in the experimental results. Two campaigns during which fade data were obtained at elevation angles from 7 deg to 40 deg are described. Below 15 deg, specular terrain reflections in a non-shadowing, hilly environment were observed to introduce significant fading. Although the reflecting surface was at a distance of up to several km, it is shown that the reflected signals are delayed by less than 1 microsec. Mobile measurements were also attempted receiving the 20 GHz Olympus beacon, but antenna pointing problems restricted first results to straight-line driving.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL, Proceedings of the 16th NASA Propagation Experimenters Meeting (NAPEX 16) and the Advanced Communications Technology Satellite (ACTS) Propagation Studies Miniworkshop p 27-33 (SEE N93-26463 09-32; JPL, Proceedings of
    Format: application/pdf
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