ENGLISH

15卷/4期

15卷/4期

華藝線上圖書館

Pages:

307-315

論文名稱

台灣附近海域之衛星測高波形重定資料精度評估

Title

Assessment of Retracked Sea Surface Heights Around Taiwan

作者

高煥欽,郭重言, HyongKi Lee, 沈嗣鈞

Author

Huan-Chin Kao, Chung-Yen Kuo , Hyongki Lee, C.K. Shum

中文摘要

本文之主要目的為進行台灣附近海域之JASON-2 20-Hz和TOPEX/Poseidon(T/P) 10-Hz衛星測高資料波形重定和波形重定演算法之功效評估,並將重定之測高資料與台南安平港驗潮站資料進行比較分析。台灣附近海域海深及海況極為複雜,位於台灣西邊之台灣海峽,其海深均不超過200公尺,而位於台灣東岸之西太平洋海域,其海深可達4000公尺。另外,台灣海峽之海潮潮差較西大平洋大。測高衛星於淺海區域觀測量精度不佳,特別是近海岸處,其主要原為雷達反射脈衝訊號易受到陸地干擾,導致衛星接收之反射波形訊號複雜,因而無法精確求取波形前緣中點,而波形重定(waveform retracking)技術可有效改進此缺點。本研究應用波形重定技術重定台灣附近海域測高資料,應用之波形重定演算法包含Offset Center of Gravity演算法、門檻值演算法(threshold retracker)、改良型門檻值演算法(modified threshold retracker)與冰原演算法(ice retracker),然後分別計算經由不同演算法重定後之資料改善率(improvement percentages, IMPs),用來評估重定測高資料之精度,以求取各研究區域之最佳波形重定演算法。結果顯示波形重定技術可有效提昇T/P與JASON-2衛星之近岸資料精度和數量,其IMP可達到82%,而最佳演算法則因地而異。另外,波形重定後之測高海水面高度與安平驗潮站資料,其變化更加吻合。

Abstract

The purpose of the study is to evaluate the accuracy of the retracked TOPEX/Poseidon (T/P) 10-Hz and Jason-2 20-Hz altimetry sea surface heights (SSHs) around Taiwan by comparing to Anping tide gauge records. The sea state and bathymetry in the study area are highly various. Taiwan Strait located at the west of Taiwan has an average bathymetry less than 200 m and its amplitudes of ocean tides are extremely high. In contrast, the western Pacific Ocean located at the east of Taiwan has deep bathymetry of 4000m and relatively low amplitudes of ocean tides. The measurements of radar altimeters are inaccurate in shallow oceans especially near the coastlines because the displacement of the midpoints of leading edges results from the waveforms returning from ocean-land areas. This disadvantage can be effectively overcome by waveform retracking technique. In this study, retracking algorithms including the Offset Center of Gravity, threshold, modified threshold, and ice retrackers were used and the performance of different algorithms were examined by computing the improvement percentages (IMPs). The result shows that T/P and Jason-2 data can be significantly improved by the waveform retracking with the highest IMP at 82% and the optimal retracking algorithm highly depends on the characteristics of the study area. In addition, the retracked Jason-2 SSHs agree better with Anping tide gauge records than non-retracked data.

關鍵字

衛星測高、波形重定、驗潮站

Keywords

Satellite Altimetry, Waveform Retracking, Tide Gauge

附件檔名

華芸線上圖書館

N / A

備註說明

201012-15-307-315

Pages:

317-324

論文名稱

網形改正GNSS相對天頂向對流層延遲

Title

GNSS Relative Tropospheric Zenith Delay Correction Based on the Network

作者

陳揚仁, 吳究, 謝昀錐

Author

Yang-Zen Chen, Joz Wu, Yun-Chui Hsieh

中文摘要

全球導航衛星系統 (GNSS)在現代已經進入高效能的實際運作階段,然而在GNSS相對定位過程中,有許多誤差會對定位精度造成影響。對於相對定位基線上兩接收儀的觀測量而言,有許多的誤差量是相近似的,如接收器時鐘誤差、衛星時鐘誤差、衛星軌道誤差等;若是長度十公里以內的短基線,兩接收儀所受到之電離層與對流層延遲亦可視為相似的;故可利用二次差分的技術消除共同性的誤差。但是隨著基線長度的增加,兩站之間的電離層與對流層延遲的差異性會漸漸的增加,通常前者可藉由無電離層線性組合消除,後者必須依靠各式模型估計。本研究利用多個參考站,計算求解得各參考站與主參考站之間的相對對流層天頂向延遲,並利用內插技術得到此區域內相對於主參考站之天頂向延遲模型,以期能夠得到更加精確的定位結果。

Abstract

The global navigation satellite systems have been applicable. But in the process of positioning, there are many errors which affect the accuracy of positioning. In a relative position case, many errors of two receivers are similar such as receiver clock, satellite clock and satellite orbit biases. The ionosphere and troposphere delays are also similar if the length of base line is short. Therefore they can be eliminated by a double difference technique.But the longer the baseline is, the more different the ionosphere and troposphere delays will be. The former could be eliminate by linear combination. The latter must estimated by models.This research included several reference stations and determined the relative tropospheric zenith delays between the master and subsidiary reference stations. Then the relative tropospheric zenith delay between the rover station and master reference station was estimated by an interpolation technique. The accuracy of positioning would be improved through the interpolated estimation.

關鍵字

全球導航衛星系統、二次差分、對流層天頂向延遲

Keywords

Satellite Altimetry, Waveform Retracking, Tide Gauge

附件檔名

華芸線上圖書館

N / A

備註說明

201012-15-317-324

Pages:

325-341

論文名稱

以向量式遮蔽偵測為基礎利用空載傾斜攝影進行自動化牆面紋理貼圖

Title

Automatic Façade Texture Mapping using Airborne Oblique Imagery with Vector-based Occlusion Detection

作者

朱展毅, 饒見有

Author

Chan-Yi Chu, Jiann-You Rau

中文摘要

仿真數碼城市在適地性服務上的應用逐日增加,使得仿真數碼城市之建置成為重要的研究課題,然而傳統上採用地面拍攝及空載垂直攝影的方式會造成牆面較嚴重的遮蔽效應及幾何變形問題,而降低仿真數碼城市視覺的效果。因此、本研究建議採用空載傾斜攝影以降低牆面被遮蔽之效應,並針對牆面被建物遮蔽的問題提出一套自動化的處理流程,透過漸進式的篩選機制選擇幾何變形最小之影像來製作牆面紋理貼圖,藉此減少人力介入並提高貼圖製作效率。研究中針對牆面遮蔽問題提出向量式遮蔽偵測演算法來判斷牆面是否有遮蔽區,若有則予以移除並以其他角度之影像重建牆面應有之紋理資訊。實驗結果顯示,本研究提出之演算法可全自動的產生牆面紋理貼圖,且有效地將牆面遮蔽效應最小化,而所產生的紋理貼圖,其品質也多能滿足大部分仿真數碼城市的應用。

Abstract

Due to the application of cyber city are getting more and more, the generation of a photo-realistic cyber city is becoming an important research topic. Conventionally, the pictures taken on the ground or by vertical aerial imaging will introduce serious occlusion effect and geometric distortion, thus will degrade the visual effect of a photo-realistic city model. In this paper, we thus propose an automatic scheme for facade texture mapping according to a mechanism for the selection of better imaging geometry for the purpose of reducing human interference and increasing the texture quality. In the research, the occlusion problem is solved by means of a vector-based occlusion detection algorithm. In case of occlusion, it will be removed and restored from the other images taken from other viewing positions. Experimental results demonstrate that the proposed scheme can automatically generate the facade texture information when occlusion effect occurred. The texture quality can satisfy most of the cyber city application as well.

關鍵字

數碼城市、牆面貼圖、向量式遮蔽偵測、無縫鑲嵌、空載傾斜影像

Keywords

Cyber City; Façade Texture Mapping; Vector-based Occlusion Detection; Seamless Mosaicking; Airborne Oblique Imagery

附件檔名

華芸線上圖書館

N / A

備註說明

201012-15-325-341

Pages:

343-366

論文名稱

多重影像匹配於房屋模型重建

Title

Multiple Images Matching for 3D building Modeling

作者

黃祐祥, 陳良健

Author

Yu-Hsiang Huang, Liang-Chien Chen

中文摘要

三維地理資訊系統為了描述現實世界,常使用物空間環境特徵。其構成元素包含房屋、道路、植被等,其中房屋為最顯著者。重建三維房屋模型,最常見的資料來源之一為航照影像。使用航照影像重建三維房屋模型,處理過程分為三大部分:房屋偵測、影像匹配及模型重建。本研究結合多航帶高重疊數位航照影像,進行房屋模型重建,處理重點為多重影像匹配及模型重建。處理屋頂形狀包含山型屋、女兒牆房屋及具有屋頂副結構之平頂屋。研究中在主影像中概略圈選房屋工作區,利用輪廓特徵偵測房屋資訊,以便後續影像匹配。利用多重影像匹配技術來搜尋共軛特徵,經由二維特徵的線追蹤並加入三維資訊進行判斷,得到三維房屋邊緣線段,配合著利用房屋特徵點所偵測出屋頂內部資訊進行房屋模型重建。實驗成果顯示,多重影像匹配有效提升匹配精度,利用屋頂面資訊也可改善模型高程精度,房屋模型與參考資料相比,三軸方向之RMSE可達40公分內。

Abstract

Three dimensional geographic information systems describe the reality with environmental elements such as buildings, roads, vegetation etc. Among those elements, building is the most prominent. Aerial images are commonly used in building reconstruction. In building reconstruction with aerial images, building detection, image matching and building modeling are the three major works. This study uses multiple strips acquired from highly overlapped aerial images to perform 3D building modeling. Multiple image matching and building modeling are the major works in this study. Test cases include different types of building roofs. We first select the working area in the master image to extract building features. Then, the detection of building information with line features can aid the image matching. Multiple image matching employs multi-windows with multi-epipolar constraint to find conjugate positions in the same procedure. In the generation of line segments, line tracing is performed in the image space with 3D information. Building modeling is made by the integration building boundaries and roof surface information. The results show that multiple images matching can improve the matching accuracy. Model refinement with 3D roof point clouds can work well. Compared with reference data, the RMSE of building model in most of case can be smaller than 0.4m.

關鍵字

房屋重建、多重影像匹配、多視窗匹配、整合式匹配

Keywords

Building reconstruction, Multiple images matching, Multi-eipolar matching, Multi-windows matching

附件檔名

華芸線上圖書館

N / A

備註說明

201012-15-343-366

Pages:

367-374

論文名稱

面陣列FLIR-T360熱影像特性之研究

Title

Research on Characteristic of Area-Based Thermal Infrared Images

作者

那至中, 黃灝雄

Author

Chih-Chung Na , Hao-Hsiung Huang

中文摘要

熱紅外波段因不受日夜條件限制,在遙感探測中佔有相當重要的地位。在判釋遙測影像之前,通常必先確定各波段影像的幾何性質一致,使影像受儀器本身的影響減到最低。本研究以FLIR-T360紅外線熱像儀為研究對象,探討熱像儀的成像特性,且嘗試率定與改正蒐集之熱影像。率定熱像儀的實驗可分為幾何與輻射兩方面,幾何方面使用改良型的實地率定法,以求取熱像儀的內方位參數;輻射方面則使用實地調查法,求得控制點溫度,利用拍攝控制點蒐集多筆資料,擬合出輻射改正模型;本文另展示熱影像幾何以及輻射改正後的成果,並說明綜合幾何與輻射特性之熱陰影效應。

Abstract

Thermal infrared data is important when conducting remote sensing investigation, for it could be acquired both in day and night. The change of temperature has characteristic significance of representation. So the thermal infrared images are used not only in the domain of surveying, but also in the environment monitoring, the urban development, and the disaster prevention. Before interpreting the remote sensing data, one would make sure that each image of bands has similar image geometry. Calibrating such geometry could prove that the effect from the lens distortion had been minimized. In such case, calibrated thermal images are necessary to guarantee that the image coordinates can be registered to the image coordinates of the other bands. A thermal sensor, FLIR-T360 has been calibrated in this research. Two aspects of calibration executed are geometric and radiometric. A conventional calibrated template has been improved for using in the geometric calibration. The thermal sensor’s interior orientation elements were then found by using a field method. In the radiometric aspect, in situ method has been employed to determine temperatures of the chosen control points. The results of correction in geometric and radiometric aspect are also shown and discussed in this study.

關鍵字

面陣列熱像儀、熱紅外影像、率定

Keywords

Area-Based Thermal Sensor, Thermal Infrared Image, Calibration

附件檔名

華芸線上圖書館

N / A

備註說明

201012-15-367-374

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