Level Tools Research Articles

The worldwide physical height datum project

The definition of a common global vertical coordinate system is nowadays one of the key points in Geodesy. With the advent of GNSS, a coherent global height has been made available to users. The ellipsoidal height can be obtained with respect to a given geocentric ellipsoid in a fast and precise way using GNSS techniques. On the other hand, the traditional orthometric height is not coherent at global scale. Spirit levelling allows the estimation of height increments so that orthometric heights of surveyed points can be obtained starting from a benchmark of known orthometric heights. As it is well known, this vertical coordinate refers to the geoid, which is assumed to be coincident to the mean sea level. By means of a tide gauge, the mean sea level is estimated and thus a point of known orthometric height is defined. This assumption, which was acceptable in the past, became obsolete given the level of precision which is now required. Based on the altimetry observation, one can precisely quantify the existing discrepancy between geoid and mean sea level that can amount to 1 ÷ 2 m at global scale. Therefore, different tide gauges provide biased estimates of the geoid, given the discrepancy between this equipotential surface and the mean sea level. Also, in the last years, another vertical coordinate was used, the normal height that was introduced in the context of the Molodensky theory. In this paper, a review of the existing different height systems is given and the relationships among them are revised. Furthermore, an approach for unifying normal height referring to different tide gauges is presented and applied to the Italian test case. Finally, a method for defining a physical height system that is globally coherent is discussed in the context of the definition of the International Height Reference System/Frame, a project supported by the Global Geodetic Observing System of the International Association of Geodesy (IAG). This project was established in 2015 during the XXVI IAG General Assembly in Prague as described in IAG Resolution no. 1 that was presented and adopted there.

Comparative Analysis of Change between Ellipsoidal Height Differences and Equivalent Orthometric Height Difference

Height is an important component in the determination of the position of a point. The study aimed at performing a comparative analysis of change between ellipsoidal height differences and the equivalent orthometric height difference of points. A hi-target Differential Global Positioning System (DGPS) was used to acquire GPS data with an occupation period of thirty (30) minutes on each point, which were processed using Hi-target Geomatics Office (HGO) software to obtain the ellipsoidal heights. An automatic level instrument was used to acquire leveling data, which were processed using the height of collimation method to obtain the orthometric heights. A total of fifty (50) points were occupied as common points for both the GPS and levelling observations at 20-meter intervals. The accuracy of the height difference was determined using standard deviation with the ellipsoidal height difference as 53.59cm and the orthometric height as 53.07cm respectively. A Root Mean Square Error value of 0.0621m was obtained as the accuracy of the change between the two height differences. Statistical analysis using the independent-sample Z test was used to analyze the data at a 5% significant level. The result shows no significant difference in the performance of the two height systems. It is worthy to note that GPS and spirit levelling height differences can be used interchangeably for any heighting in short distances for surveying and engineering applications.

Active Steady‐State Creep on A Nontectonic Normal Fault in Southeast Utah: Implications for Strain Release in a Rapidly Deforming Salt System

AbstractCharacterizing short‐term temporal variations of fault creep provide insight into the evolution, mechanics, and strength of fault systems. Using spirit leveling and an extensometer, we measured active slip of a surface fault southwest of the Needles District, Canyonlands National Park, Utah, where exteis driven by differential unloading of a subsurface salt layer due to incision of the Colorado River. Results show continuous creep at maximum rates of 0.7 ± 0.2 mm/yr without large temporal variations typical of episodic creep events. Occasional, minor transient events in fault slip velocity coincided with water infiltration; however, we found no significant relation between precipitation and transient events. Detailed mapping of widespread, fault‐parallel sinkholes provide evidence for dilation of faults at shallow depth, a process that lowers fault strength. We propose continuous slip is related to low fault strength and differential unloading, as opposed to other salt systems where dissolution has been linked to episodic slip.

Absolute vertical motion of the Amsterdam Ordnance Datum (NAP)

Abstract. The backbone of the Amsterdam Ordnance Datum (NAP) is a network of about 400 primary subsurface markers. Relative movements between the primary subsurface markers are measured with spirit levelling once in 10–20 years. However, little is known about absolute vertical movements of the primary network. This information is indispensable for the interpretation of water level measurements at the tide gauges along the Dutch coast. It may be provided by gravity measurements. Here we present a time-series analysis of more than twenty years of gravity measurements at the stations Westerbork, Epen, Zundert, and Radio Kootwijk. It reveals that only station Epen shows a statistically significant movement of -0.252±0.066 µGal yr−1, which corresponds to an uplift of 1.3±0.5 mm yr−1. For the other stations, the trends are statistically not different from zero at a significance level of 0.05. Corrections for water table variations are found to be indispensable; peak-to-peak amplitudes range from 4 µGal (Westerbork) to 28 µGal (Radio Kootwijk). Depsite some fundamental objections, corrections for instrumental offsets reduce the data scatter. First experiments with 7 years of soil moisture data acquired at station Radio Kootwijk reveal that the gravity signal of soil moisture variations has a standard deviation of 2.2 µGal, which is comparable to the noise standard deviation of measured gravity.

The Contribution of Business Management Trainings on Women Smallholder Farmers’ Entrepreneurial Spirit in Siteki Area of Eswatini

Women make essential contributions to the agricultural and rural economies in most developing countries including Eswatini yet they are the most visible face of poverty. As a strategy of empowering women to up-lift them from abject poverty, “Luhlelo Lolunotsisa Temabhizinisi” (LULOTE) has developed business management training programs for rural women smallholder farmers to enhance their entrepreneurship spirit and skills. The LULOTE in English can be interpreted as a program that helps businesses to advance/prosper. It is a Non-Governmental Organization was established in 1986 in Eswatini to promote entrepreneurial culture and inspire entrepreneurs. This paper ought to find out the contributions of business management trainings on the level of entrepreneurial spirit and skills of women smallholder farmers as its main objective. Data was collected through the use of questionnaires and personal interviews with a sample size of 120 farmers. Descriptive statistics and the Ordinary Least Square (OLS) multiple regression models were used as methods of analysis. The results of this study indicate that most farmers interviewed were aged above 49 years, married (40%), and primary school dropout (mean of 6 years in school), spent an average of 10 years in farming and at least 50% on average indicated that farming was their main occupation. Results further revealed that the trained women by LULOTE had a higher entrepreneurial spirit than the non-trained women scoring an average index of 3.45 and 2.77, respectively. The LULOTE trained women also were rated higher with a 3.50 score compared to the non-trained rated at 3.01 scores. The determinants of level of entrepreneurial spirit among sampled women included age of respondent, level of education, farming as major occupation, and incomes from remittances. Determinants of level of entrepreneurial skills among sampled women included, farming income, off-farm income and previous job of the respondent. Based on the independent T-test results, there was a significant difference in the statements mean scores related to the level of farmers’ entrepreneurial spirit & Skills between LULOTE members and non-LULOTE members at 1% and 5% level. Therefore, the research concludes that LULOTE trainings greatly contributed to improving the entrepreneurial spirit and skills of the women. Since there is an observable positive result of training women, all stakeholders including government, private sector, Non-Governmental Organizations (NGOs), among others should increase on the training programs for all farming age groups including the youth.

Modelling Orthometric Heights from a Combination of Ellipsoidal Heights and Gravimetric Geoid Model in Rivers State, Nigeria

Many applications in geodesy, hydrography and engineering require geoid-related heights. Spirit leveling which is the traditional means of obtaining geoid- or mean sea level-related heights is slow, time-consuming and costly. Global Navigation Satellite Systems (GNSS) offer faster and relatively cheaper way of obtaining geoid-related heights when geoidal undulation is applied to ellipsoidal heights. However, difficulties involved in determining acceptable geoid height have seriously hampered the application of GNSS for leveling in Rivers State, thus necessitating the need to develop an acceptable geoid model which will serve as a means of conversion of GNSS-delivered ellipsoidal heights to their orthometric heights equivalent. In pursuance of this objective, a detailed gravimetric geoid has been evaluated for Rivers State, Nigeria. The computation of the geoid was carried out by the traditional remove-restore procedure. The Earth Geopotential Model 2008 (EGM08) was applied as the reference field for both the remove and restore parts of the procedures; spherical Fast Fourier Transform (FFT) was employed for the evaluation of the Molodenskii’s integral formula for the height anomaly, (ζ) to yield the quasi-geoid; while the Residual Terrain Modelling (RTM) was done by prism integration. The classical gravimetric geoid over Rivers State was obtained from the rigorously evaluated quasi-geoid by adding the quasi-geoid to geoid (N - ζ) correction it. The minimum and maximum geoid height values are 18.599 m and 20.114 m respectively with standard deviation of 0.345 m across the study area. Comparison of the gravimetric geoidal heights with the GPS/Leveling-derived geoidal heights of 13 stations across Rivers State, Nigeria showed that the absolute agreement with respect to the GPS/leveling datum is generally better than 7 cm root mean squares (r.m.s) error. Results also showed that combining both GPS heights and the computed Rivers State geoid model can give orthometric heights accurate to 3 cm post-fit using a 4-parameter empirical model. The geoid model can thus serve as a good alternative to traditional leveling when used with GPS leveling, particularly for third order leveling in the study area.

Social Ills in Rich Countries: New Evidence on Levels, Causes, and Mediators

The income inequality hypothesis claims that in rich societies inequality causes a range of health and social problems (henceforth: social ills), e.g. because economic inequality induces feelings of status anxiety and corrodes social cohesion. This paper provides an encompassing test of the income inequality hypothesis by exploring levels and breeding conditions of social ills in 40 affluent countries worldwide, as well as pathways for a subsample of wealthy European countries. Our aggregate-level research is based on a revised and updated Index of Social Ills inspired by Wilkinson and Pickett’s book The Spirit Level, which we compile for both more countries (40) and more years (2000–2015) and combine with survey information about experienced quality-of-life as potential mediators. We get three major results: First, cross-sectionally income inequality is indeed strongly and consistently related to social ills, but so is economic prosperity. Second, while longitudinally changes in inequality do not result in changing levels of social ills, rising prosperity effectively reduces the amount of social ills, at least in Europe. Finally, whereas the cross-sectional analysis indicates that aspects of social cohesion most consistently mediate between economic conditions and social ills, the longitudinal mediation analyses could not ultimately clarify through which pathway rising prosperity reduces social ills. Overall we conclude that the income inequality hypothesis is, at best, too narrow to fully understand health and social problems in rich countries.

Determination of Vertical Deflection Based on Terestrial Gravity Disturbance Data (A Case Study in Semarang City)

Vertical deflection can be determined by geometrical and physical measurement. In geometrical way, vertical deflection is obtained by comparing astronomical coordinate and geodetical coordinate. In physical way, vertical deflection can be computed from gravity measurement. In the past, vertical deflection was computed from gravity anomaly data. Gravity anomaly data measurement is difficult because it need reduction of gravity from surface of the earth to the geoid using orthometric height from spirit level measurement. In modern era, gravity anomaly data may be replaced by gravity disturbance data whose only required gravity and GNSS (Global Navigation Satellite System) measurement. This research aims to determine vertical deflection in Semarang City from terrestrial gravity disturbance data. The gravity data were measured in March of 2016. Formula of Vening Meinesz that usually used for vertical deflection was replaced by new formula that generated from derivation of function of Hotine. Applying gravity disturbance gave vertical deflection of east-west component that were vary from -1.2” to 12.2” while north-south component were vary from -4.2” to 4.2”. Comparing vertical deflection as computed from terrestrial data to as computed from EGM2008 coefficients showed conformity in shape and values. It was concluded that derivation of function of Hotine could be applied for vertical deflection determination from gravity disturbance.

Сущность любви в Православии

The article analyzes the spiritual and moral field of Orthodox culture and religion, comprehends the essence of love in Orthodoxy, the deep Orthodox roots of marriage and family relations, as well as the problems of modern youth, the influence of Orthodox values on its spiritual formation. It is proved that today more than ever become relevant: patience, mutual understanding, respect, sacrifice, correct hierarchy, getting rid of egocentrism, the unity of spouses, becoming ‘one flesh’ at the level of spirit, soul and body, the idea that following these principles makes it possible to build a really strong family relationships, regardless of the transformational processes that devalue the modern family.

Geoid heights in Costa Rica, Case of Study: Baseline Along the Central Pacific Zone

A precise orthometric height (H) and orthometric height difference (ΔH) determination is required in many fields like construction, geodesy and geophysics. H is often obtained from an ellipsoidal height (h) and geoid height (N) of a geoid model (GM) because this computation does not have the spirit leveling restrictions on long distances. However, the H accuracy depends on the GM local area adaptation, and current global geoid models (GGMs) have not been yet evaluated for Costa Rica. Therefore, this paper aims to determine which GGM maintains a better fit with a GPS/levelling baseline that contains the gravity full spectrum. A 74 km baseline was measured using GPS, spirit leveling and gravity measurements to validate the N computed from EGM2008, EIGEN-6C4, GECO, EGM96, GGM05C and GOCO05C. First, an absolute N assessment was made, where geoid height from the GGMs (NGGM) were directly compared to the geometric geoid heights (Ngeo) obtained from GPS and spirit levelling. A bias fit (Nbias) of about 2 m was computed from this comparison for most GGMs with respect to the local vertical reference surface (W0). By subtracting the Nbias, a relative geoid height (ΔN) assessment was designed to compare the differences between GGM relative geoid height (ΔNGGM) and geometric relative geoid height (ΔNgeo) on segments along the baseline. The ΔN comparison shows that EGM2008, EIGEN-6C4 and GECO better represent the Costa Rican Central Pacific Coastal Zone and over long distances, ΔH can be computed with a decimeter to centimeter precision.

The Double Mediating Effect of Start-Up Motive and Start-Up Spirit between Start-Up Opportunity Awareness and Expected Outcome af a Start-Up

The purpose of this study was to investigate the double mediating effect of start-up motive and start-up spirit between start-up opportunity awareness and expected outcome of a start-up. The subjects of this study were 251 employees living in Seoul, Daejeon, Chungnam, and Chungbuk in Korea. The collected data were analyzed using SPSS PC+ and PROCESS macro. Correlation analysis, reliability analysis, descriptive statistics, and mediation effect analysis were applied for data analysis. First, start-up opportunity awareness was positively correlated with start-up motive, start-up spirit, and the expected outcome of a start-up. Second, the start-up motive mediated the relationship between start-up opportunity awareness and the expected outcome of a start-up. Third, the start-up spirit mediated the relationship between start-up opportunity awareness and the expected outcome of a start-up. Fourth, start-up motive and start-up spirit both mediated the relationship between start-up opportunity awareness and the expected outcome of a start-up. Finally, based on the results of this study, the ways to overcome the low level of start-up spirit and the early closing rate of start-up were discussed

Books: The Inner Level: How More Equal Societies Reduce Stress, Restore Sanity and Improve Everyone's Well-Being: Inequality as it Affects Individuals.

Richard Wilkinson and Kate Pickett. Penguin , 2019 , PB, 352 pp, £9.99 , 978-0141975399 This book should be on every forward-thinking GP’s bookshelf; but unlike many of the other books it should be read and acted upon! Professors Wilkinson and Pickett are epidemiologists and founders of the Equality Trust, which ‘Seeks to promote public understanding of the effects of inequality’ .1 Their original book, called The Spirit Level ,2 has been widely celebrated for highlighting the obvious connection between income inequalities leading to, among other outcomes, health inequalities. The Spirit Level prompted an ‘Equality Pledge’ to be signed by 75 Members of Parliament before the 2010 UK general election, which promised to ‘actively support the case for policies designed to narrow the gap between rich and poor’ . Sadly, as we all know, this hasn’t happened. Wilkinson and Pickett’s central message very much supports Marmot’s theory of the social gradient in health: the higher …

Comparison reproducibility between the facebow and a new technique based on a spirit level device

ABSTRACT Objective: This study aimed to introduce a spirit level device for mounting maxillary casts to compare the reproducibility between the facebow and this new technique. Methods: The maxillary casts of 10 participants were mounted in three different situations: 1) with the facebow; 2) with the spirit level device, the participant in seated position; and 3) with the spirit level device with participant in standing position. Each procedure was performed by three different evaluators. The values obtained were calculated using the Technical Error of Measurement (TEM) and the inter-evaluator Coefficient of Variation (CV). Results: The mean values obtained were 4.3 mm, 2.2 mm, and 2.6 mm for absolute TEM; 8.7%, 5.4%, and 6.4% for relative TEM; and 7.3%, 4.5%, and 5.6% for CV. Conclusion: These results show that the facebow is less reproducible compared to the new device, demonstrating that the new technique can be satisfactorily used in clinical practice.

The gravity database for Belgium

AbstractData and metadata products based on intensive terrestrial gravity measurements covering the Belgian territory have been established compliant to the new ISO19115‐1 profile for gravity‐related data. A short historical introduction on gravity measurements on the Belgian territory is presented, starting with the first gravity measurement in 1892. This paper focuses on gravity data acquired after 1971, which marks the adoption of IGSN71 as a reference for the world network by the International Association of Geodesy (IAG). Next to a complete dataset containing all Belgian gravity data, the available gravity data were reduced to the corresponding measurement campaign, enabling determination of specific metadata (e.g. used gravimeter, tide system parameters, time of acquisition, etc.). New gravity and spirit levelling measurements were executed by the Royal Observatory Belgium and the National Geographic Institute (Federal Mapping Agency) to validate the g‐value at the historical reference base station ‘Carte du Ciel’ in Brussels. Taking into account the instrumental errors and the varying ground water content, the retrieved data are validated and approved for use in further research.

Use of a Digital Protractor and a Spirit Level to Determine the Intraoperative Anteversion of Femoral Component during Cemented Hip Hemiarthroplasty: a Prospective Clinical Trial.

Femoral stem anteversion during hip arthroplasty is generally estimated by eye intraoperatively and has proven to be different from targeted values. This study aims to determine the accuracy of a novel technique using a digital protractor and a spirit level to improve surgeons' estimation of stem anteversion. A prospective non-randomized study was conducted among 93 patients with femoral neck fracture who underwent cemented hemiarthroplasty via posterolateral approach. In the control group (N=62), five experienced surgeons assessed stem anteversion related to the posterior femoral condylar plane using visual estimation with a target angle of 15°-25°. In the study group (N=31), another two surgeons assessed stem anteversion with the same target angle by placing a digital protractor on the femoral stem inserter handle while the assistant held the leg in the truly vertical position, verified by a spirit level that was attached to the shin with cable ties. Stem anteversion was measured blind, postoperatively, on 2D-CT and compared with the intraoperative results. The mean postoperative anteversion was 22.4° (-4.2° to 51.3°, SD 11.1°) in the control group and 23.0° (16.0° to 29.9°, SD 3.6°) in the study group (P=0.810). The study group had more stems positioned in 15°-25° anteversion (71.0% vs 32.3%, P=0.001) and the mean absolute value of surgeon error was -0.2° (-5.4° to 7.0°, SD 3.0°). Twenty-eight stems of the study group (90.3%) had an error within 5°. Surgeon overestimation >5° was found in 1 hip (3.2%) and underestimation >5° was found in 2 hips (6.4%). Using a digital protractor and a spirit level was reliable with high accuracy and precision to improve the intraoperative estimation of cemented stem anteversion.

Performance analysis of multi-GNSS static and RTK techniques in estimating height differences

ABSTRACTEstablishing reliable elevation differences is imperative for most geoscience and engineering applications. This work has traditionally been accomplished through spirit leveling techniques; however, surveyors have been utilizing satellite positioning systems in measuring height differences for more than a decade. Yet the quality of these heights needs to be evaluated in order to adopt them in different applications. In this article, we present the outcome of an accuracy assessment of height differences obtained with static and RTK surveys. Twenty control points with an average baseline length of 1 km were occupied with dual-frequency GNSS receivers for different time periods. Collected signals were processed using open-source software and verified with an online processing tool. Heights were estimated by processing the GPS and the GLONASS data individually, and combined (i.e. GNSS). Height differences were determined and compared with those measured by spirit levels and corrected through geoid models. Best results were achieved by combining GPS and GLONASS solutions for both static and RTK surveys. Solutions with either GPS or GLONASS satellites were comparable, but in most cases, the GPS solutions performed better. For the static surveys, longer occupation provided much accurate height differences. Inconsistencies among 10 different RTK surveys were minimum for the GPS + GLONASS solutions and worst for the GLONASS solutions. The ANOVA, LSD, F, and χ² statistical tests confirmed our findings at the 95% confidence level.

Structural health monitoring of an operational bridge: A case study

During testing of the structural reliability of a prestressed reinforced concrete bridge built in the late 1960s, the author compared the structural responses, performances and costs of jointly conducted static and dynamic load tests. In the static load test, the precision spirit leveling technique was used to measure the deflections of the deck induced by four trucks weighing about 36 tonnes each. In the dynamic load test, accelerometers placed on the main beam were used to measure the vibration frequencies following an impulse produced by a 2-tonne truck. The dynamic load test resulted in a refined finite element model of the bridge. The comparison showed that the dynamic load test can supplement the static load test for the structural testing of new bridges or be an alternative to it for the monitoring of operational bridges.

Aprilsnarren i avisen

Caroline Nyvang: April Fools’ Day in Danish Newspapers
 For more than 400 years, April Fool’s Day has been a legitimate reason to play tricks on those closest to us. In the west, we have a long tradition on this day of sending our family and friends out on wild-goose chases after a smoke-reverser, a left-handed screwdriver or the air-bubble inside a spirit level. Those who took the bait could then be proclaimed April Fool. This article examines how Danish newspapers have managed this tradition from 1849 until today’ The overview takes its empirical starting point in the Mediestream web service’ which gives access to digitalised editions of Danish newspapers published since the 1600s. Through a systematic review of April Fool editions of seven local and nationwide newspapers, I chart three distinct trends in the newspapers’ April Fool jokes. The article shows that what one could joke about and how one could do it has altered in step with the changing conditions for the newspaper medium. In addition, in the article I argue that today, an April Fool joke can best be understood as a variation of news satire’ In the same way as this sub-genre, an April Fool joke gives the media the opportunity to exercise both self-criticism and overall social criticism.

"The Soul Exceeds Its Circumstances": The Later Poetry of Seamus Heaney ed. by Eugene O'Brien

Reviewed by: "The Soul Exceeds Its Circumstances": The Later Poetry of Seamus Heaney ed. by Eugene O'Brien Hunter Dukes (bio) "THE SOUL EXCEEDS ITS CIRCUMSTANCES": THE LATER POETRY OF SEAMUS HEANEY, edited by Eugene O'Brien. Notre Dame: University of Notre Dame Press, 2016. xiv + 403 pp. $50.00 cloth, ebook. "Late as it was,/The early bird still sang," writes Seamus Heaney in "The Tollund Man in Springtime," a sentiment that reverberates through a new edited collection on the poet's later works: Seeing Things, The Spirit Level, Electric Light, District and Circle, and Human Chain.1 These essays examine elements of a poetic landscape that only emerge at dusk but also qualities present since the beginning, clarified through age. The volume is justified by Heaney's own interest in "lateness." As Neil Corcoran observes (108-09), the poet-critic read the final works of Robert Lowell, Patrick Kavanagh, W. H. Auden, and Dylan Thomas through a similar sense of periodization. Many of the essays lapse into a personal mode, saturated with elegy for the poet's passing. Evaluation of Heaney's verse is often preceded by a general praise of character. Eugene O'Brien's introduction sets the tone for this blurring of life and literary output. Thus [End Page 459] we are informed that the poet "was one of the most revered literary figures in the world," whose work is studied at the "very highest level within the academy," forming one of "the greatest collections of lyric poetry in the English language" (1, 3). The nouns Nobel, Harvard, and Oxford recirculate: superlatives abound. There is much to laud. While some essays inhabit a soft border between literary journalism and academic research, Magdalena Kay's dexterous "Death and Everyman: Imagining a 'Not Unwelcoming Emptiness'" (49-70) could stand confidently in either forum. Helen Vendler's "Squarings" (71-85) is memorable for other reasons, moving seamlessly between Renaissance ars memoriae and Heaney's adoption of the douzain form, a twelve-line poetic stanza. One seam does appear: she writes about the "shock" of Seeing Things (84), an argument that turns on Heaney's homage to "Cold Mountain," the English translation for the name of Han-Shan (alternatively spelled Hanshan), a reclusive seventh- or eighth-century Chinese poet who meant a great deal to Gary Snyder and Jack Kerouac; Heaney met the former writer at a party in Berkeley, a character he could imagine "hunkering under a stone wall on the Aran Islands."2 This thread normalizes Heaney's allusion, which becomes a way of squaring "the California distance"—which Vendler herself luminously connects to these poems in Seamus Heaney—with the poet's "Irish memory bank."3 Moynagh Sullivan's essay on Bracha Ettinger and the "Matrixial Gaze" (279-99) refreshes a book heavy on close reading and only occasionally sacrifices clarity for jargon. Chapters by Meg Tyler and Bernard O'Donoghue focus on genetic revision and publication history: an approach thematically warranted in this case, as both scholars reveal how the "later" Heaney honed his earlier efforts. It is inevitable, in an edited collection that exceeds four hundred pages, for there to be repetition and redoubling. Reading the volume cover-to-cover reveals a frustrating dimension of this scholarly form—not the editor's fault, per se, but a missed opportunity nevertheless. I wanted O'Brien's discussion of poetic gifts (342) to connect back to Henry Hart's "Seamus Heaney's Gifts" (219-238), a remarkable essay on "offerings" in Heaney's life and art (wide-ranging, but spotty: Marcel Mauss and Lewis Hyde get air-time, but other thinkers about "gifts" are muted). Elmer Kennedy-Andrews has a wonderful paragraph about bookcases in "The Reluctant Transatlanticist," an essay on Heaney and America, that recalls Michael R. Molino on books and bookshops in Heaney's "Route 110" and Joyce's "Wandering Rocks" and "Araby" (189, 102-04).4 Some details chafe an attentive reader. We learn that Heaney's tercets are inspired by Dante so often that it feels like penance; the Sibyl of Cumae is named with startling frequency, but her presence remains scattered like leaves on the wind; Heaney's parents die over and...

Signal and error assessment of GOCE-based high resolution gravity field models

Abstract The signal content and error level of recent GOCE-based high resolution gravity field models is assessed by means of signal degree variances and comparisons to independent GNSS-levelling geoid heights. The signal of the spherical harmonic series of these models is compared to the pre-GOCE EGM2008 model in order to identify the impact of GOCE data, of improved surface and altimetric gravity data and of modelling approaches. Results of the signal analysis show that in a global average roughly 80% of the differences are due to the inclusion of GOCE satellite information, while the remaining 20% are contributed by improved surface data. Comparisons of the global models to GNSS-levelling derived geoid heights demonstrate that a 1 cm geoid from the global model is feasible, if there is a high quality terrestrial gravity data set available. For areas with less good coverage an accuracy of several centimetres to a decimetre is feasible taking into account that GOCE provides now the geoid with a centimetre accuracy at spatial scales of 80 to 100 km. Comparisons with GNSS-levelling geoid heights also are a good tool to investigate possible systematic errors in the global models, in the spirit levelling and in the GNSS height observations. By means of geoid height differences and geoid slope differences one can draw conclusions for each regional data set separately. These conclusions need to be considered for a refined analysis e.g. to eliminate suspicious GNSS-levelling data, to improve the global modelling by using full variance-covariance matrices and by consistently weighting the various data sources used for high resolution gravity field models. The paper describes the applied procedures, shows results for these geoid height and geoid slope differences for some regional data sets and draws conclusions about possible error sources and future work to be done in this context.