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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Digital rectification of ERTS multispectral imagery

Rectified ERTS multispectral imagery have been produced utilizing all digital techniques, as the first step toward producing precision corrected imagery. Errors arising from attitude and ephemeris sources have been corrected, and the resultant image is represented in a meter/meter mapping utilizing an intensity resampling technique. Early results from available data indicate negligible degradation of the photometric and resolution properties of the source data as a consequence of the geometric correction process. Work utilizing ground control points to produce precision rectified imagery, and including photometric corrections resulting from available sensor calibration data, is currently in progress.

Rifman, S. S.↗
NASA NTRS1974

Application of advanced signal processing techniques to the rectification and registration of spaceborne imagery

The development of an ERTS/MSS image processing system responsive to the needs of the user community is discussed. An overview of the TRW ERTS/MSS processor is presented, followed by a more detailed discussion of image processing functions satisfied by the system. The particular functions chosen for discussion are evolved from advanced signal processing techniques rooted in the areas of communication and control. These examples show how classical aerospace technology can be transferred to solve the more contemporary problems confronting the users of spaceborne imagery.

Caron, R. H.↗
NASA NTRS1977

Digital image-rectification system

System removes spatial distortions from data and brings data into conformance with Universal Transverse Mercator map projection, produces digital output products suitable for further machine processing and analysis, and fills need for geometrically corrected Landsat multispectral scanner digital data in several remote sensing application areas.

Van Wie, P. H.↗
NASA NTRS1979

Error detection and rectification in digital terrain models

Digital terrain models produced by computer correlation of stereo images are likely to contain occasional gross errors in terrain elevation. These errors typically result from having mismatched sub-areas of the two images, a problem which can occur for a variety of image- and terrain-related reasons. Such elevation errors produce undesirable effects when the models are further processed, and should be detected and corrected as early in the processing as possible. Algorithms have been developed to detect and correct errors in digital terrain models. These algorithms focus on the use of constraints on both the allowable slope and the allowable change in slope in local areas around each point. Relaxation-like techniques are employed in the iteration of the detection and correction phases to obtain best results.

Hannah, M. J.↗
NASA NTRS1982

Registration and rectification needs of geology

Geologic applications of remotely sensed imaging encompass five areas of interest. The five areas include: (1) enhancement and analysis of individual images; (2) work with small area mosaics of imagery which have been map projection rectified to individual quadrangles; (3) development of large area mosaics of multiple images for several counties or states; (4) registration of multitemporal images; and (5) data integration from several sensors and map sources. Examples for each of these types of applications are summarized.

Chavez, P. S., Jr.↗
NASA NTRS1982

Oceanographic satellite remote sensing: Registration, rectification, and data integration requirements

The problem of data integration in oceanography is discussed. Recommendations are made for technique development and evaluation, understanding requirements, and packaging techniques for speed, efficiency and ease of use. The primary satellite sensors of interest to oceanography are summarized. It is concluded that imaging type sensors make image processing an important tool for oceanographic studies.

Nichols, D. A.↗
NASA NTRS1987

A post-processing system for automated rectification and registration of spaceborne SAR imagery

An automated post-processing system has been developed that interfaces with the raw image output of the operational digital SAR correlator. This system is designed for optimal efficiency by using advanced signal processing hardware and an algorithm that requires no operator interaction, such as the determination of ground control points. The standard output is a geocoded image product (i.e. resampled to a specified map projection). The system is capable of producing multiframe mosaics for large-scale mapping by combining images in both the along-track direction and adjacent cross-track swaths from ascending and descending passes over the same target area. The output products have absolute location uncertainty of less than 50 m and relative distortion (scale factor and skew) of less than 0.1 per cent relative to local variations from the assumed geoid.

Curlander, John C.↗
NASA NTRS1987

Rectification of terrain induced distortions in radar imagery

This paper describes a technique to generate geocoded synthetic aperture radar (SAR) imagery corrected for terrain induced geometric distortions. This algorithm transforms the raw slant range image, generated by the signal processor, into a map registered product, resampled to either Universal Transverse Mercator (UTM) or Polar Stereographic projections, and corrected for foreshortening. The technique utilizes the space platform trajectory information in conjunction with a digital elevation map (DEM) of the target area to generate an ortho-radar map with near-autonomous operation. The current procedure requires only two to three tie-points to compensate for the platform position uncertainty that results in translational error between the image and the DEM. This approach is unique in that it does not require generation of a simulated radar image from the DEM or a grid of tie-points to characterize the image-to-map distortions. Rather, it models the inherent distortions based on knowledge of the radar data collection characteristics, the signal Doppler parameters, and the local terrain height to automatically predict the registration transformation. This algorithm has been implemented on a minicomputer system equipped with an array processor and a large random-access memory to optimize the throughput.

Kwok, Ronald↗
NASA NTRS1991

Geometric rectification and geocoding of JPL's AIRSAR data over hilly terrain

A post-processing system was developed to georeference and geocode airborne synthetic aperture radar (SAR) data collected by the JPL-Airborne SAR (AIRSAR) System over hilly terrain during the 1990 MAESTRO1 campaign. Georectification relates image coordinates and object coordinates while the geocoding involves resampling. The georectification method uses a hybrid method based upon a number of navigational parameters and minimal two ground-control points which are referenced in both image and map space. The calculation of the intersection of the SAR signal wavefront and a digital elevation model allowed, within certain error bounds, acquisition of the object-to-image and image-to-object relationships.

Degroof, H.↗
NASA NTRS1991

Radiometric rectification - Toward a common radiometric response among multidate, multisensor images

A method is developed for relating scene digital counts among several images of the same scene by identifying radiometric control sets with mean reflectances that are basically constant. The average digital-count values of the control sets are utilized to compute linear transforms that relate digital count values between images. Two Landsat TM images are studied by means of the technique using simulations of a wide range of atmospheric conditions. In the visible and near-IR bands the algorithm effectively adjusts the surface reflectance for the effects of relative atmospheric differences to within 1 percent. The proposed method is found to be an effective relative correction procedure that can be used when atmospheric optical-depth data and calibration coefficients are not available.

Hall, F. G.↗
NASA NTRS1992

Geometric ortho-rectification and generation of sigma(0) image products from multiple incidence synthetic aperture radar images

The results of the first phase of a cooperative effort in geometric orthorectification and generation of sigma(0) images of multiple incidence SAR images are presented. The geometric accuracy of the final image products is approximately 18 m or 1.5 pixels. A method for registering radar imagery collected from an airborne platform to an existing digital elevation model despite the effects of unmodeled variations in the flight path of the platform is demonstrated. The results indicate the requirements for a more detailed digital elevation model.

Curlander, James↗
NASA NTRS1993

A direct current rectification scheme for microwave space power conversion using traveling wave electron acceleration

The formation of the Vision-21 conference held three years ago allowed the present author to reflect and speculate on the problem of converting electromagnetic energy to a direct current by essentially reversing the process used in traveling wave tubes that converts energy in the form of a direct current to electromagnetic energy. The idea was to use the electric field of the electromagnetic wave to produce electrons through the field emission process and accelerate these electrons by the same field to produce an electric current across a large potential difference. The acceleration process was that of cyclotron auto-resonance. Since that time, this rather speculative ideas has been developed into a method that shows great promise and for which a patent is pending and a prototype design will be demonstrated in a potential laser power beaming application. From the point of view of the author, a forum such as Vision-21 is becoming an essential component in the rather conservative climate in which our initiatives for space exploration are presently formed. Exchanges such as Vision-21 not only allows us to deviate from the 'by-the-book' approach and rediscover the ability and power in imagination, but provides for the discussion of ideas hitherto considered 'crazy' so that they may be given the change to transcend from the level of eccentricity to applicability.

Manning, Robert M.↗
NASA NTRS2004

CO2 Budget and Rectification Airborne Study

The main purpose of this award was to supply a platform for the airborne measurements of gases associated with the CO2 Budget and Regional Airborne Study (COBRA). The original program was to consist of three field programs: the first was to be in 1999, the second in 2000, and the third in 2001. At the end of the second field program, it was agreed that the science could better be served by making the measurements in northern Brazil, rather than in North America. The final North American program would be postponed until after two field programs in Brazil. A substantial amount of effort was diverted into making plans and preparations for the Brazil field programs. The Brazil field programs were originally scheduled to take place in the Fall of 2002 and Spring of 2003. Carrying out the field program in Brazil was going to logistically much more involved than a program in the US. Shipping of equipment, customs, and site preparations required work to begin many months prior to the actual measurement program. Permission to fly in that country was also not trivial and indeed proved to be a major obstacle. When we were not able to get permission to fly in Brazil for the 2002 portion of the experiment, the program was pushed back to 2003. When permission by the Brazilian government was not given in time for a Spring of 2003 field program, the experiment was postponed again to begin in the Fall of 2003.

Grainger, C. A.↗
NASA NTRS1993

High Efficiency Synchronous Rectification in Spacecraft

This paper examines the implementaion of MOSFETs as synchronous rectifiers which results in a substantial improvement in power processing efficency and therefore may result in significant reduction of spacecraft mass and volum for the same payload.

Spacecraft Power↗
NASA NTRS2008

Acoustic Rectification in Dispersive Media

It is shown that the shapes of acoustic radiation-induced static strain and displacement pulses (rectified acoustic pulses) are defined locally by the energy density of the generating waveform. Dispersive properties are introduced analytically by assuming that the rectified pulses are functionally dependent on a phase factor that includes both dispersive and nonlinear terms. The dispersion causes an evolutionary change in the shape of the energy density profile that leads to the generation of solitons experimentally observed in fused silica.

Cantrell, John H.↗