TWI477801B - Method of geospatial-related waveform analysis for full-waveform lidar - Google Patents
Method of geospatial-related waveform analysis for full-waveform lidar Download PDFInfo
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本發明係有關於一種全波形光達之空間關聯波形分析方法，尤指涉及一種光達測量領域及空間資訊領域，特別係指藉由考量波形間之空間相關性進整合分析，以提升光達森林地區之地面點數量，進而生產高精度之三維數值地面模型（Digital Elevation Model），以供環境議題分析使用之方法。The invention relates to a spatially correlated waveform analysis method for full-wavelength light, in particular to a field of optical measurement and spatial information, in particular to increase the optical reach by considering spatial correlation between waveforms. The number of ground points in the forest area, which in turn produces a high-precision Digital Elevation Model for use in environmental issues analysis.
無論光達（Light Detecting and Ranging, LiDAR）、環境議題或通信產業均有精密量測之需求。其中LiDAR主要應用為地形、模擬水流量、污染、城市規劃與建築使用；且該技術同時具有廣泛之軍事與情報應用。LiDAR之趨勢為降低成本與提高數據採集之效率。許多地圖業者結合LiDAR、遙感探測（Remote Sensing）及已漸趨成熟之知識理論，可提供更準確及更少程式編寫之圖像訊息。Whether it is Light Detecting and Ranging (LiDAR), environmental issues or the communications industry, there is a need for precision measurement. Among them, LiDAR is mainly used for terrain, simulated water flow, pollution, urban planning and building use; and the technology has a wide range of military and intelligence applications. The trend in LiDAR is to reduce costs and increase the efficiency of data collection. Many map operators combine LiDAR, Remote Sensing and the increasingly mature knowledge theory to provide more accurate and less programmed image information.
在波形分析方面，以全波形光達記錄連續回波訊號，使用者可進行波形分析（Waveform Analysis）以得到更豐富之地表資訊，進而有助於地表之重建與判釋。該波形分析為全波形光達資料處理中重要之工作項目，然而現有光達波形分析方法中，係利用單一回波訊號進行波形分析，以萃取波形參數及三維空間座標，然而在時間序列連續掃描之光達系統中，並未考量波形與波形之空間相關性（Geospatial Relationship）進行整合分析，因此未能偵測弱回波訊號。如美國專利編號US 6,861,974，其主要目的係降低雜訊對波形訊號之影響，然而方法上係使用單一回波之訊號，該發明未對空間關聯之訊號進行整合分析，因此無法偵測弱之波形訊號並降低雜訊之干擾。另外，中華民國發明第I334711號，係使用單一信號進行分析，以不同取樣點間隔分析單一一維訊號，而美國專利編號US 8,463,579之發明，亦使用單一信號進行分析，以貝氏（Bayesian）減少雜訊影響；然而前述兩項專利發明（中華民國發明第I334711號與US 8,463,579）皆未考量相鄰訊號處理。而美國專利編號US 8,368,876，此發明為發射單一雷射脈衝，雖可接收複數個回波訊號，以增加回波訊號之數量，但未進行回波訊號之弱訊號處理。In the aspect of waveform analysis, the continuous echo signal is recorded by the full waveform light, and the user can perform Waveform Analysis to obtain richer surface information, thereby contributing to the reconstruction and interpretation of the surface. The waveform analysis is an important work item in the whole waveform data processing. However, in the existing optical waveform analysis method, a single echo signal is used for waveform analysis to extract waveform parameters and three-dimensional coordinates, but continuous scanning in time series In the Guangda system, the spatial correlation between the waveform and the waveform (Geospatial Relationship) was not considered for integration analysis, so the weak echo signal could not be detected. For example, U.S. Patent No. 6,861,974, the main purpose of which is to reduce the influence of noise on the waveform signal. However, the method uses a single echo signal, and the invention does not integrate the spatially correlated signal, so the weak waveform cannot be detected. Signal and reduce noise interference. In addition, the Republic of China Invention No. I334711 uses a single signal for analysis to analyze a single one-dimensional signal at different sampling points. The invention of US Patent No. US 8,463,579 also uses a single signal for analysis, Bayesian. The noise effect is reduced; however, the two patent inventions (the Republic of China invention No. I334711 and US 8,463,579) do not consider adjacent signal processing. U.S. Patent No. 8,368,876, which discloses a single laser pulse, can receive a plurality of echo signals to increase the number of echo signals, but does not perform weak signal processing of the echo signals.
在波形展示方面，Persson等人於2005年所提之文獻（Persson, Å., Söderman, U., Töpel, J. and Ahlberg, S., 2005. Visualization and analysis of fullwaveform airborne laser scanner data. International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 36(3/W19): 103-108.）中，係將所有光達波形依空間位置進行展示，以觀察地表物體光達波形之目的，然而其研究僅針對多個波形之視覺化展示，無法進行波形分析。而中華民國發明第I348126號，此發明係使用離散點光達，降低光達點以提升展示效能，惟此空載離散點光達系統，為了減少資料儲存量，並不會記錄全部之回波，僅在硬體上進行單一回波之即時處理，最終只能記錄7個空間座標。In terms of waveform display, Persson, Å., Söderman, U., Töpel, J. and Ahlberg, S., 2005. Visualization and analysis of fullwaveform airborne laser scanner data. International Archives In the Photogrammetry, Remote Sensing and Spatial Information Sciences, 36(3/W19): 103-108.), all light waveforms are displayed according to the spatial position to observe the surface object light waveform, but its research Waveform analysis is not possible for visual presentation of multiple waveforms only. The Republic of China invented No. I348126, which uses discrete point light to reduce the light reaching point to improve display performance. However, the empty-load discrete point light system does not record all echoes in order to reduce data storage. Only one-time processing of a single echo is performed on the hardware, and only seven space coordinates can be recorded at the end.
在波形整合方面，Jutzi與Stilla於2005年所提之文獻（Jutzi, B., Stilla, U., 2005. Waveform processing of laser pulses for reconstruction of surfaces in urban areas. Measurement Techniques 2, 2.）中，係將同一掃描線之地面光達波形整合成二維矩陣，直接在二維矩陣偵測訊號強度較強之位置。由於此方法僅偵測訊號強度較強之位置，雖然可以萃取連續 地三維空間座標，然而受部份遮蔽之弱訊號（Weak Signal）仍然無法被偵測。而Yao與Stilla於2010年所提之文獻（Yao, W., Stilla, U., 2010. Mutual enhancement of weak laser pulses for point cloud enrichment based on full-waveform analysis. IEEE Transactions on Geoscience and Remote Sensing 48, 3571-3579.）中，則針對地面光達掃描之建築物訊號進行方向性之疊加，由於建築物之回波訊號連續且規則，故可偵測地面光達人造建築物之弱回波訊號。然而，自然地形並非規則之訊號，如森林區之地面點就因回波訊號較微弱而不易取得，故此方法對複雜空載光達掃描之森林訊號則不適用。此外，該方法無波形對位處理，必需測試每一個波形疊加可能為方向，因此運算量大。另外，Yang等人於2013年所提之文獻（Yang et al., 2013. Three-Dimensional Forest Reconstruction And Structural Parameter Retrievals Using A Terrestrial Full-Waveform Lidar Instrument, Remote Sensing of Environment, 135:36-51.）中，係使用地面全波形光達（Full Waveform Lidar）系統萃取森林參數，程序上係先對光達進行單一波形分析產生點座標及波形參數，再進行少量地面測量之森林參數與對應波形參數進行回歸（Regression），建立森林參數與波形參數之轉換關係，最後將所有波形參數轉換成森林參數進行分類。而Chhatkuli等人於同年提出之文獻（Chhatkuli el al., 2012. Full Waveform Lidar Exploitation Technique And Its Evaluation In The Mixed Forest Hilly Region, IAPRS XXXIX(B7):505-509.）中，亦使用全波形光達系統萃取森林區之點座標；惟上述兩項研究皆使用傳統之一維波形分析方法，可能會過度參數化（Over-Parameter），得到大量之非真實點。由於在大範圍之作業區域中，產生大量非真實點將會造成作業成本增加，以1幅1/5000基本圖（平均點密度為2點/m2 ）為例，原始點數量約為2500m*2700m*2點/m2 =13,500,000點，顯見資料量非常龐大。故以傳統方式偵測微弱訊號，可能造成過度參數化，而產生大量虛擬點。In terms of waveform integration, Jutzi, B., Stilla, U., 2005. Waveform processing of laser pulses for reconstruction of surfaces in urban areas. Measurement Techniques 2, 2. The ground light waveforms of the same scanning line are integrated into a two-dimensional matrix, and the two-dimensional matrix is directly detected at a position where the signal intensity is strong. Since this method only detects the position where the signal intensity is strong, although the continuous three-dimensional space coordinates can be extracted, the partially obscured Weak Signal can still be detected. Yao and W., Stilla, U., 2010. Mutual enhancement of weak laser pulses for point cloud enrichment based on full-waveform analysis. IEEE Transactions on Geoscience and Remote Sensing 48, In 3571-3579.), the directionality of the building signal for ground-light scanning is superimposed. Since the echo signal of the building is continuous and regular, it can detect the weak echo signal of the ground light reaching the artificial building. However, natural terrain is not a signal of rules. For example, the ground point of the forest area is not easy to obtain because the echo signal is weak. Therefore, this method does not apply to forest signals with complex no-load light scanning. In addition, this method has no waveform alignment processing, and it is necessary to test that each waveform superposition may be in a direction, so the amount of calculation is large. In addition, Yang et al., 2013. Three-Dimensional Forest Reconstruction And Structural Parameter Retrievals Using A Terrestrial Full-Waveform Lidar Instrument, Remote Sensing of Environment, 135:36-51. In the middle, the Full Waveform Lidar system is used to extract the forest parameters. The program first performs a single waveform analysis on the light to generate point coordinates and waveform parameters, and then performs a small amount of ground measurement on the forest parameters and corresponding waveform parameters. Regression establishes the conversion relationship between forest parameters and waveform parameters, and finally converts all waveform parameters into forest parameters for classification. In the same year, Chhatkuli et al. (Chhatkuli el al., 2012. Full Waveform Lidar Exploitation Technique And Its Evaluation In The Mixed Forest Hilly Region, IAPRS XXXIX (B7): 505-509.) also uses full-wavelength light. The system extracts the coordinates of the forest area; however, both of the above studies use the traditional one-dimensional waveform analysis method, which may over-parameterize and obtain a large number of non-real points. Since a large number of unreal points will cause an increase in operating costs in a wide range of work areas, taking a 1/5000 base map (average point density of 2 points/m 2 ) as an example, the number of original points is about 2500 m * 2700 m. *2 points / m 2 = 13,500,000 points, it is obvious that the amount of data is very large. Therefore, detecting weak signals in a conventional manner may cause excessive parameterization and generate a large number of virtual points.
鑑於傳統空載光達系統中，其空載全波形光達之載具為飛機，因此光達雷射掃描之位置及方向係隨時間而改變，即空間中之光達回波在三度空間中有不同之位置及角度，無法直接疊合分析。且在全波形光達之弱回波形訊號分析中，造成波形反射訊號減弱之主要因素係雷射訊號受部份遮蔽，而這類弱回波形訊號之能量雖比背景雜訊（Background Noise）高一些，但無法以傳統方法偵測。故，ㄧ般習用者係無法符合使用者於實際使用時之所需。In view of the traditional no-load optical system, the carrier of the no-load full-wavelength light is an aircraft, so the position and direction of the laser-to-laser scanning change with time, that is, the light in the space reaches the echo in the third space. There are different positions and angles in the middle, and it is impossible to directly superimpose the analysis. In the weak waveform signal analysis of the full waveform light, the main factor causing the waveform reflection signal to be weakened is that the laser signal is partially obscured, and the energy of such weak return waveform signal is higher than the background noise. Some, but not detectable by traditional methods. Therefore, the user-like users cannot meet the needs of the user in actual use.
本發明之主要目的係在於，克服習知技藝所遭遇之上述問題並提供一種整合空間關聯之多個波形訊號進行波形分析，而能有效萃取森林區之地面點之弱回波訊號，進而生產高精度之三維數值地面模型（Digital Elevation Model），以供環境議題分析使用之全波形光達之空間關聯波形分析方法。The main object of the present invention is to overcome the above problems encountered in the prior art and to provide a waveform analysis by integrating spatial waveforms of multiple waveform signals, thereby effectively extracting weak echo signals of ground points in the forest area, thereby producing high The Digital Elevation Model for Accuracy, a spatially correlated waveform analysis method for full-wavelength light used for environmental issues analysis.
本發明之次要目的係在於，提供一種改善穿透率較差區域之地表資訊，並降低背景雜訊（Background Noises）對弱回波之干擾之全波形光達之空間關聯波形分析方法。A secondary object of the present invention is to provide a spatial correlation waveform analysis method for improving the surface information of a region with poor transmittance and reducing the interference of background noises to weak echoes.
本發明之另一目的係在於，提供一種考量空間關聯訊號以偵測弱回波訊號，可增加資訊並避免過度參數化而能產生可靠地面點之全波形光達之空間關聯波形分析方法。Another object of the present invention is to provide a spatial correlation waveform analysis method that considers a spatially correlated signal to detect a weak echo signal, can increase information, and avoid excessive parameterization to generate a full-wavelength light of a reliable ground point.
為達以上之目的，本發明係一種全波形光達之空間關聯波形分析方法，其至少包含下列步驟：（Ａ）連結空間關聯性波形： 選定一回波訊號做為主波形，讀取主波形之記錄時間，並以記錄時間為 起始位置搜尋相鄰之波形訊號，再 以全球定位系統時間（GPS Time）對所有選定之波形進行排序，連結主波形與前一時刻及後一時刻掃描之空間關聯回波訊號，以形成時序之回波訊號；（Ｂ）萃取波形對位參考點：將已 排序之回波訊號經高斯平滑化過濾隨機誤差後，先偵測其局部最大值，以偵測極值點，若相鄰之極值點小於距離門檻，則過濾鄰近之極值點，再過濾靠近邊界之極值點，以降低邊界效應，若相鄰之極值點 遠小於背景雜訊，則過濾 遠小於背景雜訊之極值點，最後保留下來之點即為波形對位參考點；（Ｃ）波形對位及堆疊： 利用對位參考點，進行主波形及前、後波形之對位，將相鄰波形平移至相同參考基準完成波形對位，接著將對位後波形進行相加完成波形堆疊；以及（Ｄ）堆疊波形之分析：利用高斯分解法進行堆疊波形之資訊萃取，將堆疊波形分解為數個回波，萃取波形峰值、波形寬度及波形強度，並僅保留最後回波資訊，再分析堆疊波形與原始主波形之最後回波距離，以重複確認偵測成果正確性。For the purpose of the above, the present invention is a spatially correlated waveform analysis method for full-wavelength light, which comprises at least the following steps: (A) concatenating spatial correlation waveforms: selecting an echo signal as a main waveform, reading the main waveform Recording time, searching for adjacent waveform signals based on the recording time, and sorting all selected waveforms by GPS Time, connecting the main waveform with the previous and subsequent scans Spatially associated echo signals to form time-series echo signals; (B) Extracted waveform alignment reference points: After Gaussian smoothing of the sorted echo signals, the local maximum is detected first, to detect Measure the extreme point. If the adjacent extreme point is less than the distance threshold, filter the adjacent extreme point and filter the extreme point near the boundary to reduce the boundary effect. If the adjacent extreme point is much smaller than the background noise , the filtering is much smaller than the extreme point of the background noise, and the last point remaining is the waveform alignment reference point; (C) waveform alignment and stacking: using the alignment reference point The waveform and the alignment of the front and back waveforms, the adjacent waveforms are translated to the same reference reference to complete the waveform alignment, and then the waveforms after the alignment are added to complete the waveform stack; and (D) the analysis of the stacked waveforms: using Gaussian decomposition The information extraction of the stacked waveform is performed, the stacked waveform is decomposed into several echoes, the waveform peak value, the waveform width and the waveform intensity are extracted, and only the last echo information is retained, and then the final echo distance of the stacked waveform and the original main waveform is analyzed to repeat Confirm the correctness of the detection results.
於本發明上述實施例中，該步驟（Ｄ） 重複確認偵測成果正確性，係包含以下步驟：（ｄ１） 過濾重複萃取之回波，若堆疊波形偵測成果之主波形原始最後回波距離小於給定門檻值，則視為重複萃取並將該點刪除；以及（ｄ２） 假設中間主波形與前、後波形峰值連線之交點與堆疊波形最後回波距離大於給定門檻值，則視為錯誤萃取。In the above embodiment of the present invention, the step (D) repeatedly confirms the correctness of the detection result, and the method includes the following steps: (d1) filtering the echo of the repeated extraction, if the original waveform of the stacked waveform detection result is the original final echo distance Less than a given threshold, it is considered as repeated extraction and the point is deleted; and (d2) assuming that the intersection of the intermediate main waveform with the peak connection of the front and back waveforms and the final echo distance of the stacked waveform is greater than a given threshold, then For error extraction.
１‧‧‧線條
１１‧‧‧步驟（Ａ）連結空間關聯性波形
１２‧‧‧步驟（Ｂ）萃取波形對位參考點
１３‧‧‧步驟（Ｃ）波形對位及堆疊
１４‧‧‧步驟（Ｄ）堆疊波形之分析
２、３、４‧‧‧波形1‧‧‧Line 11‧‧‧Step (A) Linking Spatial Correlation Waveforms 12‧‧‧Step (B) Extraction Waveform Registration Reference Point 13‧‧‧Step (C) Waveform Alignment and Stacking 14‧‧ (D) Analysis of stacked waveforms 2, 3, 4‧‧‧ waveforms
第１圖，係本發明之流程示意圖。
第２圖，係本發明之空間關聯性波形示意圖。
第３圖，係本發明之萃取波形對位參考點示意圖。
第４圖，係本發明比較未對位及經過對位之波形示意圖。
第５圖，係本發明之波形堆疊示意圖。
第６圖，係本發明之波形堆疊示意圖
第７圖，係本發明之林區光達三維點雲示意圖。
Fig. 1 is a schematic flow chart of the present invention.
Figure 2 is a schematic diagram of the spatial correlation waveform of the present invention.
Figure 3 is a schematic diagram of the alignment reference point of the extracted waveform of the present invention.
Figure 4 is a schematic diagram showing the waveforms of the comparatively unaligned and aligned bits of the present invention.
Figure 5 is a schematic diagram of the waveform stacking of the present invention.
Fig. 6 is a schematic view showing a waveform stacking diagram of the present invention, which is a schematic diagram of a three-dimensional point cloud of the forest area of the present invention.
請參閱『第１圖～第５圖』所示，係分別為本發明之流程示意圖、本發明之空間關聯性波形示意圖、本發明之萃取波形對位參考點示意圖、本發明比較未對位及經過對位之波形示意圖、及本發明之波形堆疊示意圖。如圖所示：本發明係一種全波形光達（Full Waveform Light Detection and Ranging）之空間關聯（Geospatial Relationship）波形分析（Waveform Analysis）方法，係藉由考量波形間之空間相關性進行整合分析，以提升光達森林地區之地面點數量，進而生產高精度之三維數值地面模型（Digital Elevation Model），以供環境議題分析使用。本發明至少包含下列步驟：Please refer to FIG. 1 to FIG. 5 , which are schematic diagrams of the flow of the present invention, a schematic diagram of the spatial correlation waveform of the present invention, a schematic diagram of the reference waveform of the extracted waveform of the present invention, and a comparison of the present invention. The schematic diagram of the waveform of the alignment and the waveform stacking of the present invention. As shown in the figure, the present invention is a method of spatial waveform analysis (Wosformial Relationship) of Full Waveform Light Detection and Ranging, which integrates and analyzes the spatial correlation between waveforms. In order to increase the number of ground points in the forest area, a high-precision Digital Elevation Model is produced for analysis of environmental issues. The invention includes at least the following steps:
（Ａ）連結空間關聯性波形１１：選定一回波訊號做為主波形，讀取主波形之記錄時間，並以記錄時間為 起始位置搜尋相鄰之波形訊號，再 以全球定位系統時間（GPS Time）對所有選定之波形進行排序，連結主波形與前一時刻及後一時刻掃描之空間關聯回波訊號，以形成時序之回波訊號，如第２圖所示；(A) Link spatial correlation waveform 11: Select an echo signal as the main waveform, read the recording time of the main waveform, and search for the adjacent waveform signal with the recording time as the starting position, and then use the global positioning system time ( GPS Time) sorts all selected waveforms, and connects the main waveform with the spatial echo signals of the previous and subsequent scans to form a time-series echo signal, as shown in Figure 2;
（Ｂ）萃取波形對位參考點１２：將已 排序之回波訊號經高斯平滑化過濾隨機誤差後，先偵測其局部最大值，以偵測極值點，若相鄰之極值點小於距離門檻，則過濾鄰近之極值點，再過濾靠近邊界之極值點，以降低邊界效應，若相鄰之極值點 遠小於背景雜訊，則過濾 遠小於背景雜訊之極值點，最後保留下來之點即為波形對位參考點，如第３圖所示；(B) Extraction waveform alignment reference point 12: After filtering the randomized error of the sorted echo signal by Gaussian smoothing, first detect the local maximum value to detect the extreme value point, if the adjacent extreme value point is smaller than For the threshold, the nearest extreme point is filtered, and the extreme point near the boundary is filtered to reduce the boundary effect. If the adjacent extreme point is much smaller than the background noise, the filtering is much smaller than the extreme value of the background noise. The last remaining point is the waveform alignment reference point, as shown in Figure 3;
（Ｃ）波形對位及堆疊１３： 利用對位參考點，進行主波形及前、後波形之對位，將相鄰波形平移至相同參考基準完成波形對位，如第４圖所示，其中圖(a)為三個相鄰波形，包含 主波形及前、後波形，圖(b)為未對位之波形，及圖(c)為經過對位之波形； 接著將對位後波形進行相加完成波形堆疊，如第５圖所示，其中線條１為波形堆疊成果 ；以及(C) Waveform alignment and stacking 13: Using the alignment reference point, the main waveform and the front and back waveforms are aligned, and the adjacent waveforms are translated to the same reference reference to complete the waveform alignment, as shown in Fig. 4, wherein Figure (a) shows three adjacent waveforms, including the main waveform and the front and back waveforms, (b) is the unaligned waveform, and (c) is the aligned waveform; then the post-alignment waveform is performed. Adding the waveform stack together, as shown in Figure 5, where line 1 is the result of the waveform stacking;
（Ｄ）堆疊波形之分析１４：利用高斯分解法進行堆疊波形之資訊萃取，將堆疊波形分解為數個回波，萃取波形峰值、波形寬度及波形強度（如第５圖中線條１上之三角形為波形堆疊偵測之成果），並僅保留最後回波資訊，再分析堆疊波形與原始主波形之最後回波距離，以重複確認偵測成果正確性。其中，該 重複確認偵測成果正確性之方法，係包含以下步驟：(D) Analysis of stacked waveforms 14: Using Gaussian decomposition method to extract information of stacked waveforms, decompose the stacked waveform into several echoes, extract the peak value of the waveform, the width of the waveform and the intensity of the waveform (as shown in Figure 5, the triangle on line 1 is The result of the waveform stack detection), and only the last echo information is retained, and then the final echo distance of the stacked waveform and the original main waveform is analyzed to repeatedly confirm the correctness of the detection result. Among them, the method of repeatedly confirming the correctness of the detection result includes the following steps:
（ｄ１） 過濾重複萃取之回波，若堆疊波形偵測成果之主波形原始最後回波距離小於給定門檻值，則視為重複萃取並將該點刪除；以及(d1) filtering the echo of the repeated extraction, if the original final echo distance of the main waveform of the stacked waveform detection result is less than a given threshold, it is regarded as repeated extraction and deleting the point;
（ｄ２） 假設中間主波形與前、後波形峰值連線之交點與堆疊波形最後回波距離大於給定門檻值，則視為錯誤萃取。此原因為考慮空間關聯性，中間主波形與連線之交點應接近地表微弱回波位置，若相差太遠可能為因波形堆疊，雜訊值增強所萃取之錯誤點。(d2) Assuming that the intersection of the intermediate main waveform with the peak connection of the front and back waveforms and the final echo distance of the stacked waveform is greater than the given threshold, it is considered an error extraction. The reason for this is to consider the spatial correlation. The intersection of the intermediate main waveform and the connection should be close to the weak echo position of the surface. If the difference is too far, it may be the error point extracted by the waveform stack and the noise value enhancement.
如是，藉由上述揭露之流程構成一全新之全波形光達之空間關聯波形分析方法。If so, a new spatially correlated waveform analysis method for full waveform light is constructed by the above disclosed process.
請參閱『第６圖及第７圖』所示，係分別為本發明之波形堆疊示意圖、及本發明之林區光達三維點雲示意圖。如圖所示：本發明係整合空間中數個全波形光達之回波，並偵測及萃取數值地形模型所需之地面點。使用時，經由結合使用波形堆疊法，考慮鄰近波形具有高空間相關性，透過疊合鄰近波形，增強地表回波訊號，進行地表微弱回波偵測。如第６圖所示，圖中三角形為透過一維波形分析方法得到之峰值位置，而波形２在箭頭指向處有一微弱地表回波，惟使用一維波形分析法無法萃取得到此一弱回波訊號。故利用波形堆疊之概念疊合鄰近波形３與波形４，增強地表微弱回波訊號，以萃取地表點。使用本發明之實例分析以Leica ALS60之資料進行分析，測試區為複雜之森林區，如第７圖所示之林區光達三維點雲。表1為比較原始地面點、傳統一維波形分析方法（高斯分解法）及本發明波形堆疊分析方法之結果；由結果可知，本發明之波形堆疊分析方法在森林區萃取效果最佳，可增加85%之地面點，顯示本發明之波形堆疊分析方法可豐富穿透率較差區域之地表資訊，達到提升森林區數值地形模型之地面點數量。實驗亦證明，本方法較現有之技術（一維波形分析）能萃取更多之地面點。Please refer to FIG. 6 and FIG. 7 respectively, which are schematic diagrams of waveform stacking of the present invention, and a schematic diagram of a three-dimensional point cloud of the forest area of the present invention. As shown in the figure: The present invention integrates echoes of a plurality of full-wavelength light in a space and detects and extracts ground points required for a numerical terrain model. In use, by using the waveform stacking method, considering the high spatial correlation of the adjacent waveforms, the surface echo signals are enhanced by superimposing the adjacent waveforms, and the surface weak echo detection is performed. As shown in Fig. 6, the triangle in the figure is the peak position obtained by the one-dimensional waveform analysis method, and the waveform 2 has a weak surface echo at the arrow pointing, but this weak echo cannot be extracted by the one-dimensional waveform analysis method. Signal. Therefore, the concept of waveform stacking is used to superimpose adjacent waveform 3 and waveform 4 to enhance the surface weak echo signal to extract surface points. Analysis using the example of the present invention was carried out by analyzing the data of Leica ALS60, which is a complex forest area, such as the three-dimensional point cloud in the forest area shown in Fig. 7. Table 1 shows the results of comparing the original ground point, the conventional one-dimensional waveform analysis method (Gaussian decomposition method) and the waveform stack analysis method of the present invention; from the results, the waveform stack analysis method of the present invention has the best extraction effect in the forest area, and can be increased. 85% of the ground point shows that the waveform stack analysis method of the present invention can enrich the surface information of the region with poor penetration rate, and achieve the number of ground points for improving the numerical terrain model of the forest area. Experiments have also shown that this method can extract more ground points than the existing technology (one-dimensional waveform analysis).
表1Table 1
本發明之技術特徵包含： The technical features of the present invention include:
1.整合空間關聯之多個波形訊號進行波形分析：現行光達掃描頻率極高（以Leica ALS 70為例可達每秒50萬點），因掃描快速，所以相鄰波形訊號距離近，故相關性高，可整合空間關聯之波形訊號進行波形分析。主要係堆疊空間相鄰之光達波形於波形分析，並進行波形對位以正確堆疊空間關聯之光達回波波形。1. Integrate spatial waveforms with multiple waveform signals for waveform analysis: the current optical scanning frequency is extremely high (using the Leica ALS 70 as an example to reach 500,000 points per second). Because of the fast scanning, the adjacent waveform signals are close, so High correlation, waveform analysis can be integrated by spatially correlated waveform signals. Mainly in the stacking space adjacent to the light waveform in the waveform analysis, and the waveform alignment to correctly stack the space associated with the light echo waveform.
2.有效萃取森林區之地面點之弱訊號：本發明疊合相鄰訊號，增顯地面弱回波訊號，可有效萃取可靠之地面點弱回波訊號。此外，經波形分析後，並與原始相鄰波形比對檢核成果之合理性，以萃取地形分析所需之地面點。2. Effectively extracting the weak signal of the ground point of the forest area: The present invention superimposes the adjacent signal to increase the ground weak echo signal, and can effectively extract the reliable ground point weak echo signal. In addition, after waveform analysis, the rationality of the check results is compared with the original adjacent waveforms to extract the ground points required for terrain analysis.
本發明之主要功能包含：The main functions of the present invention include:
1. 降低背景雜訊（Background Noises）對弱回波之干擾：本發明技術重點為堆疊及分析，並提出波形對位（Waveform Alignment）之程序，可在堆疊空間中不同位置及不同方向之數個光達波形時，增顯（enhance）弱回波之訊號，並降低因背景雜訊所造成之錯誤點，進而克服疊加錯誤之問題。1. Reduce the interference of background noises on weak echoes: The technology of the present invention focuses on stacking and analysis, and proposes a program of Waveform Alignment, which can be in different positions and directions in the stacking space. When the light reaches the waveform, the signal of the weak echo is enhanced, and the error caused by the background noise is reduced, thereby overcoming the problem of the overlay error.
2.改善穿透率較差區域之地表資訊：本發明可偵測複雜波形訊號之弱回波，能有效增加森林區之地面點，提升其可靠地面點之數量，以豐富穿透率較差區域之地形。2. Improving surface information in areas with poor penetration: The present invention can detect weak echoes of complex waveform signals, can effectively increase the ground point of the forest area, and increase the number of reliable ground points to enrich the area with poor penetration rate. terrain.
由上述可知，本發明考量鄰近波形之空間關係，堆疊鄰近波形以提升可靠之地面點弱回波訊號，能有效萃取微弱地表回波資訊，重建完整三維數值地面模型。本方法主要包含四步驟：連結空間關聯性波形；萃取波形對位參考點；波形對位及堆疊；以及堆疊波形之分析。藉此，本發明利用原始之光達波形訊號，使用相鄰訊號進行處理，以空間關聯訊號可偵測弱回波訊號且降低雜訊之干擾，並增加點座標及波形參數等資訊，能避免過度參數化即能產生可靠之地面點並提升地面點數量，使地形分析更可靠，進而可在實務模式分析中應用於複雜之森林區，增顯地面弱回波訊號，可有效萃取可靠之地面弱回波訊號，以提供更可靠之成果。It can be seen from the above that the present invention considers the spatial relationship of adjacent waveforms, stacks adjacent waveforms to enhance the reliable ground point weak echo signals, can effectively extract weak surface echo information, and reconstruct a complete three-dimensional numerical ground model. The method mainly comprises four steps: linking a spatial correlation waveform; extracting a waveform alignment reference point; waveform alignment and stacking; and analyzing the stacked waveform. Therefore, the present invention utilizes the original light waveform signal and uses adjacent signals for processing, and the spatial correlation signal can detect weak echo signals and reduce noise interference, and increase information such as coordinates and waveform parameters, thereby avoiding Excessive parameterization can generate reliable ground points and increase the number of ground points, making terrain analysis more reliable, and then can be applied to complex forest areas in practical mode analysis, increasing ground weak echo signals, and effectively extracting reliable ground. Weak echo signals to provide more reliable results.
綜上所述，本發明係一種全波形光達之空間關聯波形分析方法，可有效改善習用之種種缺點，藉由考量波形間之空間相關性進整合分析，以提升光達森林地區之地面點數量，進而生產高精度之三維數值地面模型（Digital Elevation Model），以供環境議題分析使用，進而使本發明之産生能更進步、更實用、更符合使用者之所須，確已符合發明專利申請之要件，爰依法提出專利申請。In summary, the present invention is a spatially correlated waveform analysis method for full-wavelength light, which can effectively improve various shortcomings of the conventional use, and considers the spatial correlation between the waveforms to integrate and analyze to improve the ground point of the Guangda forest area. Quantity, and then the production of high-precision 3D numerical Elevation Model for environmental issues analysis, so that the production of the present invention can be more advanced, more practical, more in line with the needs of users, and indeed meet the invention patent For the requirements of the application, the patent application is filed according to law.
惟以上所述者，僅為本發明之較佳實施例而已，當不能以此限定本發明實施之範圍；故，凡依本發明申請專利範圍及發明說明書內容所作之簡單的等效變化與修飾，皆應仍屬本發明專利涵蓋之範圍內。However, the above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto; therefore, the simple equivalent changes and modifications made in accordance with the scope of the present invention and the contents of the invention are modified. All should remain within the scope of the invention patent.
11‧‧‧步驟(A)連結空間關聯性波形 11‧‧‧Step (A) Linking Spatial Correlation Waveforms
12‧‧‧步驟(B)萃取波形對位參考點 12‧‧‧Step (B) Extracting waveform alignment reference point
13‧‧‧步驟(C)波形對位及堆疊 13‧‧‧Step (C) Waveform alignment and stacking
14‧‧‧步驟(D)堆疊波形之分析 14‧‧‧Step (D) Analysis of stacked waveforms
Claims (2)
（Ａ）連結空間關聯性波形：選定一回波訊號做為主波形，讀取主波形之記錄時間，並以記錄時間為起始位置搜尋相鄰之波形訊號，再以全球定位系統時間（GPS Time）對所有選定之波形進行排序，連結主波形與前一時刻及後一時刻掃描之空間關聯回波訊號，以形成時序之回波訊號；
（Ｂ）萃取波形對位參考點：將已排序之回波訊號經高斯平滑化過濾隨機誤差後，先偵測其局部最大值，以偵測極值點，若相鄰之極值點小於距離門檻，則過濾鄰近之極值點，再過濾靠近邊界之極值點，以降低邊界效應，若相鄰之極值點小於背景雜訊，則過濾小於背景雜訊之極值點，最後保留下來之點即為波形對位參考點；
（Ｃ）波形對位及堆疊： 利用對位參考點，進行主波形及前、後波形之對位，將相鄰波形平移至相同參考基準完成波形對位，接著將對位後波形進行相加完成波形堆疊；以及
（Ｄ）堆疊波形之分析：利用高斯分解法進行堆疊波形之資訊萃取，將堆疊波形分解為數個回波，萃取波形峰值、波形寬度及波形強度，並僅保留最後回波資訊，再分析堆疊波形與原始主波形之最後回波距離，以重複確認偵測成果正確性。A spatially correlated waveform analysis method for full waveform light, comprising at least the following steps:
(A) Link spatial correlation waveform: select a echo signal as the main waveform, read the recording time of the main waveform, and search for the adjacent waveform signal with the recording time as the starting position, and then use the global positioning system time (GPS). Time) sorts all selected waveforms, and associates the main waveform with the spatial echo signals of the previous and subsequent scans to form a timing echo signal;
(B) Extracting the waveform alignment reference point: After filtering the randomized error of the sorted echo signal by Gaussian smoothing, first detect the local maximum value to detect the extreme value point, if the adjacent extreme value point is smaller than the distance Threshold, filter the neighboring extreme points, and then filter the extreme points close to the boundary to reduce the boundary effect. If the adjacent extreme points are smaller than the background noise, the filtering is less than the extreme point of the background noise, and finally remains. The point is the waveform alignment reference point;
(C) Waveform alignment and stacking: Using the alignment reference point, the main waveform and the front and back waveforms are aligned, and the adjacent waveforms are translated to the same reference reference to complete the waveform alignment, and then the post-alignment waveforms are added. Complete waveform stacking; and (D) analysis of stacked waveforms: use Gaussian decomposition to extract information from stacked waveforms, decompose the stacked waveform into several echoes, extract waveform peaks, waveform widths, and waveform intensities, and retain only the last echo information Then, analyze the final echo distance of the stacked waveform and the original main waveform to repeatedly confirm the correctness of the detection result.
（ｄ１） 過濾重複萃取之回波，若堆疊波形偵測成果之主波形原始最後回波距離小於給定門檻值，則視為重複萃取並將該點刪除；以及
（ｄ２） 假設中間主波形與前、後波形峰值連線之交點與堆疊波形最後回波距離大於給定門檻值，則視為錯誤萃取。According to the space-correlation waveform analysis method of the full-wavelength light described in the first claim of the patent scope, the step (D) repeatedly confirms the correctness of the detection result, and the following steps are included:
(d1) filtering the echoes of the repeated extraction, if the original final echo distance of the main waveform of the stacked waveform detection result is less than a given threshold, it is regarded as repeated extraction and deleting the point; and (d2) assuming the intermediate main waveform and The intersection of the front and back waveform peak connections and the final echo distance of the stacked waveform is greater than the given threshold, which is considered an error extraction.
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| TW200811759A (en) * | 2006-08-25 | 2008-03-01 | Hon Hai Prec Ind Co Ltd | System and method for filtering a point cloud |
| TW200828864A (en) * | 2006-12-29 | 2008-07-01 | Ind Tech Res Inst | Symbol rate testing method based on signal waveform analysis |
| CN101196562B (en) * | 2007-12-14 | 2012-01-04 | 武汉大学 | Method for laser radar waveshape data decomposition based on improved EM algorithm |
| US8368876B1 (en) * | 2008-10-17 | 2013-02-05 | Odyssey Space Research, L.L.C. | Calibration system and method for imaging flash LIDAR systems |
| CN103197321A (en) * | 2013-03-22 | 2013-07-10 | 北京航空航天大学 | Full-waveform laser radar system |
| CN103217679A (en) * | 2013-03-22 | 2013-07-24 | 北京航空航天大学 | Full-waveform laser radar echo data gaussian decomposition method based on genetic algorithm |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TWI710786B (en) * | 2015-04-07 | 2020-11-21 | 美商Ｇｍ全球技術有限公司 | A lidar system,an utilizing method of lidar and a vehicle assistance system thereof |
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