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Silva, L. F.

Publications and source records attributed to Silva, L. F..

33 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Electrical methods of determining soil moisture content

The electrical permittivity of soils is a useful indicator of soil moisture content. Two methods of determining the permittivity profile in soils are examined. A method due to Becher is found to be inapplicable to this situation. A method of Slichter, however, appears to be feasible. The results of Slichter's method are extended to the proposal of an instrument design that could measure available soil moisture profile (percent available soil moisture as a function of depth) from a surface measurement to an expected resolution of 10 to 20 cm.

Silva, L. F.↗
NASA NTRS1975

Machine aided multispectral analysis utilizing Skylab thermal data for land use mapping

Skylab eight channel multispectral scanner data obtained in January 1974, was used for land-use analysis of Allen County, Indiana. The data-set which includes one visible channel, four near infrared channels, two middle infrared channels, and one far infrared channel was from the X-5 detector array of the S-192 experiment in the Earth Resources Experiment Package on board Skylab. The results indicate that a good-quality far infrared (thermal) channel is very valuable for land use mapping during the winter months.

Biehl, L. L.↗
NASA NTRS1974

Analysis of Skylab MSS data, and calibration of thermal data over Lake Monroe, Indiana

The author has identified the following significant results. The SL/4-S192 data over northern Indiana looks good. The thermal band looks very encouraging. The preliminary analysis indicates so far that it will be difficult to distinguish some land use classes because of the lack of vegetation. Preliminary analysis of the thermal band in particular indicates that there appears to be a correlation of the hot spots in the data over the Ft. Wayne, Indiana area and its industrial centers.

Silva, L. F.↗
NASA NTRS1974

Evaluation of Skylab data for land use mapping

The present work compares four multispectral data sets acquired within a 24-hour time period over an area in south-central Indiana in a land use analysis of the study area. Data sets were acquired by the 4-channel multispectral scanner (MSS) on the ERTS satellite, the Earth Resource Environmental Package (EREP) 13-channel MSS on Skylab, the color infrared photography from the EREP camera system, and the black and white multiband photography from the EREP camera system. Overall performance of MSS data sets was better than that of digitized photographic data sets. Digitized color IR data sets were better overall than digitized black and white sets. Also, overall performance of 'optimum' four channels in Skylab MSS data set was essentially the same as that for the ERTS MSS data sets. However, when the four channels in the Skylab MSS which most nearly correspond to those in the ERTS MSS were used, overall performance of Skylab MSS data set was significantly lower than that for the ERTS MSS.

Biehl, L. L.↗
NASA NTRS1973

Emission and reflection from healthy and stressed natural targets with computer analysis of spectroradiometric and multispectral scanner data

Special emphasis was on corn plants, and the healthy targets were differentiated from stressed ones by remote sensing. Infrared radiometry of plants is reviewed thoroughly with emphasis on agricultural crops. Theory and error analysis of the determination of emittance of a natural target by radiometer is discussed. Experiments were conducted on corn (Zea mays L.) plants with long wavelength spectroradiometer under field conditions. Analysis of multispectral scanner data of ten selected flightlines of Corn Blight Watch Experiment of 1972 indicated: (1) There was no regular pattern of the mean response of the higher level/levels blighted corn vs. lower level/levels blighted corn in any of the spectral channels. (2) The greater the difference between the blight levels, the more statistically separable they usually were in subsets of one, two, three and four spectral channels.

Kumar, R.↗
NASA NTRS1973

A spectroradiometer for field use.

Description of a spectroradiometer system that measures the intensity of incident and reflected radiation from 0.37 to 2.52 microns and emitted radiation from 2.76 to 13.88 microns. The system is designed to operate in an outdoor environment. Provisions exist for photographic annotation of field data setups.

Leamer, R. W.↗
NASA NTRS1973

Light ray tracing through a leaf cross section

A light ray, incident at about 5 deg to the normal, is geometrically plotted through the drawing of the cross section of a soybean leaf using Fresnel's equations and Snell's law. The optical mediums of the leaf considered for ray tracing are: air, cell sap, chloroplast, and cell wall. The ray is also drawn through the same leaf cross section with cell wall and air as the only optical mediums. The values of the reflection and transmission found from the ray tracing tests agree closely with the experimental results obtained using a Beckman Dk-2A Spectroreflector.

Kumar, R.↗
NASA NTRS1972

Measurements program in remote sensing at Purdue University

The measurements program has been concerned with five basic research areas during 1971. These areas are: (1) The influence of haze layers upon remotely sensed surface properties; (2) electrical methods of soil moisture measurement; (3) thermographic studies of vegetation under nutritional stress; (4) improved field spectroradiometry; and (5) biological spectropho-tometry. All of these projects have risen out of problems generated from the overall laboratory mission. The emphasis in this paper is on instrumentation and techniques.

Silva, L. F.↗