數值影像製圖品質指標之研究

Abstract

隨著數值航測及遙感探測技術的發展，影像在製圖應用之潛力已日益提昇。影像之獲取受感測器、大氣環境、時間及資料處理等因素影響而有品質上之差異，影像品質之優劣直接影響製圖之應用。 數值影像製圖品質指標為衡量數值影像在製圖應用之品質評估。本研究以影像灰階分佈分析、邊緣線擷取分析、熵值及變異元等指標，針對SPOT衛星多光譜與全色態影像、航空照片正片與像片掃瞄影像及航空照片有雲層遮蔽與無雲層遮蔽掃瞄影像等三種相對品質影像，探討指標對影像品質評估之適用性。從評估結果顯示，變異元及邊緣線擷取指標，較能符合目視評估的結果。

The potential of mapping with digital images is growing as a result of the new development in digital photogrammetry and remote sensing. Images of different qualities are obtained from different sensors, atmospheric conditions, times and data processing methods. The quality of the images will affect their use for mapping. The mapping quality indices of digital images are used to evaluate the qualities necessary for mapping. Four evaluation schemes, namely, gray level distribution analysis, edge extraction analysis, entropy value and variogram analysis are investigated. This research compares different indices for the evaluation of a scene of SPOT panchromatic and multispectral images, scanned images from the diapositive and paper print of aerial photographs, and a pair of images scanned from diapositive with and without cloud. The resulting conclusion is that the indices from variogram analysis and edge extraction have better agreement with evalutation result from visual inspection.