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1

The process of map calibration and its impact on the quality and accuracy of cartographic materials

Klapa P.

Geomatics, Landmanagement and Landscape

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2018

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no. 1

33--43

EN

The calibration process is a procedure that enables adjusting the scanned portion of the map to the current frame of reference, and equipping it with cartometric properties. As a result of the said process, the raster image becomes cartographic material that can be applied, among others, to the context of geodetic work. There are numerous methods of image transformation and ways of selecting the control points, according to which this process can be carried out. In the paper, the authors present the literature review featuring various problems related to the map calibration process, as well as the methods of transformation, and the ways of selecting the control points. The work was carried out in reference to the example of scanned fragments of cadastral maps, which were then subjected to calibration processes using crosses of map graticule lines and based on situational details. The calibration process was carried out several times using a different number of adaptation points while changing their location and the manner of selection.

2

Edge effect and its impact upon the accuracy of 2D and 3D modelling using laser scanning

Klapa P., Mitka B.

Geomatics, Landmanagement and Landscape

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2017

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no. 1

25--33

EN

The edge effect is a measurement error resulting from the reflection of the laser beam on the adjacent walls, or by its breaking on the edges. Coordinates of points in such cases are determined by averaging the measurements in several areas, resulting in their incorrect positioning in space. Corner points are determined with the same accuracy as the other (flat) elements of the scanned object. This effect is frequently mentioned in publications, which typically state the reasons and mechanisms of the error thus occurred. However, there is a lack of specific examples, showing the impact of the edge effect on the quality and accuracy of geodetic and cartographic reports. In this paper, the authors present sample case studies of the 2D and 3D representation of the test object. The selected corner elements, as well as the vector elements fitted into a cloud of points, show the discrepancy between the breaking points in the drawing (model), and the curved surface of the point cloud. On the basis of the known geometry of the building, distances were determined between the corner points and their representatives on the cloud. In this way, we were able to determine the accuracy of corner points’ presentation by means of the cloud of points, and therefore, we were able to determine the size of the edge effect in specific cases.

PL

Efekt krawędziowy jest błędem pomiarowym wynikającym z odbicia wiązki promienia laserowego na sąsiednich ścianach, bądź poprzez załamanie jej na krawędziach. Współrzędne punktów w takich wypadkach zostają wyznaczone poprzez uśrednienie pomiarów w kilku miejscach, co skutkuje ich błędnym położeniem w przestrzeni. Punkty narożne nie są wyznaczane z tą samą dokładnością co pozostałe (płaskie) elementy skanowanego obiektu. Efekt ten jest wielokrotnie wspominany w publikacjach, w których podawane są powody oraz mechanizmy powstawania tego błędu. Brakuje jednak konkretnych przykładów przedstawiających wpływ efektu krawędziowego na jakość i dokładność wykonywanych opracowań geodezyjno-kartograficznych. W niniejszej pracy autorzy przedstawiają przykładowe opracowania 2D i 3D obiektu testowego. Zaznaczone elementy narożne, a także wpasowane w chmurę elementy wektorowe, przedstawiają rozbieżności pomiędzy załamaniami rysunku/modelu, a zaokrągloną powierzchnią chmury punktów. Na podstawie znanej geometrii budynku zostały wyznaczone odległości pomiędzy punktami narożnymi a jego reprezentantami na chmurze. W ten sposób zostaje określona dokładność przedstawienia punktów narożnych przez chmurę punktów i tym samym wyznaczenie wielkości efektu krawędziowego w konkretnych przypadkach.

3

Application of terrestrial laser scanning to the development and updating of the base map

Klapa P., Mitka B.

Geodesy and Cartography

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2017

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Vol. 66, no. 1

59--72

EN

The base map provides basic information about land to individuals, companies, developers, design engineers, organizations, and government agencies. Its contents include spatial location data for control network points, buildings, land lots, infrastructure facilities, and topographic features. As the primary map of the country, it must be developed in accordance with specific laws and regulations and be continuously updated. The base map is a data source used for the development and updating of derivative maps and other large scale cartographic materials such as thematic or topographic maps. Thanks to the advancement of science and technology, the quality of land surveys carried out by means of terrestrial laser scanning (TLS) matches that of traditional surveying methods in many respects. This paper discusses the potential application of output data from laser scanners (point clouds) to the development and updating of cartographic materials, taking Poland’s base map as an example. A few research sites were chosen to present the method and the process of conducting a TLS land survey: a fragment of a residential area, a street, the surroundings of buildings, and an undeveloped area. The entire map that was drawn as a result of the survey was checked by comparing it to a map obtained from PODGiK (pol. Powiatowy Ośrodek Dokumentacji Geodezyjnej i Kartograficznej – Regional Centre for Geodetic and Cartographic Records) and by conducting a field inspection. An accuracy and quality analysis of the conducted fieldwork and deskwork yielded very good results, which provide solid grounds for predicating that cartographic materials based on a TLS point cloud are a reliable source of information about land. The contents of the map that had been created with the use of the obtained point cloud were very accurately located in space (x, y, z). The conducted accuracy analysis and the inspection of the performed works showed that high quality is characteristic of TLS surveys. The accuracy of determining the location of the various map contents has been estimated at 0.02-0.03 m. The map was developed in conformity with the applicable laws and regulations as well as with best practice requirements.