Stratigraphic analyses of lacustrine sediments provide powerful tools for reconstructing past environments. The records that result from these analyses are key to understanding present-day climate mechanisms and how the natural environment may respond to anthropogenic climate change in the future. This doctoral dissertation research investigates climate and environmental history at Laguna Saladilla (19° [degrees] 39' N, 71° [degrees] 42' W; ca. 2 masl), a large (220 ha) lake along the north coast of Hispaniola. I reconstructed changes in vegetation and environmental conditions over the mid to late Holocene based on pollen, microscopic charcoal, and diatoms in an 8.51 m sediment core recovered from the lake in 2001. Fieldwork in December 2009 included the use of ground penetrating radar to identify subaqueous deltas that indicate past positions of the Masacre river, which flows into the lake from the Cordillera Central. Laguna Saladilla was deeper and more saline from the base of the sediment profile approximately 8030 cal yr BP to about 3500 cal yr BP. Mangrove (Rhizophora) pollen percentages were highest around 7650 cal yr BP, when mollusk shells in the core suggest marine conditions. The lake became progressively brackish ca. 3500 cal yr BP, followed by a transition ca. 2500 cal yr BP to its current freshwater state. This shift in water chemistry was likely due in part to a change in the position of the Masacre river. Diatoms show that lake levels decreased as evaporation/precipitation ratios increased. Amaranthaceae and other herbs dominated the pollen record under the drier conditions of the last 2500 cal yr BP; pollen of fire-adapted taxa, particularly Pinus, increased in the last 800 years. Patterns of microscopic charcoal influx at Laguna Saladilla over the Holocene are similar to patterns at Lake Miragoane, Haiti and Laguna Tortuguero, Puerto Rico. The changes in fire frequency or extent indicated by these Caribbean charcoal records may be driven by increased winter insolation at ca. 5000 cal yr BP that led to earlier winter drying. Comparing the charcoal record to archeological data and other paleoenvironmental records facilitated the disentangling of changes in climate from anthropogenic impacts.

The Panola Mountain Research Watershed (PMRW) is a 41 ha forested watershed, located 25 km southeast of Atlanta, Georgia. Within that watershed is a 10 ha sub-catchment which contains the headwaters of the watersheds main stream, as well as two outcrops of Panola Granite (Burns et al. 2001). On the hill-slope below the northernmost outcrop, is a 20m long trench that has been excavated down to bedrock, a depth that ranges from 0.5-1.5m. In previous studies (Burns et al., 2001; Freer, et al., 2002), discharge through the overlying soils was measured along the trench in 2m sections across the full length of the trench. In those studies, it was assumed that the underlying bedrock was impermeable. However, Burns et al. (2003) showed that the riparian groundwater downslope from the trenched hillslope site was only 6 to 7 years old. The permeability of the Panola granite in question was proven by a recent Lithium- Bromide line tracer experiment -van Meerveld et al., in review. Due to the levels of bromide in the bedrock measured at the trench, it has become apparent that fluid is being lost to hidden hydraulic pathways, those probably being fractures. The objective of this thesis is to test the viability of using shallow seismic reflection to map out fracture zones at the trenched hillslope site, using GPR and shallow seismic refraction as supplemental techniques to verify the interpretation. Data from two seismic common shot point (CSP) surveys permitted an image of the soil/bedrock interface to be constructed, as well as enabling an acoustic velocity profile to be calculated for the area. This velocity profile is then used with data from five reflection surveys (one seismic and four radar) to create vertical profiles of the subsurface. Although the resulting SSR profile is less than optimum, higher amplitude arrivals related to structure were still able to be detected. From this profile, as well as those from the GPR survey, it can be concluded that the proposed hidden hydraulic pathways due indeed exist, and also that they can be accurately mapped out using the previously mentioned geophysical methods.

Novel microwave transmitter and receiver circuits have been developed for implementing UWB (Ultra-Wideband) impulse radar imaging sensor operating in frequency band 0.2 to 4 GHz. with tunable operating frequency band. The fundamental system design parameters such as the required transmitting pulse power and the pulse duration were estimated for a presumed specific application, the pavement assessment. The designed transmitter is the tunable monocycle pulse generator with tuning capability for the output pulse duration from 450- to 1200- ps, and has relatively high transmitting pulse power from 200 to 400 mW. Tuning of the pulse duration was implemented by novel PIN diode switch configuration and decoupling circuit, and boosting of transmitting pulse power was made possible by using a high power pulse driving circuit and SRD coupling circuit. The synchronous sampling receiver system was designed by using the integrated sampling mixer and two reference clock oscillators placed in the transmitter and receiver respectively for timing control. A novel integrated CSH (Coupled-Slotline Hybrid)sampling mixer has been developed along with the design of the strobe pulse generator appropriate for the impulse radar system. The integrated sampling mixer has unprecedented conversion loss of 2.5 dB for the pulse signal, bandwidth 5.5 GHz, and dynamic range 50 dB. The introduced UWB LNA (Low Noise Amplifier) design operating up to 4 GHz should be useful for weak signal detection applications. The design of the UWB microstrip quasi-horn antenna was optimized for short pulse transmission with respect to the input return loss and the pulse stretching effect. For signal detection in the signal processing stage, the background subtraction technique and B-scan data format were used. A novel signal monitoring technique was introduced in the signal processing to compensate the frequency modulation effect of the reference clock. The test results for the complete system with respect to some sample multi-layer structures shows good receiving pulse waveform with low distortion, enough pulse penetration depth for 13” pavement sample structure, and minimum 1-in of range resolution.

Neste trabalho foi realizado um levantamento GPR 4D em laboratório no qual foi simulado o vazamento de óleo de uma ETD - Estação de Transmissão e Distribuição de Energia Elétrica. Os estudos consistiram em derramar 15 litros de óleo em três experimentos: tanque contendo areia seca, tanque contendo areia úmida mais gradiente hidráulico e tanque contendo areia úmida. Em todos os experimentos o objetivo foi detectar a pluma de contaminação e avaliar a migração desse óleo com o tempo. Os dados GPR 4D foram adquiridos utilizando-se uma antena blindada de 400 MHz modelo SIR-3000 equipamento da GSSI. O monitoramento no tempo de aquisição dos dados variou de 2 minutos até 12 dias. No experimento com o tanque preenchido com areia seca não foi possível determinar a pluma de contaminação devido ao baixo contraste entre as propriedades físicas do meio e a pluma contaminante. No experimento em que o tanque foi preenchido com areia úmida e havia a presença de um gradiente hidráulico, foi possível determinar a migração da pluma de contaminação a partir do 5º dia. Para finalizar, o 3º experimento onde o tanque estava cheio de areia úmida também não foi possível identificar a pluma, devido ao baixo contraste entre as propriedades físicas. Nesta pesquisa também foram realizadas modelagens numéricas 2D utilizando o método FDTD, onde foram simulados os três experimentos, considerando posições intermediárias da pluma de contaminação em função do tempo. Os resultados das modelagens foram concordantes com os resultados obtidos com dados reais e ajudaram a definir o padrão de reflexão da pluma contaminante. Os promissores resultados indicam que a determinação efetiva da pluma contaminante de óleo numa ETD é possível desde o meio que esteja saturado com água. Portanto, para garantir o sucesso das pesquisas GPR para fins de mapeamento e delineamento de plumas de contaminação em ETDs recomenda-se que a aquisição dos dados seja feita após um período de chuvas. / In this work a 4D GPR survey was accomplished in a laboratory in which a oil leak from a ETD Estação de Transmissão e Distribuição of electric energy was simulated. The studies consisted in an oil spill (15 liters) in three different experiments: i) tank containing dry sand, ii) tank containing wet sand with a hydraulic gradient and iii) tank containing wet sand. In all experiments the objective was detect the contamination plume and evaluate the migration of the oil with the time. The 4D GPR data was acquired using a shielded antenna of 400 MHz model SIR-3000 of the GSSI equipment. The time monitoring of the data acquisition ranged from 2 minutes up to 12 days. In the experiment-1 with the tank filled with dry sand wasnt possible to determine the plume contamination due to the low contrast of the physical properties between the environment and the plume. In the experiment-2 where the tank filled with the dry sand in the presence of a hydraulic gradient, was possible to determine the migration of the plume from the fifth day. Finally, the experiment-3 where the tank was filled with wet sand wasnt possible to identify the plume, due to the low contrast between the physical properties. This research also conducted 2D numerical modeling using the FDTD method, where the three experiments were simulated, considering intermediary positions of the contamination plume with respect with time. The results of the modeling were consistent with the results obtained with real data and helped to define a pattern of reflection of the contamination plume. The promising results indicate that the effective determination of the contaminating plume of oil in an ETD is possible provided that the environment be saturated with water. Therefore, to guarantee the success of researches with GPR for mapping and delineation of contamination plumes in ETDs its recommended that the data acquisition be realized in the rainy season.

Ground Penetrating Radar (GPR) methods have been used to evaluate the presence, extent, and spatial variability of hydrophobic soils in Southern California Watersheds. It has been shown that high frequency ground penetrating radar equipment, under certain conditions, has the ability to determine the presence, depth, and persistence of post fire hydrophobic soils. As part of this study an extensive investigation was undertaken to not only evaluate the capability of this approach but also to understand under what conditions the method can be applied successfully and what are the limitations of the approach. The investigation includes use of computer simulations and modeling, laboratory investigations in sand boxes with native soils, and multiple field trials spanning a five year time period. Of particular significance is the finding that using GPR it is possible to: locate the interface between the uppermost burnt soil layer, and soil horizons below; quantify the depth at which the hydrophobic layer forms; and quantify the spatial extent of the layer. As part of this study best practice methods for both field and lab experimentation have also been developed and are presented in the body of the thesis. Based on this study it is concluded that the use of GPR can provide a much more accurate and comprehensive method of evaluating the nature of hydrophobic layers in such environments than the current point specific manual methods. As a result the use of GPR has significantly advanced our capacity to assess the potential for increased erosion and the generation of debris flows in such environments after rainfall events.

Ground penetrating radar (GPR) has been used as a railway substructure investigation tool since the late 1990’s and has seen significant development since then. To use GPR as a more effective tool for substructure investigation, a GPR substructure characterization model was developed. This dissertation provides a detailed description of railway track components, track geometry, soil properties and classification and substructure design. The historical background of GPR is discussed together with GPR principles, basic GPR equations, hardware and accessories as well as GPR data collection, processing and interpretation. Other in situ investigation techniques namely the dynamic cone penetrometer (DCP), light weight deflectometer (LWD) , Pencel pressuremeter, surface wave testing, remote video monitoring (RVM), multi-depth deflectometers (MDD) and continuous track modulus measurement techniques are also discussed. A comparison between the different track investigation techniques was also done, with reference to sample rate, cost, effectiveness and value. Two sites in South Africa were selected for the investigation, one with good substructure conditions used for heavy haul coal export close to Vryheid (KN test section) and the other a general freight line with poor substructure conditions near Rustenburg (NT test section). These two sites were selected to develop a GPR substructure characterization model as they provided conditions ranging from poor to very good. This was supported by the analysis of the in situ soil sampling and testing. The calculation of the track substructure modulus from RVM deflection measurements showed three times higher values for the KN test section compared to the NT test section. The subballast and subgrade thickness, the GPR ballast fouling (GBF) index as well as the GPR moisture condition index was used for the classification ranges used in the model. The subballast and subgrade layer roughness values were calculated and used for the substructure classification. The GBF index and the GPR moisture condition roughness were used for the GPR fouling index classification. The GPR deliverables were divided into four classes (i.e. very good, good, moderate and poor). The evaluation of the characterization model showed that a traditional in situ investigation will cost approximately 3.7 times more than that of a GPR investigation. It would also take two thirds of the time to complete the GPR investigation compared to the traditional in situ investigation. The study showed that GPR can be used to develop a substructure characterization model and that it would be more cost effective and efficient than traditional in situ investigation techniques. GPR surveys provide continuous measurements of the track structure condition and can therefore provide a continuous classification unlike the discreet and fragmented nature of in situ investigations. However, in situ tests can be done at certain intervals within the GPR survey or at point where the GPR classification is not clear. The best solution for railway track characterization can therefore be obtained by using GPR and in situ classification in combination. / Dissertation (MEng)--University of Pretoria, 2012. / Civil Engineering / unrestricted

A lot of features that need to be scanned underground should not be disturbed, from waterlines to unmarked graves. A non-invasive way of probing underground is Ground-Penetrating Radar (GPR). GPR finds differences in materials with radar waves. However, GPR is human-operated and its position is generally determined with a GPS. In some cases, the presence of a human operator can be dangerous, and in other cases, the GPS is not reliable (i.e. mines, glaciers). Therefore there are situations where an autonomous and non-GPS-reliant solution is preferable. The current state of the autonomous GPR system targeted in this work has a non-intuitive GUI that requires an experienced hand to operate. I present an updated hardware and software platform with an intuitive GUI. This updated autonomous system continuously builds a map of its surroundings with Simultaneous Mapping And Localization (SLAM). SLAM localizes itself within the map through sensor-fused position estimates. After the survey is completed the positions are saved and integrated with radar data to be visualized. Robot Operating System 2 (ROS2) is the software I used that allows communications between hardware components, software systems, and the GUI. The new hardware package uses only one source of power and is built using quick connectors that allow for quick removal from the GPR platform. This system allows for intuitive autonomous survey planning and execution in any field paired with a simple way of visualizing data.

Legio is the base of the Roman II Triana and the VI Ferrata Legion, occupied from the early 2nd century to the early 4th century CE. It is the first of its kind to be excavated in the Eastern Roman Empire. Today the site sprawls beneath 30 hectares of pasture with slopes up to 15 degrees. Rapid, dense ground penetrating radar (GPR) survey with an antenna array would be ideal, but so far logistically impractical. The survey has proceeded since 2013 with a single 400 MHz antenna using parallel transects 0.5m apart for 5.85 ha to date. Like most Roman bases, Legio includes an extensive network of buildings and streets enclosed by rectangular fortifications. Unlike most Roman bases, however, it was constructed on a hillside with architectural components built by a combination of bedrock incision and above-ground construction. In addition, much of the site’s stonework has been robbed. These aspects demand topographic correction and interpretation using reflection profiles, depth slices, and 3D models. This paper presents data processing and results for the principia (central headquarters). Previous investigations were conducted at Legio and surrounding area by Tel Aviv University from 1998 to 2010. GPR and excavations since 2013 have been conducted as part of the Jezreel Valley Regional Project (JVRP)in association with the W.F. Albright Institute of Archaeological Research.

Bioturbation in supratidal carbonate substrates has only recently received attention from ichnologists, relying primarily on traditional ground-based techniques. This study is the first high-resolution geophysical investigation of three decapod species inhabiting adjacent coastal biotopes on San Salvador Island. Extensive (>2 km) 800 MHz georadar surveys captured a diverse suite of >120 burrows of ghost (Ocypode quadrata), blackback (Gecarcinus lateralis) and blue (Cardisoma guanhumi) land crabs. Site-specific post-processing protocols were used to establish characteristic attributes that distinguish unfilled burrows from other discordant anomalies based on signal polarity structure. Variably oriented 2D and quasi-3D (~0.75-1.25 wavelength line separation) images allow the diagnostic signature of G. lateralis burrows to be distinguished from those of O. quadrata based on: 1) higher density of point-source diffractions (0.9-1.9/m vs. 0.01-0.06/m) and 2) shallower inclination angle (21-46° vs. >60°). C. guanhumi burrows are differentiated by: 1) larger diameter; 2) presence of an end chamber (where the radar signal is not attenuated by saline groundwater); 3) low electromagnetic signal velocity (~9 cm/ns vs. ~11 cm/ns) in organic-rich muddy substrate and 4) rapid signal decay. The migrated inclination angle (a) and the effective range (t0; time window of strongest reflectors) offer the best combination that differentiates between the three end-member structures and matrix properties. This study establishes GPR as a viable non-invasive subsurface imaging technique, with potential implications for: 1) identification of shifting ichnocoenoses, as exemplified by intense hurricane impacts (2015/2016); 2) recognition and mapping of similar biogenic structures in buried or lithified carbonates and, 3) quantification of a near-surface ichnofabric index and the dual porosity/permeability structure of prospective hydrocarbon reservoirs. Furthermore, the basic attributes of subsurface visualization can be readily extended to other mesoscale biogenic structures in evaporite and siliciclastic media. / Geology

This paper contains geophysical analysis of the largest town square in Sigtuna, Sweden. The studied area is approximately 736 m2. The purpose of the study was to search for early medieval house remnants and to possibly find structures matching those found during excavations in other parts of the town. The hypothesis is that the town of Sigtuna was planned and that the yards of the town were put out in a special pattern following the main street, which is the same as today. During the day of the geophysical prospection the weather conditions were not optimal. A lot of water at the surface disturbed the instrument and gave a blurred image. It turned out that a lot of contemporary pipes and a large traffic island from the 1930s covered the area. Archaeological structures could only be seen in smaller areas in between later structures. Vague oblong structures could be seen, as well as a distinct smaller square on the eastern part of the area. A large rectangle close to the main street was also observed. None of these structures could be seen in modern maps or photographs and are therefore marked as something that could be of archaeological interest. Some of the structures that were noted were probably part of the original medieval town plan, as judged by their size and location.