臺灣地形起伏劇烈且構造活動頻繁，高程基準的長期維護對各類測量與基礎建設至關重要。臺灣現行法定高程基準為2001臺灣高程基準（TaiWan Vertical Datum 2001, TWVD2001）係採用單一潮位站（基隆站1957–1991年）之平均海水位作為唯一水準零點。然而，臺灣四面環海，周邊海域受洋流與季風支配，海水面地形（Sea Surface Topography, SST）具備顯著的空間異質性。現行高程系統由單一水準零點向全島外推，忽略了區域海水面差異，易在遠離基隆之地區累積系統性誤差，進而造成高程基準的傾斜與偏移。有鑑於此，本研究旨在探討 TWVD2001採用單一水準零點之空間侷限性，並評估採用「分區水準網平差」策略作為替代方案之可行性。
為達成上述目的，本研究主要分為三個步驟。首先選取臺灣本島21個長期潮位站觀測紀錄，利用動態大氣壓力改正（Dynamic Atmospheric Correction, DAC）資料與衛星測高（Satellite Altimetry）資料，進行逆氣壓效應與地表垂直運動（Vertical Land Motion, VLM）改正，據以推算出 2025.0 曆元之長期平均海水位(Mean Sea Level, MSL)成果，作為後續水準網平差之約制水準零點；同時，整合臺灣一等水準網觀測資料。考量西南沿岸地層下陷嚴重且缺乏完整之一等水準網資料，本研究剔除麥寮、東石及四草等3處潮位站，保留剩餘18個潮位站水準點納入水準網中，再分別採用自由網平差與帶有隨機約制之高斯-馬可夫模型平差進行整體網形分析。最後，將各潮位站平差之高程成果差值與海洋平均動力地形（Mean Dynamic Topography, MDT）差值進行交叉對比分析，藉此釐清高程基準偏移之空間特徵與背後的物理機制。
潮位資料處理與MSL估算成果顯示，若資料品質優良且長度充足，利用算術平均法與六參數擬合法所推算之長期MSL具備高度一致性，全臺21站之最大差值僅為 4 mm，證實兩種數學估算模型在計算長期 MSL時均具備高度的一致性與穩定性。然而，將各站推算之2025.0曆元MSL與TWVD2001進行比對，發現各站MSL相對於TWVD2001有-74 mm至+371mm 的顯著差值。其中以南部後壁湖站與西南部四草站之偏差最為顯著，兩者之海平面高度皆較基隆水準原點高出340 mm以上，證實臺灣四周海域之海平面並非單一幾何等位面。
在平差成果方面，自由網平差與最小約制平差之後驗單位權中誤差皆通過 95% 信心區間的卡方測試，證實我國現行一等水準觀測資料品質均衡且網形幾何強度穩健。然而，當依序代入18個潮位站水準點約制值進行最小約制平差時，全網最高點與最低點的高程估值在約制不同水準零點的情況下之最大差值高達 440 mm，展現出顯著的誤差累積效應，且整體偏差呈現「由北向南、由東向西遞增」之空間變化趨勢。
最後，為量化不同潮位站MSL約制對臺灣高程系統所造成之影響，本研究分別以18個潮位站水準點為約制點執行最小約制平差，並提取基隆潮位站水準點(TG01)之高程估值進行交叉比對。平差成果顯示，各水準點約制下之TG01高程估值存在顯著的差異，其高程差值範圍介於-0.20 m至+0.24 m，整體落差達到0.44 m。此量化成果充分證明，區域性的高程差異已不容忽視；現行單一水準零點約制的方式，無法如實反映當地之平均海水位。針對上述侷限，本研究提出「分區水準網平差」之改善策略。根據基準偏移之空間分布趨勢，並結合縣市界，初步將全臺劃分為「北/東北沿岸區」、「東部沿岸區」、「西北沿岸區」、「西南/南部沿岸區」及「中部區域」五大區。本研究成功揭示了臺灣現行高程基準在全島尺度的系統性傾斜趨勢，不僅量化了各區域的基準偏移量，更為我國未來實施分區水準平差、以及高程基準的現代化革新提供了不可或缺的量化證據。

The Taiwan Vertical Datum 2001 (TWVD2001) relies on a single datum benchmark, K999, located at the Keelung tide gauge station. However, shaped by strong ocean currents and monsoons, the actual sea surface around Taiwan may not behave as a flat geometric plane. This research evaluates the spatial limitations of this single-point system and proposes a "sub-network adjustment" strategy as a practical alternative. By comparing the 2025.0 epoch MSL values at the tide gauge stations against the official TWVD2001 datum, we confirmed that the ocean surface surrounding Taiwan is indeed not a flat geometric plane. To evaluate the impact of this non-equipotential ocean surface on the terrestrial framework, we integrated these sea-level baselines into the first-order leveling network through Gauss-Markov adjustments. The results demonstrate that shifting the absolute height origin triggers severe distance-dependent error propagation, causing orthometric heights across the national framework to shift up to 440 mm. This strong spatial correlation between the magnitude of height shift and distance from the datum point indicates that the nationwide reference tilt is governed by real ocean physics rather than random measurement errors. To preserve local sea-level characteristics while resolving these spatial distortions, we suggest dividing Taiwan into five distinct vertical sub-networks. Ultimately, this study provides critical quantitative measurements and a mathematical foundation to help Taiwan modernize its vertical datum from a single static system to a multi-zone framework.

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