The GPS Assimilator: a Method for Upgrading Existing GPS User Equipment to Improve Accuracy, Robustness, and Resistance to Spoofing

Preprint of the 2010 ION GNSS Conference Portland, OR, September 21–24, 2010A conceptual method is presented for upgrading existing GPS user equipment, without requiring hardware or software modifications to the equipment, to improve the equipment’s position, velocity, and time (PVT) accuracy, to increase its PVT robustness in weak-signal or jammed environments, and to protect the equipment from counterfeit GPS signals (GPS spoofing). The method is embodied in a device called the GPS Assimilator that couples to the radio frequency (RF) input of an existing GPS receiver. The Assimilator extracts navigation and timing information from RF signals in its environment—including non-GNSS signals—and from direct baseband aiding provided, for example, by an inertial navigation system, a frequency reference, or the GPS user. The Assimilator optimally fuses the collective navigation and timing information to produce a PVT solution which, by virtue of the diverse navigation and timing sources on which it is based, is highly accurate and inherently robust to GPS signal obstruction and jamming. The Assimilator embeds the PVT solution in a synthesized set of GPS signals and injects these into the RF input of a target GPS receiver for which an accurate and robust PVT solution is desired. A prototype software-defined Assimilator device is presented with three example applications.Aerospace Engineerin

Responses of Upland Herpetofauna to the Restoration of Carolina Bays and Thinning of Forested Bay Margins

Research on the effects of wetland restoration on reptiles and amphibians is becoming more common, but almost all of these studies have observed the colonization of recently disturbed habitats that were completely dry at the time of restoration. In a similar manner, investigations herpetofaunal responses to forest management have focused on clearcuts, and less intensive stand manipulations are not as well studied. To evaluate community and population responses of reptiles and amphibians to hydrology restoration and canopy removal in the interior of previously degraded Carolina bays, I monitored herpetofauna in the uplands adjacent to six historically degraded Carolina bays in the at the Savannah River Site (SRS) in South Carolina for four years after restoration. To evaluate the effects of forest thinning on upland herpetofauna, forests were thinned in the margins of three of these bays. I used repeated measures ANOVA to compare species richness and diversity and the abundance of selected species and guilds between these bays and with those at three reference bays that were not historically drained and three control bays that remained degraded. I also used Non-metric Multidimensional Scaling (NMDS) to look for community-level patterns based treatments I did not detect any differences in diversity or overall abundance of reptiles or amphibians between the four treatments, and NMDS did not indicate any patterns of community structure based on treatment. I captured eleven South Carolina species of conservation concern at the twelve bays, including juvenile Carolina gopher frogs (Rana capito) at two restored bays. Adult gopher frogs have only rarely been documented on the SRS despite intensive, long-term sampling at several wetlands, and successful recruitment is even rarer. Southern toads (Bufo terrestris) responded quickly to bay restoration, and gopher frog recruitment can be considered an indication of habitat quality. Because many of these species are highly philopatric and have limited dispersal ability, four years may be too soon to see changes in the herpetofaunal community, especially since restoration improved existing habitat rather than restoring uninhabitable sites. Pre-restoration sampling and long-term monitoring would allow more firm conclusions to be made. Forest thinning reduced the most common reptile, the green anole (Anolis carolinensis), a generalist lizard not especially sensitive to an open canopy or to harvest operations. Increased red imported fire ant (Solenopsis invicta) populations in disturbed areas and open canopies could be a factor, though more research is needed on the effects of fire ants on herpetofauna

Responses of Upland Herpetofauna to the Restoration of Carolina Bays and Thinning of Forested Bay Margins

Research on the effects of wetland restoration on reptiles and amphibians is becoming more common, but almost all of these studies have observed the colonization of recently disturbed habitats that were completely dry at the time of restoration. In a similar manner, investigations herpetofaunal responses to forest management have focused on clearcuts, and less intensive stand manipulations are not as well studied. To evaluate community and population responses of reptiles and amphibians to hydrology restoration and canopy removal in the interior of previously degraded Carolina bays, I monitored herpetofauna in the uplands adjacent to six historically degraded Carolina bays in the at the Savannah River Site (SRS) in South Carolina for four years after restoration. To evaluate the effects of forest thinning on upland herpetofauna, forests were thinned in the margins of three of these bays. I used repeated measures ANOVA to compare species richness and diversity and the abundance of selected species and guilds between these bays and with those at three reference bays that were not historically drained and three control bays that remained degraded. I also used Non-metric Multidimensional Scaling (NMDS) to look for community-level patterns based treatments I did not detect any differences in diversity or overall abundance of reptiles or amphibians between the four treatments, and NMDS did not indicate any patterns of community structure based on treatment. I captured eleven South Carolina species of conservation concern at the twelve bays, including juvenile Carolina gopher frogs (Rana capito) at two restored bays. Adult gopher frogs have only rarely been documented on the SRS despite intensive, long-term sampling at several wetlands, and successful recruitment is even rarer. Southern toads (Bufo terrestris) responded quickly to bay restoration, and gopher frog recruitment can be considered an indication of habitat quality. Because many of these species are highly philopatric and have limited dispersal ability, four years may be too soon to see changes in the herpetofaunal community, especially since restoration improved existing habitat rather than restoring uninhabitable sites. Pre-restoration sampling and long-term monitoring would allow more firm conclusions to be made. Forest thinning reduced the most common reptile, the green anole (Anolis carolinensis), a generalist lizard not especially sensitive to an open canopy or to harvest operations. Increased red imported fire ant (Solenopsis invicta) populations in disturbed areas and open canopies could be a factor, though more research is needed on the effects of fire ants on herpetofauna

Development and Demonstration of a TDOA-Based GNSS Interference Signal Localization System

Background theory, a reference design, and demonstration results are given for a Global Navigation Satellite System (GNSS) interference localization system comprising a distributed radio-frequency sensor network that simultaneously locates multiple interference sources by measuring their signals’ time difference of arrival (TDOA) between pairs of nodes in the network. The end-to-end solution offered here draws from previous work in single-emitter group delay estimation, very long baseline interferometry, subspace-based estimation, radar, and passive geolocation. Synchronization and automatic localization of sensor nodes is achieved through a tightly-coupled receiver architecture that enables phase-coherent and synchronous sampling of the interference signals and so-called reference signals which carry timing and positioning information. Signal and crosscorrelation models are developed and implemented in a simulator. Multiple-emitter subspace-based TDOA estimation techniques are developed as well as emitter identification and localization algorithms. Simulator performance is compared to the CramérRao lower bound for single-emitter TDOA precision. Results are given for a test exercise in which the system accurately locates emitters broadcasting in the amateur radio band in Austin, TX.Aerospace Engineering and Engineering Mechanic

Validity and Diagnostic Utility of the Learning Behaviors Scale

Psychological assessment is a critical component in educational decision making and planning; therefore it is important to investigate the validity and diagnostic utility of the tools that we use. The current study examined the construct validity and diagnostic utility of the Learning Behaviors Scale (LBS; McDermott, Green, Francis, & Stott, 1999). Two hundred and seventy-three third grade students were rated by their classroom teacher using the LBS. LBS data were analyzed along with TerraNova achievement scores and In View Cognitive Skills Index. Overall, statistically significant distinct group differences were found for the LBS between the Gifted and Typical groups, as well as the Gifted Referred (students screened, but not identified as gifted) and Typical groups supporting construct validity. However, no statistically significant results were found between the Gifted and Gifted Referred groups. Moderate support was found for the incremental predictive validity for LBS scores. The LBS Total score captured statistically significant variance (1.5% to 5.3%) in academic achievement above and beyond that of the Cognitive Skills Index. Similarly, the LBS factor scores added 3.1% to 6.5% of variance in achievement scores beyond the Cognitive Skills Index. Finally, LBS scores were unable to correctly classify individual group membership for the Gifted and Gifted Referred groups. However, a critical limitation was proposed as a potential reason for the limited support and lack of discriminant validity for the use of the LBS with above average students. A ceiling effect was observed for the LBS Total and factor scores among the Gifted Referred and Gifted groups, which likely limited the range of scores and impacted correlations and variability

Analysis of Ionospheric Scintillations using Wideband GPS L1 C/A Signal Data

A non-real-time GPS receiver has been developed and tested for use in scintillation analysis. The receiver consists of a digital storage receiver and non-real-time software acquisition and tracking algorithms. The goal of this work is to shed light on the behavior of strongly scintillating signals: signals which cause conventional GPS receivers to lose carrier lock. The receiver collects wideband GPS L1 digital data sampled at 5.7 MHz using an RF front-end and stores it on disk for post-processing. It processes the data off-line to determine carrier signal amplitude and phase variations during scintillations. The main processing algorithms are traditional code delay and carrier frequency acquisition algorithms and special signal processing algorithms that effectively function as a delay-locked loop and phase-locked loop. The tracking algorithms use non-causal smoothing techniques in order to optimally reconstruct the phase and amplitude variations of a scintillating signal. These techniques are robust against the deep power fades and strong phase fluctuations characteristic of scintillating signals. To test the receiver, scintillation data were collected in Cauchoeira Paulista, Brazil, from December 4 to 6, 2003. The data set spans several hours and includes times when one or more satellite signals are scintillating. The smoothing algorithm has been used to determine the carrier amplitude and phase time histories of the scintillating signals along with the distortion of the pseudorandom noise (PRN) code’s autocorrelation function. These quantities provide a characterization of scintillation that can be used to study the physics of scintillations or to provide off-line test cases to evaluate a tracking algorithm’s ability to maintain signal lock during scintillations.Aerospace Engineering and Engineering Mechanic

Assessing the Spoofing Threat: Development of a Portable GPS Civilian Spoofer

A portable civilian GPS spoofer is implemented on a digital signal processor and used to characterize spoofing effects and develop defenses against civilian spoofing. This work is intended to equip GNSS users and receiver manufacturers with authentication methods that are effective against unsophisticated spoofing attacks. The work also serves to refine the civilian spoofing threat assessment by demonstrating the challenges involved in mounting a spoofing attack.Aerospace Engineering and Engineering Mechanic

Business Plan of Healthy Ice Cream Parlor

Bakalářská práce se bude zabývat problematikou podnikatelského záměru. Rozhodování předcházejícímu vytvoření podnikatelského plánu, jako je například volba formy podnikatelského subjektu (OSVČ vs. s.r.o.), formy financování (jaký produkt bude nejvhodnější, popřípadě využití možnosti financování vlastními zdroji). Dále se práce zaměří na možnosti expanze společnosti.The bachelor thesis will deal with the issue of a business plan. Pre-business decision making, such as choosing a form of business entity (self-employed vs. Ltd.), forms of financing (what product will be most appropriate, or use of own-fund finance). In addition, the work will focus on the possibilities of expansion of the company.