Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Histogram”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

The surface albedo of the earth in the near ultraviolet /330-340 nm/

Satellite-borne measurements of solar radiation backscattered by the earth and atmosphere allow a determination of the surface albedo in the near ultraviolet. The data yielded albedos at tropical latitudes during a 15-month period in 1979-1980. The wavelengths studied are 331.2 and 339.8 nm. Sixty-nine percent of the measurements imply albedos less than 0.3. Higher values include a contribution due to reflection from clouds and are consistent with previous estimates of the fractional cloudover in the tropics. An albedo histogram based on a bin width of 0.1 shows results in the range 0.1-0.2 to be the most frequent, appearing in 29% of the cases, although values which span the entire range 0.0-1.0 are present. The derived albedos show no correlation with solar zenith angle. This result is consistent with the fact that, at the wavelengths considered, the diffuse integrated intensity is larger than the attenuated direct solar beam near the ground.

Frederick, J. E.↗
NASA NTRS1981

Results from the central Hyades survey

Results of a soft X-ray survey of the central 5 deg of the Hyades star cluster made with the Einstein Observatory Imaging Proportional Counter are presented. Virtually all of the late F and early G stars in the cluster were detected at an X-ray luminosity of greater than 10 to the 28.5 erg/sec, although only about 50% of the stars in the cluster as a whole were detected. Plots of X-ray luminosity against B-V index indicate that the typical solar-type star in the Hyades is emitting soft X-rays at a level approximately 30 times that of the active sun. Histograms of the X-ray to bolometric luminosity ratio reveal a gradual distinction between late A-early F stars, which are expected to possess little or no convective envelope, and solar-type (F8-G5) stars, with convective outer atmospheres. Results confirm the dependence of stellar coronal activity on rotation, and establish the prevalence of stellar coronae throughout the main sequence and the giant regions of the H-R diagram.

Stern, R. A.↗
NASA NTRS1981

A statistical analysis of simulated data from potential stratospheric satellite missions

A simplified one-dimensional model is used to analyze simulated data from typical proposed satellite measurements of trace species in the stratosphere. Uncertainties are introduced in simulated species concentration measurements and applied to the basic physical and chemical model data. The results of the calculations are then used to predict uncertainties in the species concentrations computed by the model. Candidate satellite missions can be evaluated for net information acquired by applying the error analysis. An abbreviated depiction of the computational procedure is given, and sample histograms based on an accumulation of 200 calculations are shown for H2O2 and ClNO3, demonstrating that emergent species distributions are roughly Gaussian in the logarithm of number density. Calculated vertical concentration profiles for these two species are presented.

Nealy, J. E.↗
NASA NTRS1984

Ditigal-Image Enhancement

Programable system enhances digitally monocular and stereographic images at video rates. Provides automatic and interactive enhancement modes based on histogram modification and intensity-mapping techniques.

Woods, R.↗
NASA NTRS1982

Image segmentation survey

The methodologies and capabilities of image segmentation techniques are reviewed. Single linkage schemes, hybrid linkage schemes, centroid linkage schemes, histogram mode seeking, spatial clustering, and split and merge schemes are addressed.

Haralick, R. M.↗
NASA NTRS1983

Study on radiometric consistency of LANDSAT-4 multispectral scanner

Two full frames of radiometrically corrected LANDSAT-4 MSS data were examined to determine a number of radiometric properties. It was found that LANDSAT-4 MSS produces data of good quality with dynamic ranges and target responses qualitatively similar to those of previous MSS sensors. Banding appears to be quite well corrected, with a residual rms error of about 0.3 digital counts being measured; the histogram equalization algorithm appears to be working as advertised. A low level coherent noise effect was found in all bands, appearing in uniform areas as a diagonal striping pattern. The principle component of this noise was found by Fourier analysis to be a highly consistent wavelength of 3.6 pixels along a scan line (28 KHz). The magnitude of this effect ranged from about 0.75 of one count in the worst band (Band 1) to only about 0.25 counts in the best band (Band 4). Preparations were made for establishing a relative radiometric calibration from MSS 4 data with respect to MSS 3.

Malila, W. A.↗
NASA NTRS1983

Analysis of multispectral data using an unsupervised classification technique: Application to VAS

A statistical classification method based on clustering of multidimensional histograms was applied to several channels of the VAS multispectral imagery. The method automatically discriminates and classifies atmospheric ground features such as cloud types, atmospheric moisture patterns, ocean, or ground. Such a clustering method has the advantage of forming natural data groupings, without a priori classification. Clusters are not limited by straight lines or plane surfaces as is the case in threshold methods. The method was applied to simultaneous full resolution images from channels 8 (11.2 micron), 10 (6.7 micron), and 12 (3.9 micron). Twenty image segments of 64 by 64, 12 image segments of 128 by 128, and 4 image segments of 254 by 254 picture elements were analyzed. In addition, normal VISSR mode images at 1800, 1830, and 2000 GMT were used to identify the classes. The gray levels measured along a scan line and the result of the classification scheme (dashed curves) for the three channels investigated are shown. Each point of the image is affected to a class. Each class is identified by a center of gravity that is represented by a vector in the three dimensional space of gray levels.

Szejwach, G.↗
NASA NTRS1983

TM report

Key spectral, radiometric, and geometric characteristics of the TM sensor are examined. Spectrally, band 5 is slightly wider than specified and its upper edge at 50% of miximum of 1784 nm includes some unintended overlap with water absorption bands. Thermal band 6 is half the expected width. Radiometrically, the TM has extreme linearity and stability in comparison with previous MSS photomultiplier systems. Forward and reverse scans on TM show some unexplained radiometric differences of up to four digital levels. Primary focal plane bands show a monotomic decrease in gain of about 5% in the five months since launch. The relative internal gains of bands 5 and 7 varied with a period of about 60 days and an amplitude of about 6%. Radiometric calibration must be applied before histogram equalization algorithms to preserve radiometric accuracy. Geometrically, channel 4 in band 2 has a smaller modulation transfer function than desired. There is apparent misregistration of .75 pixels along scan and 0.2 pixels across scan.

Barker, J. L.↗
NASA NTRS1983

Thermal band characterization of LANDSAT-4 thematic mapper

The TM band 6 shutter background and the 34.7 C internal black body signal were measured over 50 day dates. Variability of the shutter background temperature was from 7 C to 11 C. For ten specific images, the digital counts of the calibration data were measured. The average pulse value of the black body peak decreased from 174 to 149 counts while the shutter background counts varied as a function of shutter temperature from 77 to 85. Relative internal gains between the four channels were calculated and compared to prelaunch values. They showed gains over 9 months of up to 5%. Frequency histograms of number of pixels vs. digital counts from a night scene were used to determine gain relative to the mean and to discern a systematic along-scan pattern in a difference between forward and reverse scan counts of up to 0.5. A corrected digital image was obtained. A temperature estimate for and area of Lake Erie of 18.5 C to 19.9 C was obtained. Local temperature records showed 21 C.

Lansing, J. C.↗
NASA NTRS1983

Evaluation of the radiometric quality of the TM data using clustering and multispectral distance measures

Radiometrically and geometrically corrected TM data from three different geographic locations were examined. Histograms were inspected for each band to determine the dynamic range of the data, the shape of the distributions, and to verify whether empty bins were introduced by the radiometric correction process. The effect of geometric correction on the radiometry of the resampled pixels was determined. The information content between TM and MSS data sets were compared and the TM data were used to map the thermal effluent discharge into a river ecosystem from a nuclear thermal power plant, and application only possible previously only possible through the acquisition of thermal infrared scanner data from aircraft altitudes.

Bartolucci, L. A.↗
NASA NTRS1981

MSU Test of P-model

Results of running key station data (soil, air, and dew point temperatures, net irradiation, and wind direction and speed) from Michigan through the P-model are presented. The details of each of the 55 error calculations are shown in tables. A histogram is included showing errors in degrees Fahrenheit.

Source record↗
NASA NTRS1981

The magnifying glass - A feature space local expansion for visual analysis

The Magnifying Glass Transformation (MGT) technique is proposed, as a multichannel spectral operation yielding visual imagery which is enhanced in a specified spectral vicinity, guided by the statistics of training samples. An application example is that in which the discrimination among spectral neighbors within an interactive display may be increased without altering distant object appearances or overall interpretation. A direct histogram specification technique is applied to the channels within the multispectral image so that a subset of the spectral domain occupies an increased fraction of the domain. The transformation is carried out by obtaining the training information, establishing the condition of the covariance matrix, determining the influenced solid, and initializing the lookup table. Finally, the image is transformed.

Juday, R. D.↗
NASA NTRS1982

Lunar regolith - Petrology of the less than 10 micron fraction

Petrographic data for the less than 10 micron fraction from four lunar surface soils are presented in an attempt to characterize the modal mineralogy of this fraction. Individual grains were studied with a scanning/transmission electron microscope with an attached energy dispersive spectrometer. Energy dispersive analytical data are presented, and comparative modal petrology of the soils is shown. Also presented are grain size histograms and diagrammatic representation of comparative modal data for the soils, as well as the feldspathic glass/mafic glass ratio, plagioclase/mafic mineral ratio, and SiO2 modal percent for different size fractions of the four types of soil. The modal results are consistent with chemical data regarding feldspathic and KREEP enrichment in the finest fraction. Grain-size distributions are inconsistent with a fine-grained exotic component derived from distant sources.

Devine, J. M.↗
NASA NTRS1982

Design and calibration of a coherent lidar for measurement of atmospheric backscatter

This paper discusses the background requirements for, and the design and calibration of a coherent Doppler lidar which is oriented specifically toward the measurement of low values of atmospheric backscatter at a wavelength of 10.6 microns. The lidar is a compact, continuous wave system which can operate in two modes, multiple particle scattering and single particle scattering. In the multiple scattering mode, the lidar employs an extended focal volume and utilizes a technique similar to Dicke switching to achieve measurement of the volume backscatter. In the single scattering mode, the focal volume is reduced to ensure a high probability of single particle scattering. Measurement of the single particle backscatter as a function of time leads to the formation of signal histogram from which the volume backscatter can be inferred. In addition to providing the atmospheric backscatter value, appropriate data processing algorithms and focal volume calibration allow the single particle mode to yield information on the atmospheric aerosol scattering cross-section distribution.

Jones, W. D.↗
NASA NTRS1983

Cosmic-ray abundances of Sn, Te, Xe, and Ba nuclei measured on HEAO 3

The results of an analysis of HEAO 3 Heavy Nuclei Experimental data covering 440 days of observations of Sn-Ba nuclei in cosmic rays are reported. The particles were detected by a Cernkov counter, and a Z-squared ceiling was calculated to normalize the histograms produced. The observed large abundance of Sn and Ba relative to other elements in the region of interest indicated a predominance of the s-process in the source of the particles. When account was taken of first ionization potential effects, the data indicated that the material could be solar system in origin. A source dominated by the r-process nucleosynthesis was ruled out at the 0.93 confidence level.

Binns, W. R.↗
NASA NTRS1982

A statistical model for radar images of agricultural scenes

The presently derived and validated statistical model for radar images containing many different homogeneous fields predicts the probability density functions of radar images of entire agricultural scenes, thereby allowing histograms of large scenes composed of a variety of crops to be described. Seasat-A SAR images of agricultural scenes are accurately predicted by the model on the basis of three assumptions: each field has the same SNR, all target classes cover approximately the same area, and the true reflectivity characterizing each individual target class is a uniformly distributed random variable. The model is expected to be useful in the design of data processing algorithms and for scene analysis using radar images.

Frost, V. S.↗
NASA NTRS1983

Some constraints on the color-magnitude diagram of giants in the galactic spheroid

The color-magnitude diagram of giants in the Galactic spheroid is shown to be important in determining the number-color histogram of stars brighter than B = 19 mag. This result is demonstrated by comparing a standard Galaxy model with observations of 391 stars in a field in the direction of Aquarius (l = 36.5 deg, b = -51.1 deg). More than 80 percent of the spheroid stars and 40 percent of all stars in this magnitude range and direction are predicted to be giants. At most, a few percent of the spheroid stars in the current sample can lie on the main sequence bluer than the turn-off onto the giant branch near B - V approximately 0.4. The available observations suggest that the blue tip of the horizontal branch of the spheroid must be sparsely populated about a factor of 10 less than would be expected if the color-magnitude diagram of the spheroid were the same as diagrams for any of the globular clusters M3, M13, or M92. The total dispersion in colors (measurement errors and intrinsic dispersion) has a standard deviation in B - V color that is less than 0.2 mag.

Bahcall, J. N.↗