Scholar’s Introducation

Prof.&Ph .DZHUQingZHUQing ,professor,Ph .D ,Ph .Dsupervi sor ,wasborninRenshoucountyofSichuanprovincein 1 966.HegraduatedfromDepartmentofRailwayEngineeringofSouthwesternJiaotongUniversity (SWJTU)in 1 986,withB .E .degreemajoringinphotogrammetryandremotesensing .Inthesameyear,hewasrecommendedasapostgraduatesupervisedbyProf.MADeyan ,andmajoredinComputerAidedCartography (CAC) .In 1 989,hereceivedM .E .degreeandthenbe cameateacherinSWJTU .From 1 990to 1 991 ,heworkedintheThirdI…     

Scholar’s Introduction

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On Helmert’s methods of condensation

Helmerts first and second method of condensation are reviewed and generalized in two respects: First, the point at which the effects of topographical and condensation masses are calculated may be situated on or outside the topographical surface; second, the depth of the condensation layer below the geoid is arbitrary. While the first extension permits the application of the generalized model to the evaluation of airborne and satellite data, the second one gives an additional degree of freedom which can be used to provide a smooth gravity field after reducing the observation data. The respective formulae are derived for the generalized condensation model in both planar and spherical approximation. A comparison of the planar and the spherical model shows some structural differences, which are primarily visible in the out-of-integral terms. Considering the respective formulae for the combined topographic–condensation reduction on the background of the density structure of the Earths lithosphere, the consequences for the residual gravity field are investigated; it is shown that the residual field after applying Helmerts second model of reduction is very rough, making this procedure unfavourable for downward continuation. Further considerations refer to the question of which sets of formulae should be used in geoid and quasigeoid determination. It is concluded that for high-precision applications the generalized spherical model, involving a depth of the condensation layer of between 20 and 30 km, should be superior to Helmerts second model of condensation, although it requires the direct calculation of the indirect effect, which is larger than in the case of Helmerts second method of condensation.     

Isard’s contributions to spatial interaction modeling

This short review, surveys Isards role in promoting what has become known as spatial interaction modeling. Some contextual information on the milieu from which his work emerged is given, together with a selected number of works that are judged to have been influenced (directly and indirectly) by his work. It is suggested that this burgeoning field owes a lot to the foundations laid in the gravity model chapter of Methods. The review is supplemented by a rather extensive bibliography of additional works that are indicative of the breadth of the impact of this field.     

Conversion of time-varying Stokes coefficients into mass anomalies at the Earth’s surface considering the Earth’s oblateness

Time-varying Stokes coefficients estimated from GRACE satellite data are routinely converted into mass anomalies at the Earth’s surface with the expression proposed for that purpose by Wahr et al. (J Geophys Res 103(B12):30,205–30,229, 1998). However, the results obtained with it represent mass transport at the spherical surface of 6378 km radius. We show that the accuracy of such conversion may be insufficient, especially if the target area is located in a polar region and the signal-to-noise ratio is high. For instance, the peak values of mean linear trends in 2003–2015 estimated over Greenland and Amundsen Sea embayment of West Antarctica may be underestimated in this way by about 15%. As a solution, we propose an updated expression for the conversion of Stokes coefficients into mass anomalies. This expression is based on the assumptions that: (i) mass transport takes place at the reference ellipsoid and (ii) at each point of interest, the ellipsoidal surface is approximated by the sphere with a radius equal to the current radial distance from the Earth’s center (“locally spherical approximation”). The updated expression is nearly as simple as the traditionally used one but reduces the inaccuracies of the conversion procedure by an order of magnitude. In addition, we remind the reader that the conversion expressions are defined in spherical (geocentric) coordinates. We demonstrate that the difference between mass anomalies computed in spherical and ellipsoidal (geodetic) coordinates may not be negligible, so that a conversion of geodetic colatitudes into geocentric ones should not be omitted.     

A Synopsis of Nigeria’s Indigenous Cartographic Heritage

Abstract

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Over the ages, Nigerians have had various indigenous ways of spatial representation, otherwise known as ‘alternative cartographies’. Paradoxically, however, the indigenous cartographic heritage of the Nigerian people has altogether remained unsung despite its immense contributions to societal development. This paper, therefore, is a modest attempt aimed at bringing the forgotten issue of Nigeria’s cartographic legacy to the limelight. The paper takes a bird’s-eye look at Nigeria’s homegrown cartographic heritage. The various local means of representing and communicating geospatial information are discussed. The paper equally highlights the invaluable benefits of indigenous cartographic heritage as well as how to preserve such heritage.     

Floor positioning method indoors with smartphone’s barometer

ABSTRACT

This paper presents an indoor floor positioning method with the smartphone’s barometer for the purpose of solving the problem of low availability and high environmental dependence of the traditional floor positioning technology. First, an initial floor position algorithm with the “entering” detection algorithm has been obtained. Second, the user’s going upstairs or downstairs activities are identified by the characteristics of the air pressure fluctuation. Third, the moving distance in the vertical direction and the floor change during going upstairs or downstairs are estimated to obtain the accurate floor position. In order to solve the problem of the floor misjudgment from different mobile phone’s barometers, this paper calculates the pressure data from the different cell phones, and effectively reduce the errors of the air pressure estimating the elevation which is caused by the heterogeneity of the mobile phones. The experiment results show that the average correct rate of the floor identification is more than 85% for three types of the cell phones while reducing environmental dependence and improving availability. Further, this paper compares and analyzes the three common floor location methods – the WLAN Floor Location (WFL) method based on the fingerprint, the Neural Network Floor Location (NFL) methods, and the Magnetic Floor Location (MFL) method with our method. The experiment results achieve 94.2% correct rate of the floor identification with Huawei mate10 Pro mobile phone.     

On computing ellipsoidal harmonics using Jekeli’s renormalization

Gravity data observed on or reduced to the ellipsoid are preferably represented using ellipsoidal harmonics instead of spherical harmonics. Ellipsoidal harmonics, however, are difficult to use in practice because the computation of the associated Legendre functions of the second kind that occur in the ellipsoidal harmonic expansions is not straightforward. Jekeli’s renormalization simplifies the computation of the associated Legendre functions. We extended the direct computation of these functions—as well as that of their ratio—up to the second derivatives and minimized the number of required recurrences by a suitable hypergeometric transformation. Compared with the original Jekeli’s renormalization the associated Legendre differential equation is fulfilled up to much higher degrees and orders for our optimized recurrences. The derived functions were tested by comparing functionals of the gravitational potential computed with both ellipsoidal and spherical harmonic syntheses. As an input, the high resolution global gravity field model EGM2008 was used. The relative agreement we found between the results of ellipsoidal and spherical syntheses is 10^?14, 10^?12 and 10^?8 for the potential and its first and second derivatives, respectively. Using the original renormalization, this agreement is 10^?12, 10^?8 and 10^?5, respectively. In addition, our optimized recurrences require less computation time as the number of required terms for the hypergeometric functions is less.     

Geographic Reality Versus Imagination in Taiwan’s Historical Maps

Abstract

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During the past 400?years, Taiwan has experienced the dominance of various political regimes, which allowed the development of a diversity of cartographic styles for academic comparison. A detailed analysis of historical maps across centuries demonstrates that this contested island has been illustrated with a blending of reality, misconception and imagination. This paper narrates how maps reveal political rulers’ conscious and unconscious perceptions of this island. We call attention to the abundant cartographic materials in existence and suggest that they can be fascinating materials for the study of the contested colonial histories of this island in various disciplines.     

Bertin’s forgotten typographic variables and new typographic visualization

ABSTRACT

Typographic variables were only briefly discussed by Bertin with no example applications. We review historic examples to extend Bertin’s framework with literal encoding, 10 typographic attributes, variations on scope including characters, words, phrases and paragraphs, and more layout types. We then apply the framework to Bertin’s population dataset to create 11 new typographic visualizations. The approach raises questions for new research such as readability, semantic association, interaction, and comprehension.     

Jacques Bertin’s legacy and continuing impact for cartography

Quality is critical in cartography because key decisions are often made based on the information the map communicates. The mass production of digital cartographic information to support geographic information science has now added a new dimension to the problem of cartographic quality, as problems once limited to small volumes can now proliferate in mass production programs. These problems can also affect the economics of map production by diverting a sizeable portion of production cost to pay for rework on maps with poor quality. Such problems are common to general industry—in response, the quality engineering profession has developed a number of successful methods to overcome these problems. Two important methods are the reduction of error through statistical analysIs and addressing the quality environment in which people work. Once initial and obvious quality problems have been solved, outside influences periodically appear that cause adverse variations in quality and consequently increase production costs. Such errors can be difficult to detect before the customer is affected. However, a number of statistical techniques can be employed to detect variation so that the problem is eliminated before significant damage is caused. Additionally, the environment in which the workforce operates must be conducive to quality. Managers have a powerful responslblhty to create this environment. Two sets of guidelines, known as Deming's Fourteen Points and ISO-9000, provide models for this environment.     

Accuracy assessment of the National Geodetic Survey’s OPUS-RS utility

OPUS-RS is a rapid static form of the National Geodetic Survey’s On-line Positioning User Service (OPUS). Like OPUS, OPUS-RS accepts a user’s GPS tracking data and uses corresponding data from the U.S. Continuously Operating Reference Station (CORS) network to compute the 3-D positional coordinates of the user’s data-collection point called the rover. OPUS-RS uses a new processing engine, called RSGPS, which can generate coordinates with an accuracy of a few centimeters for data sets spanning as little as 15 min of time. OPUS-RS achieves such results by interpolating (or extrapolating) the atmospheric delays, measured at several CORS located within 250 km of the rover, to predict the atmospheric delays experienced at the rover. Consequently, standard errors of computed coordinates depend highly on the local geometry of the CORS network and on the distances between the rover and the local CORS. We introduce a unitless parameter called the interpolative dilution of precision (IDOP) to quantify the local geometry of the CORS network relative to the rover, and we quantify the standard errors of the coordinates, obtained via OPUS-RS, by using functions of the form