ENGLISH

23卷/1期

23卷/1期

華藝線上圖書館

Pages:

1-13

論文名稱

影像式空載光達點雲編碼應用於三維建築模型擷取

Title

Image-based Airborne LiDAR Point Cloud Encoding for 3D Building Model Retrieval

作者

陳俋臣、林昭宏

Author

Yi-Chen Chen, Chao-Hung Lin

中文摘要

隨著網際網路2.0技術與數位城市模型建置的發展,愈來愈多三維數位模型的創造者,在網路形式的資料共享平台上分享作品,這些三維數位模型可以應用在許多領域,例如:導航、都市規劃與虛擬實境。以往重建三維建築模型使用的是攝影測量或點雲資料,但為使資源再利用,本文提出一個三維數位模型的擷取系統。首先從網際網路收集約100萬個三維數位模型,接著用空載光達系統獲取的三維建築模型點雲,作為查詢的輸入資料,以擷取資料庫中與輸入資料的幾何形狀相似的三維數位模型,再利用擷取出的三維建築模型,有效率地建造數位城市模型。為了有效地擷取三維數位模型,常見的做法是使用一個幾何形狀描述子,來編碼資料庫中的三維數位模型,這樣的做法適用於使用三維數位模型作為查詢資料。然而我們提出的系統,是利用空載光達點雲作為查詢資料。空載光達點雲具有稀疏、雜訊以及取樣不完整的特性,相關研究的方法無法直接適用於我們的系統,因此我們提出以深度影像和空間直方圖統計為基礎的編碼方式:利用深度影像描述建築物屋頂面的表面起伏,配合幾何特徵的萃取,將幾何特徵透過空間直方圖統計得到的係數,作為編碼結果的表達方式。本研究的編碼方式,可以降低由空載光達點雲資料雜訊衍生的問題,和側面與底面不完整取樣,所帶來的編碼困難度。藉由三維建築模型的細節層次(Level of Detail, LoD)測試,以及三維數位模型資料庫的資料擷取測試,可證本文提出的方法優於其他相關的方法,並說明由空載光達點雲資料的編碼擷取三維建築模型,以建構數位城市模型的可行性。

Abstract

With the development of Web 2.0 and cyber city modeling, an increasing number of 3D models have been available on web-based model-sharing platforms with many applications such as navigation, urban planning, and virtual reality. Based on the concept of data reuse, a 3D model retrieval system is proposed to retrieve building models similar to a user-specified query. The basic idea behind this system is to reuse these existing 3D building models instead of reconstruction from point clouds. To efficiently retrieve models, the models in databases are compactly encoded by using a shape descriptor generally. However, most of the geometric descriptors in related works are applied to polygonal models. In this study, the input query of the model retrieval system is a point cloud acquired by Light Detection and Ranging (LiDAR) systems because of the efficient scene scanning and spatial information collection. Using Point clouds with sparse, noisy, and incomplete sampling as input queries is more difficult than that by using 3D models. Because that the building roof is more informative than other parts in the airborne LiDAR point cloud, an image-based approach is proposed to encode both point clouds from input queries and 3D models in databases. The main goal of data encoding is that the models in the database and input point clouds can be consistently encoded. Firstly, top-view depth images of buildings are generated to represent the geometry surface of a building roof. Secondly, geometric features are extracted from depth images based on height, edge and plane of building. Finally, descriptors can be extracted by spatial histograms and used in 3D model retrieval system. For data retrieval, the models are retrieved by matching the encoding coefficients of point clouds and building models. In experiments, a database including about 1,000,000 3D models collected from the Internet is used for evaluation of data retrieval. The results of the proposed method show a clear superiority over related methods.

關鍵字

點雲編碼、三維模型擷取、空間直方圖統計、數位城市建模

Keywords

Point Cloud Encoding, 3D Model Retrieval, Spatial Histogram, Cyber City Modeling

附件檔名

華芸線上圖書館

http://www.airitilibrary.com/Publication/Index?DocID=10218661-201803-201803260004-201803260004-1-13

備註說明

N / A

Pages:

15-24

論文名稱

利用衛星測高偵測颱風所引起的中尺度氣旋渦

Title

Detecting Cyclonic Eddies Induced by Global Super Typhoons by Using Satellite Altimetry

作者

鄭宜婷、曾若玄、張育嘉、陳昭銘

Author

Yi-Ting Cheng, Ruo-Shan Tseng, Yu-Chia Chang, Jau-Ming Chen

中文摘要

當颱風的行進速度小於該海域的第一斜壓模之相位速度時,定義為緩慢移動,本研究探討颱風在緩慢移動狀態下所造成的表層流場特性,在1993-2015期間全球一共有22個緩慢移動的超級颱風,分析其衛星海面測高資料、衛星追蹤表面漂流浮球與實測海洋水溫剖面數據,發現其中有7個超級颱風促使(或加強)中尺度氣旋渦的產生。這些氣旋渦的特徵比起一般大洋的渦漩更為明顯,其中又以西北太平洋與南太平洋的超級颱風渦漩最強,流速可達2 m/s,渦漩動能達到4800 cm2/s2,存活時間多達8個月。水溫資料顯示,當颱風消失後,氣旋渦結構持續增強且形成湧升流。此外,渦漩動能與颱風行進速度亦呈現負相關性。

Abstract

This study analyzed data from satellite altimeter measurements, satellite-tracked surface drifters and global typhoons from 1993 to 2015 to investigate mesoscale cyclonic eddies induced by slow-moving super typhoons, defined as that the translation speed of typhoon is less than the phase speed of first baroclinic mode in that ocean. Our results show that among 22 slow-moving super typhoons found globally in this period, only seven typhoons produced or strengthened cyclonic eddies (3 in Northern Hemisphere, and 4 in Southern Hemisphere). Comparing to the averaged characteristics of eddies in open oceans, these typhoon-induced eddies had stronger intensity and longer lifespan, especially for the Northwestern Pacific and South Pacific Oceans. Take TC-Nida-eddy for instance, maximum current speeds of over 2 m/s, lifespan of 8 month, temperature drop of 4.5 ˚C and formation of upwelling were observed. A negative correlation is also found between eddy’s EKE and TC’s translation speed.

關鍵字

超級颱風、中尺度氣旋渦、衛星高度儀、表面漂流浮球、絕對動力地形

Keywords

Super Typhoon, Mesoscale Cyclonic Eddy, Satellite Altimetry, Surface Drifter, Absolute Dynamic Topography

附件檔名

華芸線上圖書館

http://www.airitilibrary.com/Publication/Index?DocID=10218661-201803-201803260004-201803260004-15-24

備註說明

N / A

Pages:

25-42

論文名稱

應用Landsat-8影像探討臺中市新社花海節對地區溫度變化之影響

Title

Using Landsat-8 Images for the Impact of Flowery Field on the Land Surface Temperature Change

作者

邱仁德、徐逸祥

Author

Jen-Te Chiu, Yi-Shiang Shiu

中文摘要

現今氣溫的上升、氣候變遷與全球暖化是全球相當熱門的議題。根據研究指出,人為活動導致土地利用改變,是造成地表溫度變化與熱島效應的主因之一。 近年來臺灣舉辦許多季節性質活動,造成活動地區土地利用的變化,同時亦會湧入大量的人潮與車流量,使地表溫度也隨之產生變化。多數人對於熱島效應只會聯想到都市,然而非都市地區的人為活動亦可能造成地表溫度的變化,進而導致地區微氣候的改變,因此本研究針對季節性活動與地表溫度及熱島效應的關係做完整探討與呈現。 本研究採用Landsat-8熱紅外影像,結合遙感探測技術進行地表溫度反演,探討臺中市新社花海節舉辦,對於地區地表溫度及熱島強度的影響,藉由監督式分類法進行地物分類,並給予各自的輻射值,藉由地表溫度反演算式得到研究區域之成果,除了區域性比較,也採用花海季節與非季節的資料,藉此增加時間性比較。 研究結果顯示,在花海季節時期新社地區之地表平均溫度有升高的現象,並且逼近臺中市其他高溫地區,如:大里工業區、臺中火力發電廠,顯示非都市地區的短暫性人為活動及地表覆蓋之變化,可能對地表溫度造成影響。

Abstract

Nowadays the rising of temperature making global warming and climate change becomes very popular topics. Previous studies pointed out that human activity is one of the causes of the heat island effect. In Taiwan, more and more seasonal tourism activities are held in recent years along with the improvement of life quality. However, such activities attract a lot of crowds and traffic flow, and change the heat island intensity. In order to monitor this effect, this study uses thermal infrared channels of Landsat series imagery and retrieves the land surface temperature based on the methodology proposed by Jiménez-Muñoz et al. (2014) and Rozenstein et al. (2014). Xinshe flowery field in Taichung City is chosen to monitor the change of heat island effect during different periods. With supervised maximum likelihood classification, land features are divided into four categories: water, soil, impervious surface and vegetation; and then the emissivity values are assigned to each category. The results show that the land surface temperature of the flowery field has indeed risen during the seasonal activities. Besides, the land surface temperature in the flowery field is as high as other heat areas in Taichung, such as Tali Industrial District and Taichung Thermal Power Plant. This confirms that impacts of changes in land use/cover and human activities may influence the land surface temperature.

關鍵字

地表溫度、Landsat-8、季節活動、土地使用、熱島效應

Keywords

land surface temperature, Landsat-8, seasonal activities, land use, heat island effect

附件檔名

華芸線上圖書館

http://www.airitilibrary.com/Publication/Index?DocID=10218661-201803-201803260004-201803260004-25-42

備註說明

N / A

Pages:

43-59

論文名稱

比較不同移除凹坑演算法於空載光達nDSM

Title

A Comparison of Pit Removal Algorithms for Airborne Laser Scanner nDSM

作者

林志樺、王驥魁

Author

Zhi-Hua Lin, Chi-Kuei Wang

中文摘要

正規化數值表面模型(Normalized Digital Surface Model, nDSM)是由數值表面模型(Digital Surface Model, DSM)減數值高程模型(Digital Elevation Model, DEM)而得,nDSM代表地物與地表間的高程差。DSM通常是以空載光達系統(Airborne Laser scanner, ALS)掃瞄得到之第一回波點雲內插而得。然而在森林中,部分雷射經由孔隙穿透至樹冠層以下,導致部分第一回波並非在樹木表面,這些第一回波導致DSM網格值降低且與鄰近網格有明顯差異,以該DSM所產製的nDSM也會有相同情況。這些不自然且不規則的網格稱作凹坑(Pit),凹坑影響DSM、nDSM的應用與合理性,故需移除。移除凹坑演算法的目的是移除植被上的凹坑,但測區內可能會有植被以外的地物存在,所以本研究的目的為探討四種移除凹坑演算法在植被nDSM與非植被nDSM上的表現。比較不同移除凹坑演算法移除植被凹坑的能力,以及該演算法是否能保留地物表面原始特徵且更合理地展示表面起伏。四種演算法分別為中值濾波(Median filter)、高斯平滑濾波(Gaussian smoothing filter)、帶有樹冠型態控制的填補凹坑演算法(Pit filling algorithm with morphological crown control)、免除凹坑演算法(Pit-free algorithm)。研究成果顯示,帶有樹冠型態控制的填補凹坑演算法、免除凹坑演算法皆能有效地減少森林凹坑數量,並且不會造成樹冠表面過渡平滑。當地物下方中空(孤立木、建物)或結構有許多孔隙(電塔),使部份第一回波低於地物表面,導致地物在DSM、nDSM上起伏不明顯或不合理,免除凹坑演算法是四種方法中唯一能改善此問題的演算法。

Abstract

Normalized Digital Surface Model (nDSM) represents the elevation of the object with respect to the ground surface, which can be obtained by subtracting Digital Elevation Model (DEM) from Digital Surface Model (DSM). The DEM can be obtained by interpolating the elevations of the first returns from the airborne laser scanner (ALS) data. However, in forest area, the laser can penetrate through the openings of the canopy, where the first returns of ALS point clouds are not necessary on top of the canopy. As a result, the DSM interpolated based on the first returns may show lowered elevation values. In turn, the nDSM obtained from such DSM may show similar phenomenon. In DSM and nDSM data, the raster with lowered elevation value is called pit, which need to be removed for the purpose of data integrity. This study compares the performance of four pit removal algorithms, i.e., median filter, Gaussian smoothing filter, pit filling algorithm with morphological crown control, and pit-free algorithm, in vegetated and non-vegetated areas with the focus on pit removal in vegetated area while keeping the surface integrity. The results show that pit filling algorithm with morphological crown control and pit-free algorithm can effectively reduce the number of pits in forest area while avoid creating overly smoothed results. For single tree, building, and electrical tower, only pit-free algorithm can reasonably mitigate the pits in DSM and nDSM.

關鍵字

正規化數值表面模型、空載光達、移除凹坑演算法

Keywords

normalized digital surface model, airborne laser scanner, pit removal algorithm

附件檔名

華芸線上圖書館

http://www.airitilibrary.com/Publication/Index?DocID=10218661-201803-201803260004-201803260004-43-59

備註說明

N / A

Pages:

61-69

論文名稱

以Protégé建立OSM房屋相關標籤之網路本體語言

Title

Web Ontology Language for OSM’s Building using Protégé

作者

張智安、謝旻哲

Author

Tee-Ann Teo, Min-Che Hsieh

中文摘要

開放資料為空間資訊領域重要的發展趨勢,隨著各類資料的開放,各資料集之間的互操作性顯得更加重要,而知識本體(ontologies)可描述一知識概念之邏輯語意,有助資料集的整合應用。開放街圖(OpenStreetMap, OSM)為自願性地理資訊(Volunteered Geographic Information, VGI)中顯著的案例,本技術短文目的為建立OSM房屋相關標籤之網路本體語言。Codescu et al. (2011)將OSMwiki與Taginfo公布之常用標籤組織為OSMonto(OSM ontology),然而近年來OSM三維相關標籤日趨豐富,從過去二維資訊為主逐漸朝向三維化發展,為了與OSM實際標籤使用相符有必要更新OSM本體模型。本研究延續部分OSMonto建立之方法用於建立房屋相關標籤之知識本體,本體論編輯器乃史丹佛大學所開發之開源軟體Protégé,本研究從類別、屬性、物件關係等層面實現房屋相關標籤之層次結構。此外,本技術短文並採用Jena API完成本文建立之OSM房屋知識本體的查詢實作,確認本文建立之OSM房屋知識本體可用性,未來更能透過本體模型提升與其他領域之互通性。

Abstract

Open data is an important trend in different domains. In order to integrate and understand semantic information from different domains, ontology is a good way to descript the concepts in different domains. OpenStreetMap (OSM) project is the most significant example among Volunteered geographic information (VGI). The aim of this study is to develop an ontology-based framework for the building in OSM. OSMonto organized the tags from OSMwiki and Taginfo into an ontology framework in 2011. However, many useful keys and tags are proposed for OSM recently. For example, three-dimensional building information tags (e.g. building=*). OSM’s information becomes richer that is from two-dimensional development to three-dimensional. In order to improve the structure of OSM tags, it is necessary to revise an up-to-date ontology-based framework for OSM. We used an open-source ontology editor, i.e. protégé, to build up the OWL for the building in OSM. This study expected to achieve a hierarchy’s rationalization and definition of tag’s attributes. Furthermore, this ontology can be used in querying via Jena API. This study discussion about the data sources, attribute definition methods, and the hierarchy of key value that the OSM can be used to exchange with other domain ontology easier.

關鍵字

開放街圖、知識本體、自願性地理資訊

Keywords

OpenStreetMap, Ontology, VGI

附件檔名

華芸線上圖書館

http://www.airitilibrary.com/Publication/Index?DocID=10218661-201803-201803260004-201803260004-61-69 201803-23-1-61-69

備註說明

N / A

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