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At least 343 records · Page 19

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NASA NTRS1983

Progress In The Scene-To-Map Registration Investigation

The geometric accuracy of the scene-to-map registration process for P-format LANDSAT MSS data for scenes from Kansas and Louisiana/Mississippi is discussed. Large scale row and column bias values and row and column standard deviation values were measured for the P-format data sets indicating a poor georegistration accuracy for these geometrically corrected LANDSAT MSS scenes. Experimental work is underway with A-format LANDSAT MSS scenes from the same locations to examine the influence of the number of ground control points and the spatial distribution of ground control points on geometric registration accuracy. An early conclusion from this work is that the root mean square approach for assessing how well the ground control points fit the mapping equations measures a different aspect of georegistration accuracy than does the approach of evaluating the bias (offset) and standard deviation using independently chosen ground reference points.

Dow, D. D.↗

NASA NTRS1983

A simulation study of scene confusion factors in sensing soil moisture from orbital radar

Simulated C-band radar imagery for a 124-km by 108-km test site in eastern Kansas is used to classify soil moisture. Simulated radar resolutions are 100 m by 100 m, 1 km by 1km, and 3 km by 3 km. Distributions of actual near-surface soil moisture are established daily for a 23-day accounting period using a water budget model. Within the 23-day period, three orbital radar overpasses are simulated roughly corresponding to generally moist, wet, and dry soil moisture conditions. The radar simulations are performed by a target/sensor interaction model dependent upon a terrain model, land-use classification, and near-surface soil moisture distribution. The accuracy of soil-moisture classification is evaluated for each single-date radar observation and also for multi-date detection of relative soil moisture change. In general, the results for single-date moisture detection show that 70% to 90% of cropland can be correctly classified to within +/- 20% of the true percent of field capacity. For a given radar resolution, the expected classification accuracy is shown to be dependent upon both the general soil moisture condition and also the geographical distribution of land-use and topographic relief. An analysis of cropland, urban, pasture/rangeland, and woodland subregions within the test site indicates that multi-temporal detection of relative soil moisture change is least sensitive to classification error resulting from scene complexity and topographic effects.

Ulaby, F. T.↗

NASA NTRS1982

Accomplishments of the NASA Johnson Space Center portion of the soil moisture project in fiscal year 1981

The NASA/JSC ground scatterometer system was used in a row structure and row direction effects experiment to understand these effects on radar remote sensing of soil moisture. Also, a modification of the scatterometer system was begun and is continuing, to allow cross-polarization experiments to be conducted in fiscal years 1982 and 1983. Preprocessing of the 1978 agricultural soil moisture experiment (ASME) data was completed. Preparations for analysis of the ASME data is fiscal year 1982 were completed. A radar image simulation procedure developed by the University of Kansas is being improved. Profile soil moisture model outputs were compared quantitatively for the same soil and climate conditions. A new model was developed and tested to predict the soil moisture characteristic (water tension versus volumetric soil moisture content) from particle-size distribution and bulk density data. Relationships between surface-zone soil moisture, surface flux, and subsurface moisture conditions are being studied as well as the ways in which measured soil moisture (as obtained from remote sensing) can be used for agricultural applications.

Paris, J. F.↗

NASA NTRS1984

Effects of Vegetation Canopy Structure on Microwave Scattering

The role of canopy structure on microwave backscattering is studied. Structure refers to the size, orientation, and vertical placement of scatterers in the canopy. Models to predict the backscattering coefficient, SIGMAO, of vegetation with explicit biophysical and explicit polarization-dependent parameters were developed. Preparation for field measurements with radar scatterometers was completed. Technical progress included: (1) the modification of the Attema and Ulaby (1977) model and its multilayer variation by Hoekman et al. (1983) to include polarization explicitly (i.e., to allow for separate backscattering cross sections, SIGMA, and extinction cross sections, Q, for each polarization), (2) the investigation of the modified model to isolate canopy element orientation parameters by the rationing of SIGMAO measurements for different polarization combinations, (3) the development of expressions for bistatic scattering and canopy-substrate scattering to supplement the models, (4) the performance of sensitivity analyses on these models, (5) the modification of the Attema and Ulaby model to alloy for changes, (6) the use of the modified model with a seasonal corn data set from Kansas (Eger et al., 1983), and (7) the initiation of preparations for empirical measurements with radar spectrometer and the Mobile Radar Scatterometer in irrigated cropland to test the models.

Paris, J. F.↗

NASA NTRS1984

Study of Thematic Mapper and Multispectral Scanner Data Applications

The U.S. Geological Survey EROS Data Center evaluated the utility of LANDSAT multispectral scanner (MSS) and Thematic Mapper (TM) data for natural resource assessment and land cover information, emphasizing manual interpretation and digital classification of the data for U.S. Department of the Interior applications. In most cases, substantially more information was derived from TM data than from MSS data. The test areas included Washington, D.C. and prairie regions of South Dakota and Kansas.

Sadowski, F. G.↗

NASA NTRS1984

The influence of the number of ground control points on the scene-to-map registration accuracy

The optimum number of ground control points required to rectify a full scene or a portion of a LANDSAT MSS scene was investigated using data from southeastern Louisiana/southwestern Mississippi and eastern Kansas. The ground control points utilized were randomly distributed across the partial or full scene. This work suggest that 24 round control points are more than adequate to rectify a partial or full scene of LANDSAT MSS data. The error incurred in choosing ground control points representing artificial versus natural features was also studied.

Dow, D. D.↗

NASA NTRS1985

Test and evaluation plan for the Centralized Storm Information System

The installation of the Centralized Storm Information System (CSIS) at the NOAA operational complex in Kansas City, Missouri is described. This complex includes the National Severe Storms Forecast center and a Satellite Field Service Station which is denoted in this research plan as NSSFC. CSIS computers will act in concert to merge analyze the many data sets needed to forecast severe convective storms. Specific aspects of CSIS are evaluated against the CSIS objectives. The functions to be evaluated characterize the attributes of a generalized interactive computer system. A major development in the CSIS program will allow communication between CSIS and the NSSFC Eclipse computer.

Source record↗

NASA NTRS1984

Potentials for change detection using Seasat synthetic aperture radar data

The use of synthetic aperture radar (SAR) images for detecting change on the earth's surface is highly dependent on target orientation, azimuth angle, and sensor depression angle. SAR data can be used for change detection when consistency is maintained in radar wavelength, polarization, azimuth directions, and off-nadir depression angle. The interaction of these parameters and the imaged surface for change detection are shown in examples drawn from (1) Los Angeles, CA, (2) southern Florida, (3) Imperial Valley, CA, (4) a desert region west of Tucson, AZ, and (5) western Kansas. SAR imagery is used to emphasize the geometric form, and roughness, of the earth's surface. As changes in the roughness of the surface occur over time, temporal SAR images will indicate those differences. Several guidelines for change detection studies using imaging radar are derived from the examples.

Bryan, M. L.↗

NASA NTRS1983

A simulation study of the effects of land cover and crop type on sensing soil moisture with an orbital C-band radar

Simulated C-band radar imagery for a 124-km by 108-km test site in eastern Kansas is used to classify soil moisture. Simulated radar resolutions are 100 m by 100 m, 1 km by 1 km, and 3 km by 3 km, and each is processed using more than 23 independent samples. Moisture classification errors are examined as a function of land-cover distribution, field-size distribution, and local topographic relief for the full test site and also for subregions of cropland, urban areas, woodland, and pasture/rangeland. Results show that a radar resolution of 100 m by 100 m yields the most robust classification accuracies.

Dobson, M. C.↗

NASA NTRS1984

The role of an apparent mesoscale frontogenetic circulation in squall line initiation

The present investigation is concerned with the nature and apparent origin of a mesoscale clear zone and associated frontal line convection (a line of cumulus congestus clouds along an intensifying cold front) which appeared just prior to the explosive development of a line of severe thunderstorms at the cold front. It is pointed out that the clear zone formed immediately behind the cold front in southeastern Kansas and northeastern Oklahoma during the afternoon of April 16, 1982. Sequential displays of GOES-East satellite imagery are considered. The mechanism which seems to explain best the observations is a thermally direct frontogenetic circulation resulting from the combined effects of the synoptic-scale wind deformation field and mesoscale differential sensible heating.

Koch, S. E.↗

NASA NTRS1985

An observational study of a mesoscale area of convection under weak synoptic-scale forcing

This is a case study of a mesoscale area of convection which began at night over western Kansas on September 2, 1982 and lasted until the afternoon of September 3. Evidence from analyses of surface, upper-air radar, and satellite observations suggests that the thunderstorms probably formed in response to the lifting of an elevated layer of conditional instability. The lifting can be attributed qualitatively to quasi-geostrophic ascending motion resulting from a shallow layer of warm advection near 60 kPa. Two possible sources of moisture were midlevel moisture which had been advected around an upstream ridge and a localized area of turbulent transport of water vapor from below. The convective event could not have been forecast with synoptic-scale, mandatory-level analyses alone; it was difficult to explain even with detailed analyses at other levels.

Bluestein, H. B.↗

NASA NTRS1985

Boundary layer control of nocturnal convection associated with a synoptic scale system

Well defined nocturnal convection, together with distinct maximum precipitation events in Nebraska, were associated with strong diurnal wind oscillations at 850 mb in Oklahoma, Kansas and Missouri in the present study of pronounced precipitation and low level circulation variations over the Great Plains on May 5-10, 1979. A numerical prediction model, used to relate boundary layer flow modulations to synoptic scale flow for this case, is driven by a diurnal cycle. Experimental forecasts displayed diurnal wind modulations at 500 m, with rising motions of the order of 4 cm/sec at the 2200 m level, along the leading edge of the nocturnal jet.

Astling, E. G.↗

NASA NTRS1984

A case study on the application of geosynchronous satellite infrared data to estimate soil moisture

The use of GOES IR temperature data to estimate soil moisture content is discussed and demonstrated, modifying the procedure proposed by Wetzel et al. (1984) to provide for incorporation of independent measurements of vegetation biomass, geostrophic wind speed, and surface dewpoint. Data acquisition, processing, and the statistical approach employed are described; data for Kansas and Nebraska during a six-day period in July 1978 are analyzed; and a statistical relationship between observed surface temperature and antecedent precipitation index is established. The results are presented in tables, graphs, and maps, and the regression procedure is found to predict antecedent precipitation with statistically significant precision.

Woodward, R. H.↗

NASA NTRS1985

Evaluation of space SAR as a land-cover classification

The multidimensional approach to the mapping of land cover, crops, and forests is reported. Dimensionality is achieved by using data from sensors such as LANDSAT to augment Seasat and Shuttle Image Radar (SIR) data, using different image features such as tone and texture, and acquiring multidate data. Seasat, Shuttle Imaging Radar (SIR-A), and LANDSAT data are used both individually and in combination to map land cover in Oklahoma. The results indicates that radar is the best single sensor (72% accuracy) and produces the best sensor combination (97.5% accuracy) for discriminating among five land cover categories. Multidate Seasat data and a single data of LANDSAT coverage are then used in a crop classification study of western Kansas. The highest accuracy for a single channel is achieved using a Seasat scene, which produces a classification accuracy of 67%. Classification accuracy increases to approximately 75% when either a multidate Seasat combination or LANDSAT data in a multisensor combination is used. The tonal and textural elements of SIR-A data are then used both alone and in combination to classify forests into five categories.

Brisco, B.↗

NASA NTRS1986

Light interception and leaf area estimates from measurements of grass canopy reflectance

Grassland is a major component of the earth's available land. The vast area and remoteness of this ecosystem makes it difficult to assess its condition and monitor productivity by traditional methods. Remote sensing potentially offers a rapid nondestructive approach for monitoring such ecosystems. A study was carried out in a tallgrass prairie site near Manhattan, Kansas, during the 1983 and 1984 seasons to investigate the feasibility of estimating light interception and green leaf area index (LAI) from measurements of canopy multispectral reflectance. Greenness (Gn) index was found to be strongly correlated with intercepted photosynthetically active radiation (PAR). Two methods, a direct regression (RGR) and an indirect approach (IND), were used to estimate LAI from Gn index. The LAI values estimated by RGR method were consistently lower than the measured ones; however, good agreement was obtained between the LAI values estimated by IND method and the measured LAI. This suggests that Gn transformation of canopy spectral reflectance is more closely related to the fraction of intercepted PAR by green foliage than the quantity of green LAI.

Asrar, G.↗

NASA NTRS1986

Wind profiler data in a mesoscale experiment from a meteorological perspective

During May and June of 1985, the Oklahoma-Kansas Preliminary Regional Experiment of STORM-Central (OK PRE-STORM) was carried out, with the major objectives of learning more about mesoscale convective systems (MCSs) and gaining experience in the use of new sensing systems and measurement strategies that will improve the design of STORM-Central. Three 50-MHz wind profilers were employed in a triangular array with sides about 275 km. It is far too soon to report any results of this effort, for it has barely begun. The purpose here is to show some examples of the data, some of the surrounding conventional data, and to discuss some of the issues important to meteorologists in evaluating the contribution of the profiler data. The case of 10 to 11 June 1985, featuring a major squall line system which crossed the dense observing network from northwest to southeast, passing the Liberal site about 2230 GMT/10 June, the McPherson site about 0100 GMT/11 June, and Wichita about 0300 GMT/11 June is discussed. Radar and satellite data show that the system was growing rapidly when it passed Liberal, and was large and mature when it passed through McPherson and Wichita. The radar depiction of the system during this stage is given, with the McPherson site in the intense convective echoes near the leading edge at 01 GMT and in the stratiform precipitation at 03 GMT. The profiler wind data for a 9-hour period encompassing the squall line passage at each site are given.

Zipser, E. J.↗

NASA NTRS1987

Investigation of dynamic ground effect

An experimental investigation of dynamic ground effect was conducted in the Univ. of Kansas wind tunnel using delta wings of 60, 70, 75 deg sweep; the XB-70 wing; and the F-104A wing. Both static and dynamic tests were made. Test data were compared to other test data, including dynamic flight test data of the XB-70 and F-104A. Limited flow visualization test were conducted. A significant dynamic effect was found for highly swept delta wings.

Chang, Ray Chung↗

NASA NTRS1987

An experimental investigation of dynamic ground effect

Sixty degree delta wing, F-106B, and XB-70 models with and without flap deflections were tested in static and dynamic ground effect in the 36 by 51 inch subsonic wind tunnel at the University of Kansas. Dynamic ground effect was measured with movable sting support. For flow visualization, a tufted wire grid was mounted on the movable sting behind the model. Tests results showed that the lift and drag increments in dynamic ground effect were always lower than the static values. Effect of the trailing-edge flap deflections on lift increments was slight. The fuselage reduced the lift increments at a given ground height. From flow visualization under static conditions, the vortex core was seen to enlarge as the ground approached.

Lee, Pai Hung↗