Proceedings of the Institute of Geodesy and Cartography No 112, Vol. LIV
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Grażyna Kloch, Jan Kryński
Implementation of long, medium and short wave components of the signals of functionals of the disturbing potential in the process of modelling geoid
Remove-compute-restore method is commonly used for regional modelling of gravimetric geoid. In this method, which allows to develop precise geoid models using gravity data practically only from the modelled area, functionals of the disturbing potential are expressed in terms of components, which represent different spectral groups. Global geopotential model, gravity anomalies and topographic data are used to determine these components. An important role in modelling geoid, especially with the use of remove-compute-restore technique, plays the type of gravity reductions, and hence the type of gravity anomalies.
In the paper a detailed algorithm of classical technique of modelling geoid is shown, and then free-air, Faye and Helmert gravity anomalies, which are most often used for modelling geoid, are discussed. The description of remove-compute-restore method of geoid modelling is presented in three subsections, where separate spectral components of functionals of the disturbing potential: long, medium and short wave components are discussed. The authors paid attention to the dependence of the method of calculation of medium and short wave components on the type of gravity anomalies used. In particular, the problem of the determination of indirect effect in geoid undulation was discussed. Numerical tests showed the need of using the exact formula for calculating the indirect effect only in mountainous areas of Poland.
Wojciech Janusz
Examination of deformation of foundation in the course of its displacement
In order to determine vertical deformations of monolithic surface of foundation plate a set of benchmarks is stabilized at the places agreed with geotechnique and construction specialists. For these benchmarks vertical displacements dHi (or ΔZobs according to notation in the work [Prószyński, Kwaśniak, 2006]) are determined using method of the repeated leveling measurements. Displacement of each benchmark consists of two parts:
- dHI + νdHi part caused by vertical displacement and change of inclination of foundation plate without change of its shape
- -νdHi part caused by vertical deformations of foundation plate at benchmark places.
If vertical deformations νdHi of all benchmarks are within limits of accuracy of differences of dHi displacements, in practice one can assume, that shape of foundation plate was in conformity with the model of stiff plate.
Calculation of νdHi value is done through solution of set of observation equations, using method of the least squares. The equations are of the type:
dHi + νdHi = -xidφx - yidφy + dH0
where: xi, yi – horizontal coordinates of benchmark with i number,
dH0 , dφx , dφy – parameters of vertical displacement of foundation plate without change of its shape.
In most cases the set of equation to be solved concerns dHi observations for all benchmarks stabilized on the foundation.
In this work the author justified the assumption, that in case when geotechnique or construction specialist estimated, that base under foundation can be at some places weaker or stronger, which can have impact on local anomalies of -νdHi displacements of benchmarks stabilized in these places, then the measured dHi displacements of these benchmarks should be excluded from calculations of vertical displacement of foundation plate using method of the least squares. According to this assumption -νdHi displacements of benchmarks located in zones of greater deformations of foundation should be calculated later with the use of displacement parameters computed on the basis of solving set of equations solely for these benchmarks, which are outside anomaly zones of foundation.
In this work the author included calculation example using data taken from work (Prószyński, Kwaśniak, 2006), which confirms that the proposed procedure is right. This procedure contributes to improvement of determining parameters of displacements of foundation plate, thus revealing in a better way its increased deformations in the appointed anomaly zones.
Jan Ziobro
Conditions of designing aerotriangulation with non-signalizedcontrol points
Author presented in the article conditions of designing block aerotriangulation with measurement of projection centres and non-signalized control points. The impulse to these studies was given by the results of analysis of 38 blocks elaborated in Poland, which revealed, that contractors applied in designing not entirely precise assumptions. Also domestic technical instructions in this field do not determine goals of designing precisely and comprehensively. Publications related to designing of aerotriangulation concern blocks of non-signalized control points; hence conclusions on accuracy of results and reliability of measurements in network cannot be fully applied to blocks with non-signalized control points.
The aim of study was to determine assumptions for designing aerotriangulation of rectangle blocks at scales of 1:13 000 and 1:26 000, which have been applied in the last period most frequently in our country. In these study the required reliability of measurements was determined, as well as possible accuracy of the results, taking into account precisions of particular groups of measurements achieved in production.
Investigations were carried out comparing results of different variants of aerotriangulation. These variants were created through simulation of measurements and simulation of block adjustment. The applied simulation enabled to evaluate variant of aerotriangulation using the following parameters: global redundancy of network, local redundancy of particular measurements, global redundancy of groups of measurements, mean errors of unknowns, average errors of groups of unknowns.
The detailed goals and scope of the studies were as follows:
- Determination of impact of number of tie points between strips on reliability of particular groups of measurements and accuracy of unknowns and selection of the best number of ties. Variants of aerotriangulation with number of six-fold tie points from 1 to 6 points were analysed.
- Determination of relation between accuracy of the results, reliability of groups of measurements versus distribution and number of ground control points, including selection of the best control network. Six variants of control network were analysed, taking into account accuracy of the results and its homogeneity, as well as reliability of measurements.
- Preparation of additional control points for compensating partial lack of measurement of projection centres (which happens quite frequently). Impact of lack of measurements was studied for 1 to 4 strips.
Author presented in the article conditions for determining the best variant of aerotriangulation, considering reliability of measurements, as well as accuracy and homogeneity of the results. The determined parameters of designing can be a basis for high-quality standard aerotriangulation for these types of blocks.
Janusz Ostrowski
Cartographic concept of maps of land usefulness forcultivating energy plants
Authors presented in the article methodical assumptions concerning cartographic concept of maps of land usefulness for cultivating energy plants. The concept has been prepared with the use of computer-aided techniques, applying spatial data contained in the database of marginal soils and cultivation requirements for energy plants, available in literature.
The prepared cartographic concept, its verification and results of the works allow to conclude, that database of marginal soils and processing system enable extension of its application after adaptation supplements, resulting from the methodical assumptions. Generated thematic maps confirm achievement of the planned visual effect, while keeping dominant role of thematic content, readable information on agricultural land usefulness and possibility of reliable location of areas predestinated for cultivating energy plants. The prepared thematic maps fulfill user expectations, informing at regional scale about location of land, which is potentially useful for cultivating energy plants and at the same time indicating spatial distribution of complexes of agricultural land usefulness, which reflect production potential of agricultural areas.
Albina Mościcka, Małgorzata Brzezińska
Implementation of changeability of features of biblicalgeographic objectsin time-spatial information system
Authors present in the article proposal of time-spatial description of features of geographic objects, which appear in the Bible. Geographic biblical object is characterized by features, which were changed of modified through thousands of years. Multiple sources of knowledge deliver information about such objects, which is different or with various level of reliability.
An attempt to define and make systemic information on biblical objects, in order to enable its implementation in spatial information system, was undertaken in the article. It was assumed, that time-spatial geographic object is biblical geographic object, which in various time periods could have different location or attributes. Form of a given geographic object, i.e. the determined geographic location with attributes in any time period was defined as state of object in this time interval. Features of objects which are constant and those which are time-dependent, were indicated. Features of objects, but also relations between them were presented. The way of description of changeability of object’s geographic location in time was also proposed.
Definition of changeability of features of geographic object was a basis for determining, which features (and it what way) should be included into the system. It initiated preparation of architecture of database of biblical geographic objects, which is a component of time-spatial geographic information system. The system is managed as an internet application, composed from two parts: server application and client application. Server application was prepared with the uses of PHP scripts, while client application was programmed in Flash – Action Script.
The presented examples show, in what way the tables, containing information on components of biblical geographic objects: spatial location, time and attributes, are defined. They also demonstrate, in what way the particular geographic objects were entered into the system