• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 2058
  • 879
  • 367
  • 211
  • 45
  • 41
  • 41
  • 41
  • 41
  • 41
  • 40
  • 29
  • 29
  • 28
  • 26
  • Tagged with
  • 4438
  • 4438
  • 893
  • 892
  • 402
  • 385
  • 384
  • 363
  • 354
  • 345
  • 335
  • 334
  • 330
  • 295
  • 294
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
281

Multispectral remote sensing of surficial materials in an arid environment

Munday, Timothy J. January 1985 (has links)
No description available.
282

Linear semi-empirical kernel-driven bidirectional reflectance distribution function models in monitoring semi-arid grasslands from space

Chopping, M. J. January 1998 (has links)
No description available.
283

BYU SAR: A Low Cost Compact Synthetic Aperture Radar

Long, David G., Jarrett, Bryan, Arnold, David V., Cano, Jorge 11 1900 (has links)
International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, Nevada / Synthetic Aperture Radar (SAR) systems are typically very complex and expensive. They generate enormous quantities of data, requiring very high capacity data storage, transmission, and processing systems. We have developed an experimental SAR system with a very simple design which includes near-real-time onboard processing. This system is based on recent developments in low-cost, high-rate analog-to-digital (A/D) and digital-to-analog (D/A) data conversion systems. Most of the system is based on off-the-shelf components. A very simple RF subsystem is used. The system has been successfully operated from a moving surface vehicle and exhibits a range resolution of 2.5 m though this could be improved to 1.5 m at the expense of higher sidelobes. The four look azimuth resolution is 0.4 m. This paper describes the system as well as our plans for upgrading the system for aircraft operation and improved resolution.
284

The use of remotely sensed LiDAR and multispectral imagery for modeling eastern redcedar biomass within North Eastern Kansas

Bryant, Johnny January 1900 (has links)
Master of Arts / Department of Geography / Kevin P. Price / Due in large part to changes in land management practices, eastern redcedar (Juniperus virginiana L.), a native Kansas conifer, is rapidly invading onto valuable rangelands. The suppression of fire and increase of intensive grazing, combined with the rapid growth rate, high reproductive output, and dispersal ability of the species have allowed it to dramatically expand beyond its original range. Based on its abundance and invasive nature there is a growing interest in harvesting this species for use as a biofuel. For economic planning purposes, density and biomass quantities for the trees are needed. Three methods are explored for mapping eastern redcedar and quantifying its biomass in Riley County, Kansas. First a comparison of plot-regression versus individual tree based techniques is conducted to determine the optimal approach for characterizing redcedar tree canopy using LiDAR (Light Detection and Ranging). Second a hybrid approach is utilized to characterize redcedar canopy biomass using LiDAR and high-resolution multispectral imagery. Finally, to explore alternative methods of characterizing the three-dimensional structure of redcedar canopy a comparison of “Structure from Motion” photogrammetric techniques and LiDAR is conducted. These methods showed promising results and proved to be useful in the forestry, range management, and bioenergy industries for better understanding the potential of invasive redcedar as a biofuel resource.
285

A Storm Water Runoff Investigation Using Gis and Remote Sensing

Jennings, Laura 08 1900 (has links)
Environmental controls are becoming more and more expensive to implement, so environmental management is becoming more technologically advanced and efficient through the adoption of new techniques and models. This paper reviews the potential for storm water runoff for the city of Denton, Texas and with the main objective to perform storm water runoff analyses for three different land use datasets; each landuse dataset created with a different methodology. Also analyzed was the difference between two North Central Texas Council of Governments land use datasets and my own land use dataset as a part of evaluating new and emerging remote sensing techniques. The results showed that new remote sensing techniques can help to continually monitor changes within watersheds by providing more accurate data.
286

Implementation of a Global Dust Physical Sea Surface Temperature Retrieval For Numerical Weather Prediction Applications

Oyola, Mayra I. 18 February 2017 (has links)
<p> This works presents the results for the first study to ever attempt to analyze the full potential and limitations of incorporating aerosols within a truly physical SST retrieval for operational weather forecasting purposes. This is accomplished through the application of a satellite sea surface temperature (SST) physical retrieval for satellite split-window and hyperspectral infrared (IR) sensors that allows a better representation of the atmospheric state under aerosol-laden conditions. The new algorithm includes 1) accurate specification of the surface emissivity that characterizes the surface leaving radiance and 2) transmittance and physical characterization of the atmosphere by using the Community Radiative transfer model (CRTM). This project includes application of the NEMS-Global Forecasting System Aerosol Component (NGAC) fields, which corresponds to the first global interactive atmosphere-aerosol forecast system ever implemented at NOAA&rsquo;s National Center for Environmental Prediction (NCEP). </p><p> A number of limiting factors were identified by analysing brightness temperatures and SST outputs biases as a function of latitude, zenith angle, wind and moisture for cases in January and November 2013. SST ouputs are validated against a bulk SST (Reynolds SST) and a parameterized SST derived from operational products and partly against observed measurements from the eastern Atlantic Ocean, which is dominated by Saharan dust throughout most of the year and that is also a genesis region for Atlantic tropical cyclones. These observations are obtained from the NOAA Aerosols and Ocean Science Expeditions (AEROSE). The improved physical SST methodology has the potential to allow for improved representation of the geophysical state under dust-laden conditions. </p>
287

Design of a bore sight camera for the lineate image near ultraviolet spectrometer (LINUS)

Cabezas, Rodrigo. 06 1900 (has links)
Approved for public release; distribution is unlimited. / The Lineate Image Near Ultraviolet Spectrometer (LINUS) is a spectral imager that works in the ultraviolet region of the spectrum. This thesis describes the latest of several steps in the development of this instrument. Due to the narrow field of view of the instrument, 2.5 x 0.5 degrees, an accurate pointing method is necessary; also, a scheme of quality evaluation of the post-processed spectral image is desirable. A way to achieve both goals was developed by designing and implementing the layout for two visual cameras, wide and narrow field of view, and a method to capture the images in order to perform the subsequent comparison with the processed spectral image. Since this is the first time the system is working in full-automated mode, a new wavelength calibration with the emission lines from a platinum hollow cathode lamp was performed and a new response curve for sulfur dioxide (SO2) was taken. Finally, laboratory and outdoor field observations were conducted to test the system integration. / Lieutenant, Chilean Navy
288

Time series analysis of vegetation dynamics and burn scar mapping at Smoky Hill Air National Guard Range, Kansas using moderate resolution satellite imagery

Williams, Danielle M. January 1900 (has links)
Master of Arts / Department of Geography / J. M. Shawn Hutchinson / Military installations are important assets for the proper training of armed forces. To ensure the continued viability of training lands, management practices need to be implemented to sustain the necessary environmental conditions for safe and effective training. For this study two analyses were done, a contemporary burn history and a time series analysis. The study area is Smoky Hill Air National Guard Range (ANGR), an Impact Area (within the range) and a non-military Comparison Site. Landsat 5 TM / 7 ETM+ imagery was used to create an 11 year composite burn history image. NDVI values were derived from MODIS imagery for the time series analysis using the statistical package BFAST. Results from both studies were combined to make conclusions about training impacts at Smoky Hill ANGR and determine if BFAST is a viable environmental management tool. Based on this study the training within Smoky Hill ANGR does not seem to be having a negative effect on the overall vegetation condition. It was also discovered that BFAST was able to accurately detect known vegetation disturbances. BFAST is a viable environmental management tool if the limitations are understood.
289

Cloud influence on radiative cooling over the Tibetan Plateau during the summer monsoon period

Unknown Date (has links)
The spatial and temporal variations of tropospheric longwave cooling, shortwave heating and cloud effects on these processes over the Tibetan Plateau during the summer monsoon season of 1988 are studied using infrared and visible measurements from the Indian geosynchronous satellite (INSAT). Estimates of surface temperature, surface albedo, cloud amount, cloud height, cloud water content, and effective radius of cloud drops are incorporated in a 27-band infrared model and a 38-band solar model to calculate radiative divergence profiles. The effects of cloudiness are parameterized in terms of water/ice contents and effective radius. Cloud effective radius is obtained through an optimization scheme which minimizes the top-of-atmosphere shortwave flux differences between INSAT visible measurements and estimates from the solar model. A theoretically consistent parameterization scheme is developed for calculating the cloud asymmetry parameter as a continuous function of wavelength and effective radius. / The mean radiative effect of cloudiness over the large-scale elevated plateau during the course of the summer monsoon is to cool the atmosphere. However, the cooling takes place by virtue of cloud-induced longwave cooling dominating cloud-induced shortwave heating. This is completely opposite of the conventional view in which cloud causes infrared warming and solar cooling. Vertically, cloud-induced radiative cooling is strongest in the middle troposphere with weaker cooling rates in the lower troposphere. Therefore, clouds contribute indirectly to an increase in atmospheric heating through reducing static stability and thus aid the release of latent heat by cloud systems. Plateau radiative cooling rates vary significantly through different monsoon phases, primarily due to variations in cloud forcing. / Source: Dissertation Abstracts International, Volume: 53-07, Section: B, page: 3542. / Major Professor: Eric A. Smith. / Thesis (Ph.D.)--The Florida State University, 1992.
290

Improving Satellite-Based Snowfall Estimation: A New Method for Classifying Precipitation Phase and Estimating Snowfall Rate

Unknown Date (has links)
In order to study the impact of climate change on the Earth's hydrologic cycle, global information about snowfall is needed. To achieve global measurements of snowfall over both land and ocean, satellites are necessary. While satellites provide the best option for making measurements on a global scale, the task of estimating snowfall rate from these measurements is a complex problem. Satellite-based radar, for example, measures effective radar reflectivity, Ze, which can be converted to snowfall rate, S, via a Ze-S relation. Choosing the appropriate Ze-S relation to apply is a complicated problem, however, because quantities such as particle shape, size distribution, and terminal velocity are often unknown, and these quantities directly affect the Ze-S relation. Additionally, it is important to correctly classify the phase of precipitation. A misclassification can result in order-of-magnitude errors in the estimated precipitation rate. Using global ground-based observations over multiple years, the influence of different geophysical parameters on precipitation phase is investigated, with the goal of obtaining an improved method for determining precipitation phase. The parameters studied are near-surface air temperature, atmospheric moisture, low-level vertical temperature lapse rate, surface skin temperature, surface pressure, and land cover type. To combine the effects of temperature and moisture, wet-bulb temperature, instead of air temperature, is used as a key parameter for separating solid and liquid precipitation. Results show that in addition to wet-bulb temperature, vertical temperature lapse rate also affects the precipitation phase. For example, at a near-surface wet-bulb temperature of 0°C, a lapse rate of 6°C km-1 results in an 86 percent conditional probability of solid precipitation, while a lapse rate of -2°C km-1 results in a 45 percent probability. For near-surface wet-bulb temperatures less than 0°C, skin temperature affects precipitation phase, although the effect appears to be minor. Results also show that surface pressure appears to influence precipitation phase in some cases, however, this dependence is not clear on a global scale. Land cover type does not appear to affect precipitation phase. Based on these findings, a parameterization scheme has been developed that accepts available meteorological data as input, and returns the conditional probability of solid precipitation. Ze-S relations for various particle shapes, size distributions, and terminal velocities have been developed as part of this research. These Ze-S relations have been applied to radar reflectivity data from the CloudSat Cloud Profiling Radar to calculate the annual mean snowfall rate. The calculated snowfall rates are then compared to surface observations of snowfall. An effort to determine which particle shape best represents the type of snow falling in various locations across the United States has been made. An optimized Ze-S relation has been developed, which combines multiple Ze-S relations in order to minimize error when compared to the surface snowfall observations. Additionally, the resulting surface snowfall rate is compared with the CloudSat standard product for snowfall rate. / A Dissertation submitted to the Department of Earth, Ocean and Atmospheric Science in partial fulfillment of the Doctor of Philosophy. / Spring Semester 2017. / March 31, 2017. / Atmospheric Science, Hydrology, Meteorology, Remote Sensing, Snowfall / Includes bibliographical references. / Guosheng Liu, Professor Directing Dissertation; Anke Meyer-Baese, University Representative; Mark A. Bourassa, Committee Member; Ming Cai, Committee Member; Philip G. Sura, Committee Member.

Page generated in 0.1017 seconds