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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.

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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Active Pixel Sensor (APS) based Star Tracker

Charge-Coupled Device (CCD) based star trackes provide reliable attitude estimation onboard most 3 axis stabilized spacecraft. The spacecraft attitude is calculated based on observed positions of stars, which are located and identified in a CCD image of the sky.

active↗
NASA NTRS1979

Very high speed processing: Applicability of peripheral devices to pixel-dependent tasks

Early options studied in the satisfaction of LACIE implementation computational demands are described as well as the ultimate selection and development of an array processing solution to the problem. The economic justification, as a function of required LANDSAT analysis, is provided. The suitability of such processors for LACIE and other applications is discussed.

Lyon, J. C.↗
NASA NTRS1979

Spatial quantification of maps or images - Cell size or pixel size implications

The paper discusses spatial quantification of maps or images. Spatial accuracies evaluated by mapping and inventory measures were observed with a range of cell sizes for a 10.36 sq km soil survey segment. The distribution of interboundary distances in a map was evaluated as unique, characterizing information; experimentally observed relationships between accuracy and cell size and interboundary distance distribution parameters and cell size led to a model of the process of spatial quantization. Grid positioning effects were evaluated and were significant only at the level of individual mapping units; two generations of 'universal' process models were derived, implemented, and evaluated.

Wehde, M. E.↗
NASA NTRS1980

Pure pixel classification software

Programs are described which permit classification runs with the LARSYS software to be made on images which have the ground truth field boundaries removed.

Wehmanen, O. A.↗
NASA NTRS1980

The multicategory case of the sequential Bayesian pixel selection and estimation procedure

A Bayesian technique for stratified proportion estimation and a sampling based on minimizing the mean squared error of this estimator were developed and tested on LANDSAT multispectral scanner data using the beta density function to model the prior distribution in the two-class case. An extention of this procedure to the k-class case is considered. A generalization of the beta function is shown to be a density function for the general case which allows the procedure to be extended.

Pore, M. D.↗
NASA NTRS1984

Regional analysis from data from heterogeneous pixels - Remote sensing of total dry matter production in the Senegalese Sahel

Nine predominantly cloud-free NOAA-7 advanced very high resolution radiometer images were obtained during a three-month period during the 1981 rainy season in the Sahel of Senegal. The 0.55-0.68 and 0.725-1.10-micron channels were used to form the normalized difference green leaf density vegetation index and the 11.5-12.5-micron channel was used as a cloud mask for each of the nine images. Changes in the normalized difference values among the various dates were closely associated with precipitation events. Six of the images spanning an eight-week period were used to generate a cumulative integrated index. Ground biomass samplings in the 30,000 sq km study area were used to assign total dry biomass classes to the cumulative index.

Tucker, C. J.↗
NASA NTRS1985

Strategies for analyzing mixed pixels in remotely sensed imagery

Two uncalibrated synthetic aperture radar (SAR) scenes from Death Valley, California, and two uncalibrated scenes from Owens Valley, California, were used to test a technique to identify and separate the primary factors associated with multipolarized radar image sets. Unique to the technique is the concept that varied types of radar polarization signatures are a result of the interaction of a few physical factors (e.g., roughness, volume scattering, and dielectric constant). Thus, the varied signatures observed in an image reflect the interaction between these factors. The objectives are to first separate the interaction of factors directly influencing the measurement and to attempt to identify these factors. Interpretation of the SAR image sets proceeds by testing models that hypothesize the cause and effect relations between those factors directly affecting the radar measurement and those features of interest to the interpreter. The results of our analysis indicated two consistent endmember types over all four image scenes. These types are defined by a high flat polarized signature near a level of 255 DN and a low level flat signature near 0 DN for all polarizations. Four other endmember types were also isolated. The spatial distribution of these endmember types indicates possible correspondence to surface volume scattering and changes in surface dielectric. However, the shapes of these endmember types were different from scene to scene.

Smith, M.↗
NASA NTRS1994

A technique for determining cloud free versus cloud contaminated pixels in satellite imagery

Weather forecasting has been called the second oldest profession. To do so accurately and with some consistency requires an ability to understand the processes which create the clouds, drive the winds, and produce the ever changing atmospheric conditions. Measurement of basic parameters such as temperature, water vapor content, pressure, windspeed and wind direction throughout the three dimensional atmosphere form the foundation upon which a modern forecast is created. Doppler radar, and space borne remote sensing have provided forecasters the new tools with which to ply their trade.

Wohlman, Richard A.↗