SEARCH · Engineering Papers
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.
Methods of calibrating Thematic Mapper (TM) data by the use of ground based measurements are presented. Applications of the TM remote sensing data are discussed in addition to the ground truth measurement equipment and techniques.
LANDSAT Thematic Mapper P-data of Washington, D. C., Harrisburg, PA, and Salton Sea, CA are analyzed to determine magnitudes and causes of error in the geometric conformity of the data to known Earth surface geometry. Several tests of data geometry are performed. Intraband and interband correlation and registration are investigated, exclusive of map based ground truth. The magnitudes and statistical trends of pixel offsets between a single band's mirror scans (due to processing procedures) are computed, and the inter-band integrity of registration is analyzed. A line to line correlation analysis is included.
A comparison was made between ground data collected from Lake Chicot, Arkansas, and Thematic Mapper (TM) data collected on September 23, 1982. A preliminary analysis of limited data indicate tht Thematic Mapper data may be useful in monitoring suspended sediment and chlorophyll in a lake with high suspended sediment loads. Total suspended loads ranged from 168 to 508 mg/l. TM Band 3 appears to be most useful with Bands 1, 2 and 4 also containing useful information relative to suspended sediments. Considering water data only, Bands 1, 2 and 3 appear to provide similar information. Bands 3 and 4 are also significantly related. Bands 5 and 7 appear to have independent information content relative to the presence or absence of water. Insufficient range of water temperature ground truth data made an evaluation of TM Band 6 difficult.
Microwave sensor soil data were collected by aircraft over agricultural croplands. Multiple incident angle scatterometer data (13.3, 4.75, 1.6 and 0.4 GHz), passive radiometer data (L and C-band), and soil moisture ground truth measurements were collected coincidentally. Each sensor and angle of incidence was linearly analyzed against the measured soil moisture. For bare agricultural soils, the optimal single sensor for soil moisture preduction is the L-band passive radiometer. The effects of vegetation and differing surface roughness prove significant. When both bare and vegetated surfaces were studied, the masking due to the vegetation renders the single sensor approach ineffective in soil moisture prediction. Multisensor techniques are necessary to remotely measure soil moisture when a priori knowledge of vegetation is not available.
Successful ground truth support of U-2 overflights was been accomplished. Data have been reduced for 4 June 1984 and some of the results have been integrated into some of MSFC's efforts. Staccato lightning (multiply branched, single stroke flash with no continuing current) is prevalent within the rainfree region around the main storm updraft and this is believed to be important, i.e., staccato flashes might be an important indicator of severe storm electrification. Results from data analysis from two stations appear to indicate that charge center heights can be estimated from a combination of intercept data with data from the fixed laboratory at NSSL. An excellent data base has been provided for determining the sight errors and efficiency of NSSL's LLP system. Cloud structures, observable in a low radar reflectivity region and on a scale smaller than is currently resolved by radar, which appear to be related to electrical activity are studied.
A lightning detection system which has been operating along the East Coast since August 1982 is outlined. The system will prove to be one source of ground truth for lightning flashes detected from above clouds. The first absolute spectral irradiance measurements over a wide wavelength range were reported. The observations of lightning from a U2 aircraft are reviewed.
The Bayesian maximum likelihood parametric classifier has been tested against the data-based formulation designated 'linear discrimination analysis', using the 'GLIKE' decision and "CLASSIFY' classification algorithms in the Landsat Mapping System. Identical supervised training sets, USGS land use/land cover classes, and various combinations of Landsat image and ancilliary geodata variables, were used to compare the algorithms' thematic mapping accuracy on a single-date summer subscene, with a cellularized USGS land use map of the same time frame furnishing the ground truth reference. CLASSIFY, which accepts a priori class probabilities, is found to be more accurate than GLIKE, which assumes equal class occurrences, for all three mapping variable sets and both levels of detail. These results may be generalized to direct accuracy, time, cost, and flexibility advantages of linear discriminant analysis over Bayesian methods.
Three workshops have been conducted in order to define a research program which would in the course of five years lead to a concensus on methodologies for the conversion of satellite-measured irradiances into quantitative data concerning the earth's surface. Standardized data analysis algorithms would be the major product of this concensus. The three workshops have recommended the evaluation of retrospective satellite data, starting from the July, 1972 initial operation of Landsat-1, in order to demonstrate whether they can be used to detect climate-related or man-induced changes on the earth's surface quantitatively. Also suggested is the validation of current satellite data with ground truth campaigns in several different regions, and the preparation of an operational phase involving the testing of the selected data extraction algorithms for conversion of satellite-measured radiances into albedo, moisture, and vegetation data.
The capabilities of the Advanced Very High Resolution Radiometer (AVHRR) for land cover mapping were investigated by comparing the accuracy of land cover information for the Washington, DC area derived from NOAA-7 AVHRR data with that from Landsat Multispectral Scanner (MSS) data. Unsupervised Level I land cover classifications were performed for MSS and AVHRR data sets collected on July 11, 1981. A detailed accuracy assessment was conducted based on ground truth delineated on six USGS 7.5 minute series topographic maps. Preliminary results produced overall land cover classification accuracies of 75.6 percent and 76.1 percent for AVHRR and MSS, respectively. While the accuracies for predominant categories such as agriculture, forest, and urban were similar for both sensors, discrimination of the less commonly occurring categories such as barren, wetland, and water was improved with the MSS data set. The AVHRR, however, performed as well as or better than the MSS in classifying large homogeneous areas. The application of AVHRR data with its lower processing cost and more frequent worldwide coverage appears promising for global land cover mapping.
Multitemporal Thematic Mapper, Thematic Mapper Simulator, and detailed ground truth data were collected for a 9- by 11-km sample segment in Webster County, IA, in the summer of 1982. Three dates were acquired each with Thematic Mapper Simulator (June 7, June 23, and July 31) and Thematic Mapper (August 2, September 3, and October 21). The Thematic Mapper Simulator data were converted to equivalent TM count values using TM and TMS calibration data and model based estimates of atmospheric effects. The July 31, TMS image was compared to the August 2, TM image to verify the conversion process. A quantitative measure of proportion estimation variance (Fisher information) was used to evaluate the corn/soybeans separability for each TM band as a function of time during the growing season. The additional bands in the middle infrared allowed corn and soybeans to be separated much earlier than was possible with the visible and near-infrared bands alone. Using the TM and TMS data, temporal profiles of the TM principal components were developed. The greenness and brightness exhibited behavior similar to MSS greenness and brightness for corn and soybeans.
A four-channel multispectral scanner (MSS) carried aboard an aircraft was used to collect data along several flight paths over St. Joseph Bay, FL. Various classifications of benthic features were defined from the results of ground-truth observations. The classes were statistically correlated with MSS channel signal intensity using multivariate methods. Application of the classification measures to the MSS data set allowed computer construction of a detailed map of benthic features of the bay. Various densities of segrasses, various bottom types, and algal coverage were distinguished from water of various depths. The areal vegetation coverage of St. Joseph Bay was not significantly different from the results of a survey conducted six years previously, suggesting that seagrasses are a very stable feature of the bay bottom.
Multitemporal Thematic Mapper, Thematic Mapper Simulator, and detailed ground truth data were collected for a 9- by 11-km sample segment in Webster County, Iowa, in the summer of 1982. Three dates were acquired each with Thematic Mapper Simulator (June 7, June 23, and July 31) and Thematic Mapper (August 2, September 3, and October 21). The additional TM spectral bands in the middle infrared were found to substantially improve corn/soybean separability in both single date and multitemporal analyses.
A boiled-down version of major legal principles affecting the admissibility of data and products from remote sensing devices is presented. It is suggested that enhancements or classifications of digital data (from scanning devices or from digitized aerial photography) be proffered as evidence in a fashion similar to the manner in which maps from photogrammetric techniques are introduced as evidence. Every effort should be made to illucidate the processes by which digital data are analytically treated or manipulated. Remote sensing expert witnesses should be practiced in providing concise and clear explanations of both data and methods. Special emphasis should be placed on being prepared to provide a detailed accounting of steps taken to calibrate and verify spectral characteristics with ground truth.
It is immediately apparent from the examination of almost any synthetic aperture radar (SAR) data that the radar return is primarily a function of the topographic relief. Yet radar reflectance is dependent on both surface roughness and the dielectric constant of the surface material. These two parameters can in many cases be related to lithologic units. Thus, if the first-order terrain effects due to topographic relief could (in essence) be removed from the radar image, the SAR data might well be used for lithologic discrimination. Such an approach is evaluated. Landsat Thematic Mapper data along with ground truth are used to define training cells that characterize the various lithologic units in the area. By aggregating the radar data for these cells, curves of radar reflectance versus local incidence are estimated. The curves are then used to classify the test area. The results are compared with lithologic classification based upon multi-spectral (visible and infrared) data.
The primary goal of the project was to provide ground truth and manual interpretation of data from an experimental flight of the Airborne Infrared Spectrometer (AIS) for a naturally vegetated test site. Two field visits were made; one trip to note snow conditions and temporally related vegetation states at the time of the sensor overpass, and a second trip following acquisition of prints of the AIS images for field interpretation. Unfortunately, the ability to interpret the imagery was limited by the quality of the imagery due to the experimental nature of the sensor.
The initial characterization of the Thematic Mapper (TM) thermal band is reported including gain stability, gain relation to internal calibration, corrections for channel-to-channel and scan direction differences, an approximate comparison to ground truth, and a calculation of noise equivalent temperature difference. Updated calibration information is also presented.
Using selected instrumented areas at White Sands Missile Range, New Mexico as reference, radiometric calibration is to be effected on the sensors of LANDSAT 4, particularly the thematic mapper. Optical measurements made during a TM overpass are discussed. The radiances of selected large ground areas are measured in the spectral bandpasses of the TM; the total optical thickness of the atmosphere is measured in nine narrow spectral intervals. Ground truth in the form of reflectances collected for the alkalai flat region of gypsum and for the snow at White Sands is described.
Comparison of underflight data with satellite estimates of temperature revealed significant gain calibration errors. The source of the LANDSAT 5 band 6 error and its reproducibility is not yet adequately defined. The error can be accounted for using underflight or ground truth data. When underflight data are used to correct the satellite data, the residual error for the scene studied was 1.3K when the predicted temperatures were compared to measured surface temperature.