臺灣地區因地形特殊，不僅有山地、丘陵及平原地區，還有許多離島分佈於本 島周圍，為了因應這樣的地理環境，臺灣有各種不同類型的重力資料，其中陸測重 力資料的空間分布及品質更是區域大地起伏模型達到公分級精度的主要條件，重新 對陸測重力資料進行網行平差之後，不僅剔除其中 67 筆粗差，平差後重力資料的 平均精度約 0.04mGal。受限於陸測重力資料在中央山區蒐集不易，藉由漸進式整合 法將空載資料填補至中央山區路測重力資料稀少的區域，已有效改善位於山區的 central 及 south 兩條檢核線的大地起伏模型達約 5 公分以內的精度，然而，礙於現 有 GPS/leveling 皆呈線狀分布且分布不均，無法全面評估模型精度。
混合型大地水準面模式的精度為決定高程現代化應用範圍的關鍵項目之一，目 前台灣 GPS/Leveling 資料不足且皆為線狀分布，對於評估大地水準面模式整體的精 度及台灣混合型大地水準面模式的計算皆嫌不足。反觀台灣目前 e-GPS 系統各測站 具有分布均勻且連續觀測的特性，是提供檢核資料的良好工具。建議應全面進行 e-GPS 的正高測量作業，其高精度(cm 級)且分布均勻的特性除了增加此系統服務的 多樣化，對於台灣混合型大地水準面模式的發展更有著莫大的幫助。
誌謝
本研究由內政部地政司，內政部國土測繪中心及國科會贊助。本文之大地水準面模 式網格可自內政部地政司取得。
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