福衛二號立體像對產製數值地表模型之適用性分析

Date
2009
Authors
莊宗達
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Abstract
福衛二號是國人自行研發設計的自主遙測衛星,在飛行過程中可進行前後左右不同角度的擺動,因此福衛二號可藉由前後擺動取得大範圍的同軌立體像對(along track stereo-pair),經後續影像處理後可產製出數值地表模型資料。因此本研究之目的為探討福衛二號立體像對產製數值地表模型之高程精度,以及地形因子對高程精度之關連性,並透過對以上兩者的探討,提出衛星立體像對所測繪產製之數值地形模型在實際運用上的適用性。 本研究以VRS-RTK現地測量資料進行精度檢測分析,現地測量獨立檢核點分析之結果,高程誤差量均方根值為3.76公尺、LE95為7.37公尺;現地測量連續檢核點分析之結果,高程誤差量均方根值為4.78公尺,LE95為9.87;利用5公尺數值航測DSM進行實驗比對檢測分析之結果,實證區的均方根值約介於4.19 ~ 5.38公尺間,LE95值介於8.22 ~ 10.54公尺間。 在誤差量空間分析方面,依據全域空間自相關與區域空間自相關分析之結果,福衛二號立體像對所產製之數值地表模型的高程誤差量在空間分佈上會有特例點(outliers)的差異的現象存在,而且高程誤差量較大的特例點出現比例會隨著坡度、地形崎嶇度等因子的提高而增加,且坡度>25度以上的區域,各坡向間的出現特例點的比例會有差異。因此在適用性方面,本研究提出三點建議: (1)人為建物部分因福衛二號立體像對本身空間解析度不足,以及高程精度只能監測樓層數較高的建築,因此較不適用。 (2)在地形影響方面,山脊、山谷等處有較大的高程誤差量出現,邊坡上的高程誤差量則需考慮到坡度-坡向的綜合影響,尤其在坡度較大的區域,各坡向間的誤差量會有差異存在。 (3)在崩塌地檢測方面,較適用於丘陵區或山區邊坡大規模的崩塌地崩塌量檢測。
Formosat-2 satellite is the Taiwan’s first developed and manageable remote sensing satellite. It can rotate in row/pitch direction and get stereo-pair、which can be used to extract DSM、form along-track rotation. The study has three aims. The first is to analyze the precision of the Formosat-2 DSM、which extracted from FORMOSAT-2 stereo-pair. And the Second is to analyze the relation to the FORMOSAT-2 DSM precision and the terrain element、Then point to the applicability of the Formosat2 DSM . In the study、the author first used the technology of the RTK-VRS to examine the precision of the Formosat2 DSM. The results of on-site static measure indicate that RMSE is 3.76m and LE95 is 7.37m. On the other hand、the results of on-site dynamic measure indicate that RMSE is 4.78m and LE95 is 9.87m. Secondly、the author used the digital aerial DSM to examine the precision of the four selection study area in Pa-kua Tableland、and the result indicates that RMSE is about 4.19m to 5.38m and LE95 is about 8.22 to 10.54. According to the analysis of the spatial autocorrelation、the author has found the elevation error of the Formosat2 DSM have spatial cluster phenomenon、called as outliers、in spatial distribution. And the outliers occurrence percentage are highly related to the terrain slope、roughness、and aspect which slope is greater than 25 degrees. The applicability of Formosat2 stereo pair generates DSM are as follows: (1) The Formosat2 DSM is not suitable to monitor the urban area. Because the Formosat2 image spatial resolution is not high enough to recognize the man-made building boundary and the elevation precision only can monitor the building which elevation is greater than 5m. (2)In the field of terrain effect、The Formosat2 DSM has more error on ridges and valleys. Moreover、the error on hillside should be considered with the slope-aspect effect、especially on steep area. (3)In the aspect of landslides monitoring、the Formosat2 DSM may be suitable to examine the landslides collapse volume.
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Keywords
福爾摩沙衛星二號立體像對, 數值地表模型, 空間自相關分析, Formasat2 Stereo Pair, Digital Surface Model, Spatial Autocorrelation
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