Varying Data Quality Research Articles

Integrated Storage and Querying of Spatially Varying Data Quality Information in a Relational Spatial Database

AbstractThis article investigates a new, integrated technique for storing and retrieving spatially varying data quality information in a relational spatial database. Rather than storing global data quality statements, the system enables data quality information to be referenced to a spatial framework, individual spatial objects, or even parts of spatial objects. The integrated model, called as RDBMS for Spatial Variation in Quality (RSVQ), allows flexible storage of spatially varying data quality information, and seamless querying irrespective of the underlying storage model. RSVQ is founded on a formal model of relational databases, defining a new derived, polymorphic query operator to join quality data with spatial data. The operator is implemented in an extension to SQL as a new WITHQUALITY keyword. A performance evaluation of RSVQ was conducted, using an Oracle Spatial database and a case study of cadastral data for parts of Victoria, Australia. The results of this evaluation demonstrated that the system is practical and efficient for a wide range of queries, as well as indicating the performance trade‐offs associated with the different data quality storage models. Using the integrated RSVQ approach provides the potential for a single, consistent, database engine for a wide range of existing and proposed spatial data quality management systems.

Use of satellite telemetry on small-bodied waterfowl in Australia

The nomadic or dispersive movements of many Australian waterfowl in response to irregular environmental cues make satellite telemetry studies the only means by which these long-distance movements can be tracked in real time. Unlike some large-bodied soaring species, attaching satellite transmitters to small-bodied waterfowl (<1 kg) is not straightforward because ducks have high wing loadings and need to maintain active flapping to stay aloft. In the present paper, we detail one harness design and attachment method that enabled us to track grey teal (Anas gracilis) for up to 879 days. In addition, we detail rates of data loss, changes in data quality over time and variation in data quality from solar-powered satellite-tags deployed on ducks in Australia and Papua New Guinea. Up to 68% of all locational fixes have a nominal accuracy of less than 1 km, and satellite-tags deployed on wild birds can provide up to 22 location fixes per day and store enough energy during the day to run continuously throughout the night.

Determination of total ice volume and ice-thickness distribution of two glaciers in the Hohe Tauern region, Eastern Alps, from GPR data

AbstractGlobal warming is causing an apparent rapid retreat of many glaciers worldwide. In addition to mass-balance investigation, the determination and monitoring of total glacial ice volume and ice-thickness distribution are important parameters for understanding the interactions between climate and the complex glacier system. Because of spatially irregular and sparse datasets, scaling of volume and ice-thickness distribution is often a challenging problem. This study focuses on two small (<2 km2) temperate glaciers in the Hohe Tauern (Eastern Alps) region of central Austria. The period 2003–04 saw the first use of ground-penetrating radar (GPR) to determine the total ice volume and ice-thickness distribution of the two glaciers. A centre frequency of 20 MHz was used in point measuring mode. Despite variable data quality, bedrock reflections up to depths of >100m were identified in the data. The acquired GPR data are irregularly distributed and the spatial density is too low to calculate reasonable bedrock topography with standard interpolation approaches. Thus one main focus of this study was to develop an appropriate interpolation technique. Eventually, kriging technique and a glacial mechanically based interpolation parameter were used. Mean calculated ice thicknesses for the two investigated glaciers are 40–50 m, with a maximum of 150–165 m. No direct validation data are available, so different considerations support the computed bedrock topography.

Comparison of Pediatric Cardiac Surgical Mortality Rates From National Administrative Data to Contemporary Clinical Standards

Despite the superior coding and risk adjustment of clinical data, the ready availability, national scope, and perceived unbiased nature of administrative data make it the choice of governmental agencies and insurance companies for evaluating quality and outcomes. We calculated pediatric cardiac surgery mortality rates from administrative data and compared them with widely quoted standards from clinical databases. Pediatric cardiac surgical operations were retrospectively identified by ICD-9-CM diagnosis and procedure codes from the Nationwide Inpatient Sample (NIS) 1988-2005 and the Kids' Inpatient Database (KID) 2003. Cases were grouped into Risk Adjustment for Congenital Heart Surgery, version 1 (RACHS-1) categories. In-hospital mortality rates and 95% confidence intervals were calculated. A total of 55,164 operations from the NIS and 10,945 operations from the KID were placed into RACHS-1 categories. During the 18-year period, the overall NIS mortality rate for pediatric cardiac surgery decreased from 8.7% (95% confidence interval, 8.0% to 9.3%) to 4.6% (95% confidence interval, 4.3% to 5.0%). Mortality rates by RACHS-1 category decreased significantly as well. The KID and NIS mortality rates from comparable years were similar. Overall mortality rates derived from administrative data were higher than those from contemporary national clinical data, The Society of Thoracic Surgeons Congenital Heart Surgery Database, or published data from pediatric cardiac specialty centers. Although category-specific mortality rates were higher in administrative data than in clinical data, a minority of the relationships reached statistical significance. Despite substantial improvement, mortality rates from administrative data remain higher than those from clinical data. The discrepancy may be attributable to several factors: differences in database design and composition, differences in data collection and reporting structures, and variation in data quality.

Geological Atlas of Africa, with Notes on Stratigraphy, Tectonics, Economic Geology, Geohazards, Geosites and Geoscientific Education of Each Country. 2nd Edition.: THOMAS SCHLUTER. Pp 308, with CD-ROM. Springer-Verlag, Berlin, Germany. 2008. ISBN 9787 -3-540-76324-6.Price USD249.00.

Geological Atlas of Africa, with Notes on Stratigraphy, Tectonics, Economic Geology, Geohazards, Geosites and Geoscientific Education of Each Country is a four-color, revised and enlarged second edition, first published in 2006. Brief reviews of “Aims and Concepts of the Atlas” (6 pages), “Early Geological Maps of Africa” (4 pages), and “Tectonostratigraphic Synopsis” (15 pages) are followed by the heart of the book, 246 pages in which 58 individual African countries are covered. The “Tectonostratigraphic Synopsis,” listed above, is a geologic synthesis that covers all of Africa in 15 pages. As such, it is very broad, reflecting the very variable quality of data that are available on the countries of Africa. However, it is a useful overview for those unfamiliar with African geology. The assorted six maps provide a useful background and would have been …

Sensitivity of a soil-vegetation-atmosphere-transfer scheme to input data resolution and data classification

This paper presents modelling of the effects of input data resolution and classification of a regionally applied soil-vegetation-atmosphere-transfer (SVAT) scheme. Most SVAT schemes were developed at local scales but often are applied at regional scales to simulate regional water balances and to predict effects of environmental changes on catchment hydrology. Applying models at different scales requires investigating sensitivity to the available input data. In this study, investigated input data include soil maps, vegetation classifications, topographic information and weather data of varying temporal and spatial resolutions. Target quantities are simulated water fluxes such as evapotranspiration rates, groundwater recharge and runoff generation rates. Model sensitivity is estimated with respect to water balances and water flows, focusing on different time periods (months, years). The soil vegetation atmosphere transfer scheme SIMULAT is applied to two different catchments representing different environments where data sets of varying data quality and resolution are available. Results show that, on an annual time scale, SIMULAT is most sensitive to aggregation of soil information and mis-classification in vegetation data. On the monthly time scale, SIMULAT is also very sensitive to disaggregation of precipitation data. The sensitivity to spatial distribution of land-use data and spatio-temporal resolution of weather data is low. Based on the investigations, a ranking of the sensitivity of the model to resolution and classification of different input data sets is proposed. Minimum requirements concerning data resolution for regional scale SVAT applications are derived.

2× genomes—Does depth matter?: Table 1.

2× genomes—Does depth matter?: Table 1.

Petroleum systems and structures offshore central West Greenland: implications for hydrocarbon prospectivity

A detailed geophysical mapping project has been carried out by the Geological Survey of Denmark and Greenland (GEUS) in the offshore region south-west and west of Disko and Nuussuaq, central West Greenland as part of the preparations for the Disko West Licensing Round in 2006 (Fig. 1). The main purpose of the study was to evaluate the prospectivity of this almost 100 000 km2 large region, and to increase knowledge of basin evolution and the structural development. Results of the work, including a new structural elements map of the region and highlights of particular interest for hydrocarbon exploration of this area, are summarised below. Evidence of live petroleum systems has been recognised in the onshore areas since the beginning of the 1990s when seeps of five different oil types were demonstrated (Bojesen-Koefoed et al. 1999). Oil seeps suggesting widely distributed marine source rocks of Mesozoic age are particularly promising for the exploration potential (Bojesen-Koefoed et al. 2004, 2007). Furthermore, possible DHIs (Direct Hydro carbon Indicators) such as gas-clouds, pock marks, bright spots and flat events have been interpreted in the offshore region (Skaarup et al. 2000; Gregersen & Bidstrup in press). The evaluation of the region (Fig. 1) is based on all public and proprietary seismic data together with public domainmagnetic and gravity data. The seismic data (a total of c. 28 000 line km) are tied to the two existing offshore exploration wells in the region (Hellefisk-1 and Ikermiut-1). The study also incorporates information on sediments and volcanic rocks from onshore Disko and Nuussuaq (Fig. 2). Ten seismic horizons ranging from ‘mid-Cretaceous’ to ‘Base Quaternary’ (Fig. 2) have been interpreted regionally. Large correlation distances to wells, varying data quality and a thick cover of basalt in the north-eastern part of the region, add uncertainty in the regional interpretation, especially for the deeper horizons such as the ‘mid-Cretaceous’ equivalent to Santonian sandstone interval drilled in Qulleq-1 far south. Based on the seismic interpretation (Fig. 3) structural elements maps, horizon-depth maps and isopach maps have been produced; these maps, together with general stratigraphic knowledge on potential reservoirs, seals and source rocks (Fig. 2), provide important information for discussions of critical play elements including kitchens and structures.The existence of many large structures combined with the evidence of live petroleum systems has spurred the recent major interest for hydrocarbon exploration in the region.

Preparing DNA from Blood for Genotyping

INTRODUCTIONThis protocol describes the extraction of genomic DNA from whole blood samples (fresh or frozen) and buffy coats. It provides methods for (1) large-scale extraction of DNA using either in-house or commercial (PUREGENE) reagents; (2) mid-scale extraction of DNA using the QIAamp DNA Blood Midi Kit (for 0.5-mL samples); and (3) small-scale extraction of DNA using the QIAamp DNA Blood Mini Kits (for 200-μL samples). Also included are methods for extracting DNA from blood samples that are compromised or clotted. Compromised blood samples include samples that spent more than 3 days in transit, samples that have been stored for more than 1 wk at 4°C, samples that have been stored at -20°C or -70°C, and samples that were collected incorrectly (e.g., not mixed properly). The procedures described here are not high throughput. Potential drawbacks of making them high-throughput are lower recoveries of DNA and possible variability in data quality, thus requiring additional quality assurance and control checks. DNA yields for these methods vary with the number of nucleated cells in the blood sample and the quality of the sample.

Accuracy of birth certificate data by risk factors and outcomes: analysis of data from New Jersey

The purpose of this study was to determine the extent to which the accuracy of birth certificate data varies by risk factors and birth outcomes. We reanalyzed data from a validation study of birth certificate data in New Jersey, focusing on subgroups of mothers according to marital status, age, race, ethnicity, English-language proficiency, prenatal care, transfer status, birthweight, and gestational age. Underreporting of birth certificate data elements varies by maternal characteristics (particularly English-language proficiency), transfer status, and birth outcomes. It is important to consider subgroup variations in data quality when birth certificate data are used for research. Additional studies are needed to explore the sources of variation in data quality and to assess the quality for additional subgroups, across subgroups in other states, in low-risk populations, and of new data items that were introduced in the 2003 revision of the US Standard Certificate of Live Birth.

Modeling the effects of varying data quality on trend detection in environmental monitoring

Detection of changes in ecosystem characteristics is a principal tool for identifying and understanding the effects of anthropogenic activities on the condition and functioning of ecosystems. It is widely known that temporal trends can be blurred by the imprecision of the data. Research program managers are aware of the difficulties surrounding representative sampling and therefore enforce strict sampling protocols. Standardized sampling can be so effective that the initially much smaller uncertainty in the instrumental analysis becomes substantial. However, until now the effect of the quality of the instrumental analysis on the time required for trend detection has only rarely been quantified. In this paper, we present a novel technique and theoretical computations for the detection of trends in single and combined indices. The theory is clarified with examples from the International Co-operative Programme on Assessment and Monitoring of Air Pollution on Forests (ICP Forests). Moreover, the theoretical computations were made for normalized or scaled distributions and are therefore equally valid outside the field of environmental monitoring. The results show that, when sampling protocols largely reduce the variability of representative sampling, poor quality of the instrumental analysis blurs the data such that environmental monitoring or long-term ecological research programs can lose the ability to detect trends by causing up to three decades-long delay in detecting changes. We can thus conclude that high quality of the instrumental analysis is a prerequisite for a sensitive monitoring program.

Data quality initiatives: striving for continuous improvements

Although managers consider accurate, timely, and relevant information as critical to the quality of their decisions, evidence of large variations in Data Quality (DQ) abounds. Over a period of 12 months, the research project reported herein investigated and tracked DQ initiatives undertaken by the participating organisation. The results confirmed that, to ensure and maintain DQ, commitment to continuous DQ improvement is necessary. Most importantly, the research found that sustaining DQ gains requires mutual understanding by operations personnel, management, and funding sources as well as the provision of adequate incentives and modifications to institutional constraints.

Using VSP surveys to bridge the scale gap between well and seismic data

Abstract This case study was undertaken for a low-porosity fractured carbonate reservoir with a complex fracture network resulting from several phases of tectonic activity. The integration of the image log and seismic-derived interpretations was problematic due to the complexity of the image log signature and the variable quality of the surface seismic data. Earlier experience indicated that VSPs may provide information on faulting and/or fracturing that may otherwise be difficult to determine with confidence from other data sources. Consequently, specialist VSP processing techniques were used to identify and map reflectors in three-dimensional space. Data acquired in two wells were reprocessed to interpret structural features and determine their geometries. The interpreted VSP reflectors were validated and integrated with the analyses of image logs and the interpretation of surface seismic data providing a constrained structural model that allowed the interpretation of seismic data away from well control and provided a starting point for seismic interpretation in areas where structural geometries were poorly imaged on surface seismic. It is shown that VSP, including vertical incidence, data can contribute to the understanding of reservoirs and enables well-derived information to be extrapolated away from the wells.

Numerical evaluation of thermal response tests

Thermal conductivity is a key parameter in the design of borehole heat exchangers. Thermal response tests are becoming increasingly more popular for measuring in situ thermal conductivity but no theoretical investigations have been done so far that account for three-dimensional effects. We compared the results from a 3-D finite-element numerical model with those of a simple analytical line-source solution and tested their sensitivity to the duration of the tests. The effects of heterogeneous subsurface conditions, groundwater movement, and variable data quality are presented. Comparison with measured data emphasizes the importance of using more sophisticated numerical methodologies in interpreting thermal response test data.

A five‐year audit of anal cancer in Wales

A retrospective audit has been undertaken of Squamous (epidermoid) type of anal cancer diagnosed and treated in the principality of Wales over a five-year period (1995-99) with follow-up until 2005. The referral pattern, distribution, presenting symptoms, predisposing conditions, clinical findings and staging modalities were documented. The surgical and oncological treatment together with their outcome was analysed. Patients were identified from the Welsh Cancer Registry and the pathology databases of the 17 acute hospitals in Wales. Data was collected from the clinical and oncology case notes onto a purpose designed Microsoft access database. There was a wide variation in data quality from the individual units. Twenty-six anal cancers were diagnosed per year in the region. Median age was 69 years. Ten percent had documented perianal Human Papilloma Virus related disease. Radiology was inconsistently used for staging. Eighty percent were referred for an oncology opinion; 50% had chemo-radiotherapy with a curative intent. The over-all Stoma rate was 35% and of these 18% had an abdomino perineal resection. The overall five-year survival was 45%. This is a unique regional audit of anal cancer. Improvements need to be made in documentation particularly of staging, treatment, pathology reporting and outcome. This study concurs that Human Papilloma Virus appears to predispose to Squamous anal cancer. Radiological staging needs to be standardized according to best clinical practice. As recommended by NICE all patients should be referred to a multidisciplinary anal cancer team, which can provide individual treatment plans. Increased specialization could mean specialist regional MDTs for anal cancer.

Evaluation of the National Congenital Anomaly System in England and Wales

Objective: To evaluate the National Congenital Anomaly System (NCAS). Methods: The NCAS in England and Wales based at the Office for National Statistics and the various regional registers that exchange...

Validation of surgical site infection surveillance data in Scotland

Validation of surveillance data is necessary to ensure its scientific credibility, to identify methodological problems within the surveillance programme, to help increase compliance and participation in the surveillance programme, and to identify data quality issues at local level. Surgical site infection surveillance (SSIS) in Scotland has been implemented in collaboration between Health Protection Scotland (HPS) and staff in acute divisions in Scotland. A team at HPS carried out a study to validate the SSIS data reported to them. The aims of the validation study were: (i) to measure the completeness of the denominator data; (ii) to measure the accuracy of all SSIS data items reported to HPS; and (iii) to determine the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the SSIs reported to HPS against the SSIs validated as part of this study. The methodology utilized for validation of SSIS data was based on an evaluation research approach. The evaluation research approach involves a range of investigative activities, aimed at judging the worth of a programme or practice, and measures SSIS in terms of structure, process and outcome. The completeness of the denominator and the means of identifying eligible patients was identified. Descriptive information about how SSIS data were collected and managed at hospital level was collated, and the accuracy and completeness of the reported SSIS data were measured by case note review of selected cases. SSIS data from 27 hospitals in 15 acute divisions and one special health board were validated. The results indicated that a total of 91% of the procedures carried out (denominator) during a specified three-month period were reported to HPS. The case notes validated over 90% of records reported to HPS; however, there was variation in data quality between hospitals. The sensitivity, specificity, PPV and NPV of the SSIs reported to HPS were 96.7, 99.0, 94.6 and 99.4%, respectively. Where problems with data were identified at local level, hospitals have been offered guidance to improve their data. As a result of this study, HPS are confident that the Scottish SSIS data are reliable and robust.

Prevention of mother-to-child transmission and voluntary counseling and testing programme data: what is their utility for HIV surveillance?

Antenatal clinic (ANC)-based surveillance through unlinked anonymous testing (UAT) for HIV without informed consent provides solid long-term trend data in resource-constrained countries with generalized epidemics. The rapid expansion of the prevention of mother-to-child transmission (PMTCT) and voluntary counseling and testing (VCT) programmes prompts the question regarding their utility for HIV surveillance and their potential to replace UAT-based ANC surveillance. Four presentations on the use of PMTCT or VCT data for HIV surveillance were presented at a recent international conference. The main findings are presented in this paper, and the operational and epidemiological aspects of using PMTCT or VCT data for surveillance are considered. VCT data in Uganda confirm the falling trend in HIV prevalence observed in ANC surveillance. Thailand, a country with nationwide PMTCT coverage and a very high acceptance of HIV testing, has replaced UAT data in favor of PMTCT data for surveillance. Studies from Botswana and Kenya showed that PMTCT-based HIV prevalences was similar, but the quality and availability of the PMTCT data varied. The strength of UAT lies in the absence of selection bias and the availability of individual data. Conversely, the quantity of VCT and PMTCT programme testing data often exceed those in UAT, but may be subject to bias due to self-selection or test refusal. When using VCT or PMTCT data for surveillance, investigators must consider these caveats, as well as their varying data quality, accessibility, and availability of individual records.

Improving carrier-phase ambiguity resolution in global GPS network solutions

Integer carrier-phase ambiguity resolution is one of the critical issues for precise GPS applications in geodesy and geodynamics. To resolve as many integer ambiguities as possible, the ‘most-easy-to-fix’ double-difference ambiguities have to be defined. For this purpose, several strategies are implemented in existing GPS software packages, such as choosing the ambiguities according to the baseline length or the variances of the estimated real-valued ambiguities. Although their efficiencies are demonstrated in practice, it is proven in this paper that they do not reflect all effects of varying data quality, because they are based on theoretical considerations of GPS data processing. Therefore, a new approach is presented, which selects the double-difference ambiguities according to their probability of being fixed to the nearest integer. The probability is computed from estimates and variances of wide-lane and narrow-lane ambiguities. Together with an optimized ambiguity fixing procedure, the new approach is implemented in the routine data processing for the International GPS Service (IGS) at GeoForschungsZentrum (GFZ) Potsdam. Within a sub-network of about 90 IGS stations, it is demonstrated that more than 97% of the independent ambiguities are fixed correctly compared to 75% by a commonly used method, and that the additionally fixed ambiguities improve the repeatability of the station coordinates by 10–26% in regions with sparse site distribution.

The quality of the quality indicator of pain derived from the minimum data set.

To examine facility variation in data quality of the level of pain documented in the minimum data set (MDS) as a function of level of hospice enrollment in nursing homes (NHs). Clinical assessments on 3,469 nonhospice residents from 178 NHs were merged with On-line Survey Certification and Reporting data of 2000, Medicare Claims data of 2000 and the MDS of 2000-2002. Using the same assessment protocol, NH staff and study nurses independently assessed 3,469 nonhospice residents. Study nurses' assessments being gold standard, we quantified and compared quality of NH staff's pain rating across NHs with high, medium, or low hospice use. Multilevel models were built to assess the effect of NH hospice use levels on the occurrence of false positive (FP) and false negative (FN) errors in NH-rated "severe pain." Of 178 NHs, 25 had medium and 41 high hospice use. NHs with higher hospice use had lower sensitivities. In multilevel analysis, we found a significant facility-level variation in the probability of FP and FN errors in facility-rated "severe pain." Resident characteristics only explained 4 and 0 percent of the facility variation in FP and FN, respectively; characteristics and locations (state) of NHs further explained 53 and 52 percent of the variance. After controlling for resident and NH characteristics, staff in NHs with medium or high hospice use were less likely to have FP or FN errors in their MDS documentation of pain than were staff in NHs with low or no hospice use. The examination of data quality of pooled MDS data from multiple NHs is insufficient. Multilevel analysis is needed to elucidate sources of heterogeneity in the quality of MDS data across NHs. Facility characteristics, e.g., hospice use or NH location, are systematically associated with overrated/underrated pain and may bias pain quality indicator (QI) comparisons. To ensure the integrity of QI comparison in the NH setting, the government may need to institute regular audits of MDS data quality.