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USGS2019

Regional hydraulic geometry characteristics of stream channels in the Ouachita Mountains of Arkansas

Many stream channel infrastructure, habitat, and restoration projects are being undertaken on small streams throughout Arkansas by various Federal, State, and local agencies and by private organizations and businesses with limited data on local geomorphology and streamflow relations. Equations are needed that relate drainage area above stable stream reaches and the associated basin characteristics to bankfull streamflow and the associated channel dimensions. These equations, along with streambed material particle information, provide information that can improve stream channel projects. The U.S. Geological Survey and the Arkansas Natural Resources Commission in cooperation with the U.S. Army Corps of Engineers, Little Rock District, undertook a study to develop these equations for streams in the Ouachita Mountains of Arkansas. Seventeen streamgages operated by the U.S. Geological Survey, located on streams in the Ouachita Mountains, were selected for analysis. Regional hydraulic geometry curves that express the mathematical relation between the bankfull channel dimensions (cross-sectional area, top width, mean depth, and streamflow) and the contributing drainage areas were developed. Streambed material measurements were collected to develop descriptive statistics of the streambed particle-size distributions and percentages of substrate type at each study site. Stream reaches at each study site were classified to the Rosgen level II stream type based on the average of stream channel metrics collected from site cross sections and profiles. Of the 17 selected Ouachita Mountain stream reaches, 6 were classified as B stream types, and 11 were classified as C stream types. The B stream types have infrequently spaced pools; very stable plan forms, profiles, and banks; and narrow, gently sloping valleys, where bank vegetation is a moderate component of stability. The C stream types are meandering, point bar, riffle-pool channels associated with broad valleys having well-defined flood plains and terraces composed of alluvial soils, where bank vegetation is typically a high component of stability.

Arkansas↗

USGS1989

Conversion and comparison of the mathematical, three-dimensional, finite-difference, ground-water flow model to the modular, three-dimensional, finite-difference, ground-water flow model for the Tesuque aquifer system in northern New Mexico

The three-dimensional finite-difference groundwater model (using a mathematical groundwater flow code) of the Tesuque aquifer system in northern New Mexico was converted to run using the U.S. Geological Survey 's modular groundwater flow code. Results from the final versions of the predevelopment and 1947 to 2080 transient simulations of the two models are compared. A correlation coefficient of 0.9905 was obtained for the match in block-by-block head-dependent fluxes for predevelopment conditions. There are, however, significant differences in at least two specific cases. In the first case, a difference is associated with the net loss from the Pojoaque River and its tributaries to the aquifer. The net loss by the river is given as 1.134 cu ft/sec using the original groundwater model, which is 38.1% less than the net loss by the river of 1.8319 cu ft/sec computed in this study. In the second case, the large difference is computed for the transient decline in the hydraulic head of a model block near Tesuque Pueblo. The hydraulic-head decline by 2080 is, using the original model, 249 ft, which is 14.7% less than the hydraulic head of 292 ft computed by this study. In general, the differences between the two sets of results are not large enough to lead to different conclusions regarding the behavior of the system at steady state or when pumped. (USGS)

Open-File Report↗

USGS2003

The saturated zone at Yucca Mountain: An overview of the characterization and assessment of the saturated zone as a barrier to potential radionuclide migration

The US Department of Energy is pursuing Yucca Mountain, Nevada, for the development of a geologic repository for the disposal of spent nuclear fuel and high-level radioactive waste, if the repository is able to meet applicable radiation protection standards established by the US Nuclear Regulatory Commission and the US Environmental Protection Agency (EPA). Effective performance of such a repository would rely on a number of natural and engineered barriers to isolate radioactive waste from the accessible environment. Groundwater beneath Yucca Mountain is the primary medium through which most radionuclides might move away from the potential repository. The saturated zone (SZ) system is expected to act as a natural barrier to this possible movement of radionuclides both by delaying their transport and by reducing their concentration before they reach the accessible environment. Information obtained from Yucca Mountain Site Characterization Project activities is used to estimate groundwater flow rates through the site-scale SZ flow and transport model area and to constrain general conceptual models of groundwater flow in the site-scale area. The site-scale conceptual model is a synthesis of what is known about flow and transport processes at the scale required for total system performance assessment of the site. This knowledge builds on and is consistent with knowledge that has accumulated at the regional scale but is more detailed because more data are available at the site-scale level. The mathematical basis of the site-scale model and the associated numerical approaches are designed to assist in quantifying the uncertainty in the permeability of rocks in the geologic framework model and to represent accurately the flow and transport processes included in the site-scale conceptual model. Confidence in the results of the mathematical model was obtained by comparing calculated to observed hydraulic heads, estimated to measured permeabilities, and lateral flow rates calculated by the site-scale model to those calculated by the regional-scale flow model. In addition, it was confirmed that the flow paths leaving the region of the potential repository are consistent with those inferred from gradients of measured head and those independently inferred from water-chemistry data. The general approach of the site-scale SZ flow and transport model analysis is to calculate unit breakthrough curves for radionuclides at the interface between the SZ and the biosphere using the three-dimensional site-scale SZ flow and transport model. Uncertainties are explicitly incorporated into the site-scale SZ flow and transport abstractions through key parameters and conceptual models. ?? 2002 Elsevier Science B.V. All rights reserved.

Journal of Contaminant Hydrology↗

USGS1983

Geophysical methods for locating abandoned wells

A preliminary study of the feasibility of using geophysical exploration methods to locate abandoned wells containing steel casing indicated that magnetic methods promise to be effective and that some electrical techniques might be useful as auxiliary methods. Ground magnetic measurements made in the vicinity of several known cased wells yielded total field anomalies with peak values ranging from about 1,500 to 6,000 gammas. The anomalies measured on the ground are very narrow and, considering noise due to other cultural and geologic sources, a line spacing on the order of 50 feet (15.2 m) would be necessary to locate all casings in the test area. The mathematical model used to represent a casing was a set of magnetic pole pairs. By use of a non-linear least squares curve fitting (inversion) program, model parameters which characterize each test casing were determined. The position and strength of the uppermost pole was usually well resolved. The parameters of lower poles were not as well resolved but it appears that the results are adequate for predicting the anomalies which would be observed at aircraft altitudes. Modeling based on the parameters determined from the ground data indicates that all of the test casings could be detected by airborne measurements made at heights of 150 to 200 feet (45.7-61.0 m) above the ground, provided lines spaced as closely as 330 feet (100 m) were used and provided noise due to other cultural and geologic sources is not very large. Given the noise levels of currently available equipment and assuming very low magnetic gradients due to geologic sources, the detection range for total field measurements is greater than that for measurements of the horizontal or vertical gradient of the total intensity. Electrical self-potential anomalies were found to be associated with most of the casings where measurements were made. However, the anomalies tend to be very narrow and, in several cases, they are comparable in magnitude to other small anomalies which are not directly associated with casings. Measurements made with a terrain conductivity meter and slingram system were negative. However, from other work it is known that electrical resistivity and induced polarization measurements can be influenced significantly by the presence of a casing. It is concluded that detailed ground magnetic surveys would be effective in locating casings within relatively small areas. It would be very costly to cover large areas with ground surveys but it appears that airborne surveys may be a cost-effective means of locating wells when the search area is on the order of a few square miles or more. Also, airborne methods could be used in some areas where access to the area on the ground is difficult or impossible.

Open-File Report↗

USGS2025

lasertram: A Python library for time resolved analysis of laser ablation inductively coupled plasma mass spectrometry data

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) data has a wide variety of uses in the geosciences for in-situ chemical analysis of complex natural materials. Improvements to instrument capabilities and operating software have drastically reduced the time required to generate large volumes of data relative to previous methodologies. Raw data from LA-ICP-MS, however, is in counts per unit time (typically counts per second), not elemental concentrations and converting these count ratesto concentrations requires additional processing. For complex materials where the ablated volume may contain a range of material compositions, a moderate amount of user input is also required if appropriate concentrations are to be accurately calculated. In geologic materials such as glasses and minerals that potentially have numerous heterogeneities (e.g., microlites or other inclusions) within them, this is typically determiningwhether the total ablation signal should be filtered to remove these heterogeneities. This necessitates that the LA-ICP-MS data processing pipeline is one that is not automated, but is also designed to enable rapid and efficient processing of large volumes of data. Here we introduce , a Python library for the time resolved analysis of LA-ICP-MS data. We outline its mathematical theory, code structure, and provide an example of how it can be used to provide the time resolved analysis necessitated by LA-ICP-MS data of complex geologic materials. Throughout the pipeline we show how metadata and data are incrementally added to the objects created such that virtually any aspect of an experiment may be interrogated and its quality assessed. We also show, that when combined with other Python libraries for building graphical user interfaces, it can be utilized outside of a pure scripting environment. can be found at https://doi.org/10.5066/P1DZUR3Z

Applied Computing and Geosciences↗

USGS2020

Landslide disparities, flume discoveries, and Oso despair

Landslide dynamics is the branch of science that seeks to understand the motion of landslides by applying Newton's laws. This memoir focusses on a 40‐year effort to understand motion of highly mobile—and highly lethal—landslides such as debris avalanches and debris flows. A major component of this work entailed development and operation of the U.S. Geological Survey debris flow flume, a unique, large‐scale experimental facility in Oregon. Experiments there yielded new insights that informed development of mathematical models that were aimed not only at explaining landslide dynamics but also at evaluating landslide and debris flow hazards. The most sophisticated of these models, called D‐Claw, found its first practical application during investigations of the 2014 Oso, Washington, landslide disaster. That event provided indelible lessons about the utility and sociology of science in the real world.

Washington↗

USGS2012

Analytical resource assessment method for continuous (unconventional) oil and gas accumulations - The "ACCESS" Method

The U.S. Geological Survey (USGS) periodically assesses petroleum resources of areas within the United States and the world. The purpose of this report is to explain the development of an analytic probabilistic method and spreadsheet software system called Analytic Cell-Based Continuous Energy Spreadsheet System (ACCESS). The ACCESS method is based upon mathematical equations derived from probability theory. The ACCESS spreadsheet can be used to calculate estimates of the undeveloped oil, gas, and NGL (natural gas liquids) resources in a continuous-type assessment unit. An assessment unit is a mappable volume of rock in a total petroleum system. In this report, the geologic assessment model is defined first, the analytic probabilistic method is described second, and the spreadsheet ACCESS is described third. In this revised version of Open-File Report 00-044 , the text has been updated to reflect modifications that were made to the ACCESS program. Two versions of the program are added as appendixes.

Open-File Report↗

USGS1968

On the maintenance of anomalous fluid pressures: II. Source layer at depth

Physico-chemical mechanisms have been suggested to account for anomalous fluid pressures in the geologic environment which require a fluid source at depth. The persistence of anomalous pressure is a problem that involves nonsteady fluid flow. The hydrodynamics and particular boundary conditions control the time rate of pressure change and its maintenance. A series of mathematical solutions germane to the maintenance of anomalous pressure caused by the injection of fluids into the system from a source layer are presented. The phase change, gypsum to anhydrite plus water, is used as an example of a fluid source at depth. The thermodynamics of the gypsum-dehydration reaction indicates that conversion will probably occur at shallow depths and produce fluid at a constant rate. The dehydration of montmorillonite will also produce fluids at a constant rate under geologic conditions where the reaction can occur. If horizons of material of low permeability are missing or scarce, it is doubtful that anomalous pore pressures can be maintained for more than a geologic instant. The creation and continuation of anomalous pressure depend largely upon the hydraulic conductivity and, to a lesser extent, upon the specific storage of clay layers within the system. © 1968, The Geological Society of America, Inc.

Geological Society of America Bulletin↗

USGS2023

Calibration of imperfect geophysical models by multiple satellite interferograms with measurement bias

Model calibration consists of using experimental or field data to estimate the unknown parameters of a mathematical model. The presence of model discrepancy and measurement bias in the data complicates this task. Satellite interferograms, for instance, are widely used for calibrating geophysical models in geological hazard quantification. In this work, we used satellite interferograms to relate ground deformation observations to the properties of the magma chamber at K i¯lauea Volcano in Hawai‘i. We derived closed-form marginal likelihoods and implemented posterior sampling procedures that simultaneously estimate the model discrepancy of physical models, and the measurement bias from the atmospheric error in satellite interferograms. We found that model calibration by aggregating multiple interferograms and downsampling the pixels in the interferograms can reduce the computation complexity compared to calibration approaches based on multiple data sets. The conditions that lead to no loss of information from data aggregation and downsampling are studied. Simulation illustrates that both discrepancy and measurement bias can be estimated, and real applications demonstrate that modeling both effects helps obtain a reliable estimation of a physical model’s unobserved parameters and enhance its predictive accuracy. We implement the computational tools in the RobustCalibration package available on CRAN.

Technometrics↗

USGS1951

Radon in the helium-bearing natural gas of the Texas panhandle

The known quantity of helium in the Texas Panhandle gas reservoir is greater than could be explained by assuming normal geologic conditions. Radon content of the gas varies between about 10 and 250 micromicrocuries per liter (S. T. P.), and the more highly radioactive wells are clustered in several groups. Mathematical analysis indicates that the larger concentrations of radon could not be derived from rocks of normal radioactivity.

Texas↗

USGS1961

Graphic and algebraic solutions of the discordant lead-uranium age problem

Uranium-bearing minerals that give lead-uranium and lead—lead ages that are essentially in agreement, i.e. concordant, generally are considered to have had a relatively simple geologic history and to have been unaltered since their deposition. The concordant ages obtained on such materials are, therefore, assumed to approach closely the actual age of the minerals. Many uranium-bearing samples, particularly uranium ores, give the following discordant age sequences; Pb 206 U 238 < Pb 207 U 235 ⪡ Pb 207 Pb 206 "> Pb 206 U 238 <Pb 207 U 235 ⪡Pb 207 Pb 206 or, less frequently, Pb 207 Pb 206 ⪡ Pb 207 U 235 < Pb 206 U 238 "> Pb 207 Pb 206 ⪡Pb 207 U 235 <Pb 206 U 238 . These discordant age sequences have been attributed most often to uncertainties in the common lead correction, selective loss of radio-active daughter products, loss or gain of lead or uranium, or contamination by an older generation of radiogenic lead. The evaluation of discordant lead isotope age data may be separated into two operations. The first operation, with which this paper is concerned, is mechanical in nature and involves the calculation of the different possible concordant ages corresponding to the various processes assumed to have produced the discordant ages. The second operation is more difficult to define and requires, in part, some personal judgement. It includes a synthesis of the possible concordant age solutions with other independent geologic and isotopic evidence. The concordant age ultimately chosen as most acceptable should be consistent not only with the known events in the geologic history of the area, the age relations of the enclosing rocks, and the mineralogic and paragenetic evidence, but also with other independent age measurements and the isotopic data obtained on the lead in related or associated non-radioactive minerals. The calculation of the possible concordant ages from discordant age data has been greatly simplified by Wetherill's graphical method of plotting the mole ratios of radiogenic Pb 206 U 238 "> Pb 206 U 238 ( N 206 N 238 "> N 206 N 238 ) vs. radiogenic Pb 207 U 235 "> Pb 207 U 235 ( N 207 N 235 "> N 207 N 235 ) after correcting for the contaminating common Pb 206 and Pb 207 . The linear relationships noted in this graphical procedure have been extended to plots of the mole ratios of total Pb 206 U 238 "> Pb 206 U 238 ( t N 206 N 238 "> t N 206 N 238 ) vs. total Pb 207 U 235 "> Pb 207 U 235 ( t N 207 N 235 "> t N 207 N 235 ). This modification permits the calculation of concordant ages for unaltered samples using only the Pb 207 Pb 206 "> Pb 207 Pb 206 ratio of the contaminating common lead. If isotopic data are available for two samples of the same age, x and y , from the same or related deposits or outcrops, graphs of the normalized difference ratios [ ( N 206 N 204 )x − ( N 206 N 204 )y ( N 238 N 204 )x −( N 238 N 204 )y ] vs. [ ( N 207 N 204 )x − ( N 207 N 204 )y ( N 235 N 204 )x −( N 235 N 204 )y ] "> [(N 206 N 204 )x − (N 206 N 204 )y(N 238 N 204 )x −(N 238 N 204 )y] vs. [(N 207 N 204 )x − (N 207 N 204 )y(N 235 N 204 )x −(N 235 N 204 )y] can give concordant ages corrected for unknown amounts of a common lead with an unknown Pb 207 / Pb 206 ratio. (If thorium is absent the difference ratios may be normalized with the more abundant index isotope, Pb 208 .) Similar plots of tho normalized, difference ratios for three genetically related samples ( x − y ) and( x − z ), will give concordant ages corrected, in addition, for either one unknown period of past alteration or initial contamination by an older generation of radiogenic lead of unknown Pb 207 /Pb 206 ratio. Practical numerical solutions for many of tho concordant age calculations are not currently available. However, the algebraic equivalents of these new graphical methods give equations which may be programmed for computing machines. For geologically probable parameters the equations of higher order have two positive real roots that rapidly converge on the exact concordant ages corrected for original radiogenic lead and for loss or gain of lead or uranium. Modifications of these general age equations expanded only to the second degree have been derived for use with desk calculators. These graphical and algebraic methods clearly suggest both the type and minimum number of samples necessary for adequate mathematical analysis of discordant lead isotope age data. This mathematical treatment also makes it clear that discordant lead isotope data alone cannot provide the basis for the choice of one of the possible concordant age solutions. The new equations, in particular, provide an incentive to improve our physical constants, analytical techniques and sampling methods in order that we may derive all of the useful geologic information that is available in a comprehensive lead isotope age study.

Geochimica et Cosmochimica Acta↗

USGS1976

Landslides - Cause and effect

Landslides can cause seismic disturbances; landslides can also result from seismic disturbances, and earthquake-induced slides have caused loss of life in many countries. Slides can cause disastrous flooding, particularly when landslide dams across streams are breached, and flooding may trigger slides. Slope movement in general is a major process of the geologic environment that places constraints on engineering development. In order to understand and foresee both the causes and effects of slope movement, studies must be made on a regional scale, at individual sites, and in the laboratory. Areal studies — some embracing entire countries — have shown that certain geologic conditions on slopes facilitate landsliding; these conditions include intensely sheared rocks; poorly consolidated, fine-grained clastic rocks; hard fractured rocks underlain by less resistant rocks; or loose accumulations of fine-grained surface debris. Field investigations as well as mathematical- and physical-model studies are increasing our understanding of the mechanism of slope movement in fractured rock, and assist in arriving at practical solutions to landslide problems related to all kinds of land development for human use. Progressive failure of slopes has been studied in both soil and rock mechanics. New procedures have been developed to evaluate earthquake response of embankments and slopes. The finite element method of analysis is being extensively used in the calculation of slope stability in rock broken by joints, faults, and other discontinuities.

Bulletin of the International Association of Engin↗

USGS2020

Dimensional effects of inter-phase mass transfer on attenuation of structurally trapped gaseous carbon dioxide in shallow aquifers

Based on experimental evidence and using mathematical modeling, inter-phase mass transfer processes of CO 2 exsolving from and dissolving into water in heterogeneous porous media are investigated under two fundamentally different flow conditions: in a quasi one dimensional vertical column and in a two-dimensional tank with a lateral background water flow, both at laboratory scale. In both cases, the CO 2 dissolved in water under a given overpressure is injected for a certain period at the bottom of the tank, exsolves, and migrates upwards. A layer of fine sand is present in the tanks designed to mimic geological scenarios of accumulation and trapping of exsolved CO 2 in shallow aquifers. Then, clean water is injected and the accumulated CO 2 is dissolved back into the flowing water. The study aims to point out the differences in the mass transfer processes between the quasi-1D and 2D cases using a mathematical model of two-phase compositional flow in heterogeneous porous media calibrated to the experimental datasets, and expose strategies that should be explored in future research. Additionally, temperature variations observed during the 2D experiments allow for analysis of isothermal versus non-isothermal effects on the processes of multiphase CO 2 evolution. The mathematical model is discretized and solved using the mixed hybrid finite element method in 2D that allows for the simulation of both advection- and diffusion-dominated processes accurately.

Journal of Computational Physics↗

USGS2006

Model aids planners in predicting rising ground-water levels in San Bernardino, California

The city of San Bernardino is in a semiarid inland valley about 60 miles (100 kilometers) east of Los Angeles. The southern part of the city is traversed by the San Jacinto fault. Adjacent to the upgradient (northeast) side of the fault is a 10 square mile (26 square kilometers) area which contains a zone in the alluvial ground‐water basin that formerly was under artesian pressure and consisted of swampy lands with a history of flowing wells, springs, and ground‐water discharge to Warm Creek. Since about 1945, water levels have declined more than 100 feet (30 meters), and the swampy lands have dried up and are now highly urbanized. Basin replenishment by artificial recharge of imported northern California water at the base of the San Bernardino Mountains may cause ground‐water levels to rise again in the area that was formerly swampy land. If this should happen, building foundations and basements could be subjected to structural damage and flooding by renewed flowing of unplugged artesian wells. The U.S. Geological Survey, in cooperation with the San Bernardino Valley Municipal Water District, is developing a two‐layer digital model to aid in predicting the rate and extent of the rise in water levels. The solution to the mathematical equations used in the model was approximated numerically by the Galerkin finite‐element method. The water district desires to evaluate water management alternatives, such as varying location, distribution, amounts of recharge, and pumping centers, to avoid excessive water level rises that could indicate an overfilling of the basin and could cause damage.

California↗

USGS2026

Uncertainty quantification of geologic energy storage in depleted gas reservoirs using material balance equations embedded in a hierarchical errors-in-variables model

The storage potential for gas in geologic settings, such as depleted hydrocarbon reservoirs and solution-mined salt caverns, is becoming salient to future energy infrastructure planning. Technologies such as carbon capture, utilization, and storage, carbon dioxide-enhanced oil recovery, and natural gas and hydrogen storage help meet growing energy demands, reduce carbon emissions to meet climate goals, and provide energy security amid geopolitical uncertainties. Therefore, estimates of underground gas storage capacity could be useful for efficiently navigating the energy transitions. Material balance is a fundamental method in reservoir engineering for estimating original gas in place and potential storage capacity at the scale necessary for national assessments of subsurface pore space resources. However, the deterministic method cannot accommodate multiple data sources or quantify uncertainty in predictions. In this study, a method that embeds material balance equations within a hierarchical errors-in-variables model is proposed which allows the estimation of the distributions of reservoir properties needed for assessments. Uncertainties associated with these reservoir properties have traditionally been expert-elicited, whereas the uncertainty estimates from the proposed models are data-driven. Capacity and uncertainty estimates can be used in a probabilistic resource assessment, supplementing information traditionally used by assessors or even replacing this expert elicitation step when data are unavailable. Various regression models are compared in a case study of the Michigan Basin, a large contributor to the United States’ current natural gas storage capacity. In particular, errors-in-variables models help ameliorate regression dilution and can quantify uncertainty in predictions of pressure in addition to storage capacity. Overfitting is addressed by quantifying generalization error and model averaging in simple and stratified cross-validation against reported working gas capacity, representing the varying quality and quantity of available data. Incorporating a statistical framework into existing numerical methods in reservoir engineering can improve the quality of estimation, and in particular, this method brings rigor to uncertainty quantification as part of a larger effort by the U.S. Geological Survey to assess domestic energy gas storage resources in depleted hydrocarbon reservoirs.

Mathematical Geosciences↗

USGS1988

Hydrogeology of the Great Basin region of Nevada, Utah, and adjacent states

This atlas is a product of the Great Basin Regional Aquifer-System Analysis (RASA), a study that began in 1981. The study is part of a U.S. Geological Survey program for evaluating regional aquifer systems nationwide. A regional aquifer system is defined as “an areally extensive set of aquifers which are linked in some way, such as hydraulically or economically” (Harrill and others, 1983, p. 2). The purpose of the Great Basin RASA is to evaluate aquifer system in the Great Basin by developing a better understanding of recharge and discharge processes, delineating individual ground-water flow systems, and developing mathematical models of representative flow systems. Harrill and others (1983) provide a more complete background of both the national RASA program and the Great Basin RASA. The purpose of this atlas is to delineate and describe the major hydrogeologic units in the Great Basin region and to identify those units that (1) constitute regional aquifers or (2) act as barriers to the movement of ground water. The scope of this atlas, however, is limited to a brief geologic overview of the Great Basin: lithology and areal extent of units, major structural features, and influence of tectonic events. In addition, the water-bearing characteristics of each unit are briefly summarized. This atlas is Chapter A of the three-part Hydrologic Atlas series. Chapter B shows ground-water levels in the Great Basin region, and Chapter C shows inferred directions of ground-water flow and individual flow systems.

Nevada, Utah↗

USGS1974

Unique cartographic characteristics of ERTS

The ERTS television sensing system has unique cartographic advantages over aircraft and satellite film systems. These are longer life combined with greater coverage, transmission of data in near real time, orthogonality, excellent geometric precision for planimetric mapping, suitability for automation (because of the basically continuous image on a mathematically definable map projection), radiometric fidelity, and the extension of sensing capability to near-infrared wavelengths.

Journal of Research of the U.S. Geological Survey↗

USGS2000

Using an analytical geometry method to improve tiltmeter data presentation

The tiltmeter is a useful tool for geologic and geotechnical applications. To obtain full benefit from the tiltmeter, easy and accurate data presentations should be used. Unfortunately, the most commonly used method for tilt data reduction now may yield inaccurate and low-resolution results. This article describes a simple, accurate, and high-resolution approach developed at the Illinois State Geological Survey for data reduction and presentation. The orientation of tiltplates is determined first by using a trigonometric relationship, followed by a matrix transformation, to obtain the true amount of rotation change of the tiltplate at any given time. The mathematical derivations used for the determination and transformation are then coded into an integrated PC application by adapting the capabilities of commercial spreadsheet, database, and graphics software. Examples of data presentation from tiltmeter applications in studies of landfill covers, characterizations of mine subsidence, and investigations of slope stability are also discussed.

Environmental & Engineering Geoscience↗