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Maapealse laserskaneerimise geomeetria mõju punktipilve müra tasemele

Veia, Kristjan (2016) Maapealse laserskaneerimise geomeetria mõju punktipilve müra tasemele. [thesis] [en] Influence of scanning geometry on the noise level of a point cloud..

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Abstract

Pidevalt kiirenev elutempo seab ka geodeesiale piiranguid ning uusi ületamist nõudvaid takistusi. Projekteerijad ning ehitajad otsivad aina rohkem uusi viise oma töö kvaliteeti tõsta, seetõttu peab geodeesia liikuma sama kiiresti või kiireminigi edasi, et mitte takistada progressi. Sel hetkel sõltub skaneerimine suuresti veel füüsikaseadustest, ning meil tuleb arvestada erinevate nähtustega nagu divergents, langemisnurgad ja näiteks atmosfääri tingimused, kuid hetkese lasertehnoloogia arenguga võib arvata, et ka nende mõju pigem väheneb. Kuna hetkel on andmetöötlusele kuluv aeg veel üsna suur, siis võikski tulevikus näha kohapealset andmetöötlust, ehk esialgset punktipilve registreerimist mõõdistataval objektil. Käesoleva lõputööga anti ülevaade laserskaneerimise vigade analüüsist ja nende tekkepõhjustest. Võrreldi kahte erinevat tüüpi laserskanneri andmeid võimalikult samalaadsetes tingimustes. Kasutati Faro X330 ja Leica Scanstation C10 laserskannerit. Andmete iseärasusi võrreldi kasutades liitmõõtemääramatuse ning tasapinna sobitamise võrrandeid. Töös käsitleti punktipilve töötluse meetodeid, toodi välja erinevad punktipilve kasutusvaldkonnad, anti põgus ülevaade andmete töötlemise programmidest, sealhulgas Faro Scene, Leica Cyclone. Lõputöö eesmärgiks oli välja selgitada langemisnurga mõju punktipilve müra tasemele. Lõputöö käigus tuvastati selge müra suurenemine langemisnurga suurenemisel, mis tähendab, et kirjanduses levivat arusaama üle 60 kraadise langemisnurga mõjust võib pidada tõeseks. Lisaks tuvastati erinevus kahe laserskanneri vahel, nimelt ca. 79 kraadise langemisnurga puhul on tasapinna võrrandi sobitamise tulemusel saadud Leica C10 standardhälbed väiksemad Faro X330-st, olles seni olnud paralleelse kasvusuunaga. Lisaks arvutati ka mõlema laserskanneri puhul z-koordinaadi teoreetiline mõõtemääramatus. Erinevatest tootjapoolsetest täpsuslikest näitajatest tingituna on graafikud plaatide raames erinevad. Faro X330 puhul on kõrgusliku mõõtemääramatuse kasv nähtav 72-83 kraadise langemisnurga korral, olles eelnevalt langenud alates 38,7 kraadisest langemisnurgast. Kogu mõõtemääramatuse vahemik on 0,93-2,17 mm. Sarnaselt Farole on Leica kõrguslik mõõtemääramatus langevas trendis, kuid murdepunkt, kus langus läheb üle tõusuks on 80 kraadi juures. Leica C10 mõõtemääramatuse vahemik on 0,9-2,25 mm. Mõlema instrumendi puhul on selgelt arusaadav madalkoht mõõtemääramatuses, ehk siis koht kus peaks olema mõõtmiste võimalik diapasoon kõige väiksem, Farol 71,8 kraadise langemisnurga juures ning Leical 79,9 kraadise langemisnurga juures.

Abstract [en]

A constantly accelerating pace of life imposes limitations and obstacles that require overcoming to geodesy. Designers and builders are more and more looking for new ways to improve the quality of their work, which is why geodesy must develop as fast or even faster in order to avoid impeding the progress. At the moment, laser scanning is very much dependent on the laws of physics, and we must take into account various phenomena, such as divergence, incidence angles and atmospheric conditions, but considering the current development of laser technology, it may be expected that their impact will decrease. Since presently, the time spent on data processing is still quite large, we could foresee an on-site data processing in the future, i.e. the initial registration of point cloud on the measured object. This thesis gave an overview of error analysis of laser scanning and the causes of such errors. The data of two different laser scanners were compared in as similar conditions as possible. For this, Faro X330 and Leica Scanstation C10 laser scanners were used. The particularities of the data were compared, using the combined uncertainty of measurement and surface area matching equations. In this thesis, the methods of point cloud processing techniques were examined, various uses of point cloud were pointed out, and a brief overview of data processing programs, including Faro Scene, Leica Cyclone, etc. was given. The aim of this thesis was to find out the impact of incidence angle to the noise level in a point cloud. The thesis revealed that the increase of incident angle brings about a visible increase of noise level, which means that the widespread perception about the impact of the incidence angle of 60 degrees may be considered veritable. Additionally, a difference between the two laser scanners was detected: in case of an incidence angle of approximately 79 degrees, the standard deviation of surface area matching equation of Leica C10 is smaller than the one of Faro X330, having so far had a parallel growth direction. Also, a theoretical uncertainty of measurement of the z-coordinate was calculated for both laser scanners. Due to different accuracy indicators provided by the manufacturer, the graphs of the plates are different. For Faro X330, the growth of uncertainty of height measurement is visible in case of an incidence angle of 72-83 degrees, having previously fallen from an incidence angle of 38.7 degrees. The entire range of uncertainty of measurement is 0.93-2.17 mm. Similarly to Faro, the uncertainty of height measurement of Leica is falling, but the turning point, where the fall turns into a rise, is reached at 80 degrees. For Leica C10, the range of uncertainty of measurement is 0.9-2.25 mm. For both instruments, there should be an evident low point in the uncertainty of measurement, i.e. a point where the possible range of measurements results should be the smallest. For Faro, it's reached at the incidence angle of 71.8 degrees and for Leica, at the incidence angle of 79.9 degrees.

Item Type: thesis
Advisor: Tarvo Mill
Subjects: Construction > Applied Geodesy
Divisions: Institute of Construction > Applied Geodesy
Depositing User: Kristjan Veia
Date Deposited: 27 Jun 2016 07:15
Last Modified: 27 Jun 2016 07:15
URI: http://eprints.tktk.ee/id/eprint/2291

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