以幾何推論法融合光達資料與航攝影像進行建物屋頂面重建

Abstract

近年來光達 (Light Detecting And Ranging, LiDAR)系統已成為快速收集地表資訊的有效工具之一。由於光達點雲資料的離散特性，其對於地、物邊緣線描述之精度遠不如展現面狀特徵的優勢；而對於航攝影像而言，影像地面解析度高且具備豐富的輻射資訊故有利於邊緣之偵測。本研究嘗試結合這兩種資料來源進行三維建物屋頂面重建，研擬之演算法包括以下資料及步驟：(1)由光達資料提供近似三維房屋邊線，(2)建立光達三維房屋邊線之間的拓樸關係，(3)將光達房屋線條倒投影回對應的立體影像中，(4)利用二維以及三維幾何推論法篩選由影像萃取之邊緣線，(5)進行整體平差計算以合併房屋邊線完成屋頂面重建。實驗結果顯示，融合光達點雲資料萃取的房屋邊緣線條與影像邊緣線確能助益於建物屋頂面重建的作業。

The advent of LiDAR technique has opened up many possibilities for the purpose of object/surface reconstruction. The direct geo-referencing of 3-D laser point towards surface or terrain apparently outperforms photogrammetric method by employing at least two overlapping images in the data acquisition favor. It is, however, still inevitable to see some weaker characteristics of LiDAR system as compared to photogrammetric relatively high ground resolution and richer radiometric content revealed from the images. Therefore, fusion of above two data sets by utilizing mutual strengths for the purpose of reconstructing spatial information can be certainly optimistic and foreseen. The designed steps of building roof reconstruction are carried out by: (1). Hypothesizing 3-D building boundaries from LiDAR data set by edge detection; (2). Constructing the topological relationship of 3-D building boundaries; (3). Back-projecting hypothesized 3-D building boundaries onto the associated photos; (4). Validation of building boundaries by imposing 3-D geometric inference among intersected conjugate lines of candidates found in the images; (5). Merging and adjusting building boundaries. The results show that the proposed system offers more robust and satisfactory building reconstruction result as compared to the situation when only single data set is attempted.