地面三維雷射掃描儀影響精度因子之研究

Abstract

地面三維雷射掃描儀(地面光達)是一種能在短時間內快速獲取大量高精度三維相對坐標點的儀器，然而進行戶外實地掃描作業時，常會受到許多外在環境因素的影響，例如距離長短、角度不同、物體表面顏色、材質、作業環境溫度、濕度及壓力等，皆有可能影響三維點雲資料之精度。實地掃描作業時，也需整合多個測站的點雲資料時，不同測站的點雲資料因具有不同的參考坐標系統，點雲的連結或坐標系統間的轉換關係，都是造成資料誤差的來源。 本研究探討地面三維雷射掃描儀其目標物顏色因子對反射強度及精度之影響，探討顏色與強度值的關係，以及分析強度值對精度之影響。接著探討被掃描物在不同距離造成的影響、儀器架設產生的問題、控制點分布造成的影響以及點雲資料坐標轉換後的實際問題。經本文實驗後提出一個合適的坐標轉換方式，對儀器存在的系統性誤差以及隨機誤差加以改正。 地面三維雷射掃描儀掃描出來的點雲資料會因為量測環境而產生雜訊，故本文使用常用的雜訊濾除方法，比較各種濾除方法的精度表現。另外本研究中將自製反射標加入實驗，求得更好的反射標定位精度，並比較定位精度差異。

ABSTRACT Terrestrial LiDAR is the kind of instrument that can obtain massive amount of information on high-precision for relative 3-D coordinates. However, when conducting outdoor scanning operation at the site, the instrument can be exposed to influence from several environmental factors, such as distance, angle, surface color of object, material, environmental temperature, humidity, and pressure, and it is likely that change can be made to precision of data. Besides, when it is to integrate data from several observation stations, data from various observation stations is found with diverse referential coordinate system, so that it would result in error of data connection or coordinate systems transformation. This study would investigate the impact of color factor of target on reflection intensity and precision for the scanner as it explores the relationship between color and intensity as well as analyzes the impact of intensity value on precision. Then, it would look into the impact of objects scanned as resulted from different distance, impact resulted from instrument installation or distribution of control points, and the actual problem after the transformation of information coordinates. With experiment in this study, it would then put forth an appropriate way of coordinate transformation that can help rectify the systematical error existent with the instrument. As for data of scanner, since the environment where instrument is will generate noise, it is why this article has made us of various ways for noise elimination. In addition, self-made reflection coordinates are added into the experiment so that positioning of reflection coordination can be made more precise and it can work to compare the difference of positioning precision.