ENGLISH

4卷/4期

4卷/4期

華藝線上圖書館

Pages:

1-12

論文名稱

近景攝影測量中人造標點的自動辨識與定位

Title

Automatic Identification and Positioning of Artificial Targets for Close-range Photogrammetry

作者

王聖鐸

Author

Sendo Wang

中文摘要

由於數位攝影測量的發展,近景攝影測量也朝自動化邁進。近景攝影測量中常以人造標點為施測目標,傳統人工量測方式不但費工且費時。如今在數位影像中自動定得人造標點的像片坐標的技術已行之有年,然而這些系統只定位而不認標,所以定出來的坐標不能與地面標點直接產生關連,也無法與重疊像片之標點直接產生共軛關係。本文所提的方法不但能自動定位,同時能辨識標號,其過程大略分為搜尋標點、標點定位、及標號辨識。利用特別設計的人造標點,結合電腦視覺領域中影像處理的技術,分別以圓形標偵測元搜尋影像中的標點、以最小二乘匹配將標點定位、再利用標準化互相關係數的計算來辨識標號。依此程序設計出一套自動化的程式,並以數位像機實際拍攝三種環境下的標點:單純背景、階梯、與傾斜拍攝加以實驗。結果證實在單純背景下的確可以得到相當滿意的成果,而在階梯和傾斜 30°以下時的成果也尚可接受。

Abstract

Due to the advance of digital photogrammetry, close-range photogrammetry steps into the door of automation. In close-range photogrammetry, artificial targets are frequently used for measurement. It was inefficient and time consuming in the past when there is no choice but manual measurement. Nowadays, automatically determining the photo coordinates from a digital image has been applied for years. However targets are just positioned but not identified by the current systems. Therefore, the positioned targets in an image are not directly associated with the ground targets and the conjugate target points in other overlapped images. This paper proposes an approach to position targets and recognize the identifications of the positioned targets as well. The work can be divided into three steps: searching, localization, and identifying targets. First we designed a special target which consists of two digits and two round-shape targets. Then an ad hoc circular-target detector is used to search all possible round-shape targets in the image. The centers of the detected circular-targets can be precisely located by using the least squares matching. Based on the known relationship between the two digits and the two circular targets, the boundaries of the digits can be determined. Extracting the subimage of the digits and calculating the normalizeιcross correlation coefficients with the standard templates then the digits could be identified. To verify the proposed method, we conducted three experiments The first experiment is to identify targets in an image with uniform white color background. All the targets were successfully and correctly identified in this experiment. The second experiment is designed to find targets in different scales, so that several sets of targets attached in the vertical sides of stairs were imaged and tested. Targets tend to be misinterpreted when their scales are getting small. The third experiment is designed to identify targets in an oblique image. This experiment shows that correct results can be obtained when the image angle is less than 30 degrees.

關鍵字

數位攝影測量、近景攝影測量、圓形標偵測元、自動化、辨識、定位

Keywords

Digital photogrammetry, Close-range photogrammetry, Circular-target detector, Automation, Identification, Positioning

附件檔名

華芸線上圖書館

N / A

備註說明

199912-4-4-1-12

Pages:

13-23

論文名稱

利用植被覆蓋之反射比光譜估測水稻之生長

Title

Estimation of Rice Growth from Reflectance Spectra of Vegetative Cover

作者

蘇慕容 , 楊純明

Author

Muh-Rong Su , Chwen-Ming Yang

中文摘要

本文為一項為期三年試驗之研究成果報告,目的旨在探討利用地面遙測之植被覆蓋反射比光譜於估測水稻生長之可行性,並試予模式化兩者關係。田間試驗係在座落於臺中縣霧峰鄉(北緯 240 02' ,東經 120040' ,海拔高度85m) 之行政院農業委員會農業試驗所農場進行,栽培季節涵蓋 1996 年至1998 年之一、二期稻作,參試品種為臺農 67 號 (Oryza sativa L. cv. Tainung 67)。根據試驗結果,由典型的水稻植被反射比(或稱反射強度)光(波)譜發現不同波長(段)具有不等反射比,且不同生育階段之表現亦不相同。綜合水稻六期作全生育期植被反射比光譜曲線,經一次微分及光譜波峰與波谷轉折點比對,選取波長 554、674 (RED) 及 754nm (NIR) 為三特徵波長。此三波長在生育期間呈二次曲線趨勢,其中 554 及 674nm 波長反射比由生育初期高比值下降至近抽穗期達低點,再隨稻株成熟而上升; 754nm 波長反射比變化則反之。標準差植被指數 (或稱規整差植生指數, normalized difference vegetation index,NDVI) 乃藉由 674 及 754nm 波長計算,全生育期之變化亦呈二次曲線趨勢,其中一、二期作決定係數 (R2 ) 分別為 0.919 及 0.931。試驗又發現,水稻植被外觀物理徵狀與 NDVI 呈現指數關係,依決定係數高低分別為葉面積指數 (LAI) 0.811、葉片數 (LN) 0.809 及葉片乾重 (LDW) 0.669。由此一高決定係數之指數相關結果顯示,吾人可利用植被覆蓋之反射比光譜於水稻生長之估測,尤其是 LAI 與 NDVI 之相關。

Abstract

A three-year study was carried out to develop a model for estimation of rice growth from ref1ectance spectra of ground vegetative cover. Field measurements were conducted at the experimental farm of Taiwan Agricultural Research Institute, Council of Agriculture at Wufeng, Taiwan (240 02'N, 120040'E, elevation of 85m) during the first and the second cropping seasons in 1996, 1997, and 1998. It showed that the typical curve of reflectance spectrum of rice vegetative cover (canopy) has a differential reflectance pattern in the varied wavebands as well as in different growth stages. By using the first order differentiation in cope with peaks and valleys observations from spectral waves, three characteristics wavelengths of 554, 674 (RED), and 754nm (NIR) were selected from turning points of reflectance spectra. Their seasonal changes were curvilinear ref1ectances of 554 and 674nm fell off to the lowest near heading and then climbed up as plants reached maturity; the trend was reversed for the near-infrared reflectance Seasonal changes of normalized difference vegetation index (NDVI) show a similar curvilinear shape in both First (R2 = 0.919) and Second (R2 = 0.931) crops from 1996 to 1998. Relations of the measured physical growth characters and NDVI were exponential, the determining factors (R 2) were 0.811, 0.809, and 0.669 for leaf area index (LAI) leaf number (LN), and leaf dry weight (LDW), respectively. The exponential curves estimate fairly accurately the advancement of growth characters from spectral transformation (NDVI), especially LAI.

關鍵字

水稻、反射比光譜、植被覆蓋、物理生長徵狀、植被指數(植生指數)

Keywords

Rice, Ref1ectance spectrum, Vegetative cover, Physical growth character, Vegetation index

附件檔名

華芸線上圖書館

N / A

備註說明

199912-4-4-13-23

Pages:

25-37

論文名稱

利用 SAR 衛星影像偵測台灣灘海底地形之研究

Title

The Research of Sea Bottom Topography Detecting in Taiwan Shoal by Sar Image

作者

鐘炯陽 , 許明光 , 劉倬騰 , 徐月娟

Author

Jeong-Tang Jong , Ming-Kuang Hsu , Cho-Teng Liu , Yueh-Jiuan G. Hsu

中文摘要

在中低風速及強大潮流的條件之下,淺海地區的海底地形可顯現於雷達影像上,側視空載雷達 (Side Looking Airborne Radar, SLAR)、真實孔徑雷達(Real Aperture Radar, RAR) 及合成孔徑雷達 (Synthetic Aperture Radar, SAR) 等都曾獲得此類影像。台灣灘的位置在澎湖群島西南方,為一面積約 10000 平方公里的廣大沙波 (sandwave) 區域。本研究主要應用流體動力模型、 SAR 成像原理並輔以海研三號現場實測之水深資料、中央氣象局實測風速資料及推算之流速來推算海底地形並與實測水深的海底地形比對。研究的結果顯示推算之海底水深與實測水深趨勢相當吻合。對於中大尺度海底地形的測繪、水深變化監測等實際應用,可考慮本文所使用的方法,未來若可精進至二維模型,應用層面將更為廣泛。

Abstract

Under mid-low wind and strong current conditions, the sea bottom topography in the shallow water can be showed on the radar images. These kind of images had been observed on side looking airborne radar (SLAR); real aperture radar (RAR); and synthetic aperture radar (SAR) images. Taiwan Shoal is a wide sandwave area of 10,000km2 in the south-west of Peng-Hu island. In this thesis, the model proposed by Alpers and Hennings (1984) was applied. Water depth measured by Ocean Research III; calculated current field and wind speed measured by anemometer in Dong-Ji island are used as input data. And the comparison between the model estimated result and the ship-measured depth are made. The comparison shows a good agreement between model and in-situ measurement. And the further efforts for two dimensional model can make the method more useful.

關鍵字

海底地形、台灣灘、合成孔徑雷達 (SAR)

Keywords

Sea bottom topography, Taiwan shoal Synthetic aperture radar (SAR)

附件檔名

華芸線上圖書館

N / A

備註說明

199912-4-4-25-37

Pages:

39-53

論文名稱

「科技短文」植生指數在集水區內的地文分佈研究

Title

Geomorphologic Distribution of Normalized Difference Vegetation Index (NDVI) in Watersheds

作者

劉治中 , 蕭國鑫

Author

Chi-Chung Lau ,Kuo-Hsing Shiao

中文摘要

本研究以福山、七家灣、三地門及立山四集水區的 Landsat TM 及 DTM 資料,利用 Minnaert 方法修正原始遙測資料的地形效應後,計算 NDVI 值,研究其因坡度、坡向、高程、累積流量及地形指數等地文因子引起的地理分 佈變化,結果顯示坡向強烈影響 NDVI 分佈,高 NDVI 值像元較集中於東南方,而且可分成向陽及背陽區,坡度之影響較不明顯,但四區皆顯示 30° ~ 40° 坡度有最大 NDVI 值,在低高程區 NDVI 隨高程而漸增,而相對高海拔區 NDVI 因高程而漸減,可能與河谷位置或溫度變化有關,累積流變為像元在坡面位置的指標,四集水區的 NDVI 都沿坡面位置漸往下坡面而減少,地形指數與 壤表層濕度有關,結果顯示在地形指數大於零的情形下,NDVI 隨地形指數增加而漸減少。

Abstract

Landsat TM data in Fusan, Chichiawan, Sandiman and Lisan watersheds are used to study the affection of geomorphologic factors (aspect slope, elevation, flow accumulation, topographic index) to the geographic distribution of normalized difference vegetation index (NDVI). Raw Landsat TM data are corrected by Minnaert model to mitigate topographic effect. Geomorphologic factors are calculated by Digital Terrain Model. Results show that aspect strongly affect distribution of NDVI. High NDVI pixels appear on south-east aspect. Slopes can be divided into of illuminate and non-illuminate side. Slope angle has comparative low affection to NDVI, but all the data show a peak value in 30° ~ 40° . NDVI increase with elevation in low altitude area, and decrees with elevation in the area higher than 3,000m. Flow accumulation (FAC) value indicating pixel position is either near ridge or bottomland. It helps to find a fact that highest NDVI is on ridge pixel and then decrees toward bottomland along a slope. The topographic index is believed to relate to topsoil moisture content. NDVI are decrees with topographic index in all basins in positive index case.

關鍵字

植生指數、地形效應、地文因子

Keywords

Normalized difference vegetation index, Topographic effect, Geomorphologic factor

附件檔名

華芸線上圖書館

N / A

備註說明

199912-4-4-39-53

更多活動學刊